Platinum CV3 - Cavity Drain Waterproof Membrane (3mm Stud)

Health & Safety And Installer Competency

Platinum CV3 forms part of a specialist structural waterproofing system and should be designed and installed by competent people experienced in cavity drain membrane work. The installation must follow the current CV3 product information, instructions for every ancillary and the project-specific waterproofing design.

Before work begins, confirm the structure, expected water conditions, internal environmental grade, drainage layout, outlet or sump position, pump duty, discharge route, ventilation strategy, final finishes and future maintenance access. A specialist survey is necessary for retaining structures so the moisture mechanism, structural defects, contamination and any separate remedial work are identified.

Wear appropriate PPE, including gloves, eye protection and safety footwear. Use suitable dust extraction and respiratory protection during drilling or substrate preparation. Provide correctly erected access equipment for high walls, arches and vaults, and keep the work area well lit and clear of loose rolls, open channels and trip hazards.

Scan for concealed electrical cables, gas pipes, water services and structural hazards before drilling. Control cutting tools, hammers, SDS drills and heat guns carefully. A heat gun may help dry the membrane surface or improve tape adhesion in cold or damp conditions, but the HDPE and butyl products must not be overheated or exposed to flame.

System Design Principles

CV3 is not resistant to hydrostatic pressure as installed. Its studded sheet, sealed fixings, joints and drainage components form a depressurised cavity that accepts and controls water entering through the structure. The building should still limit ingress so the quantity never exceeds the designed cavity, channel, sump, pump or outlet capacity.

The waterproofing designer must assess retaining conditions, groundwater risk, construction type, permeability, wall and slab junctions, movement joints, cracks, service penetrations, slab levels, internal use and acceptable consequence of failure. Consider combined forms of waterproofing where the site risk, structure or intended environment requires additional resilience.

Every part of the cavity must connect continuously to drainage. The wall membrane, floor membrane, AquaTrack, Floor Drain, outlets, sumps and discharge pipework should form a coordinated route without sealed pockets, backfalls, trapped sections or details that direct water onto a joint. The shallow 3mm cavity makes cleanliness and continuity particularly important.

Where pumping is essential, the design should consider duty and standby pumps, separate electrical supplies where appropriate, high-water alarms, battery back-up, telemetry and safe discharge. Receiving drainage must accept the design flow without surcharging, freezing or returning water towards the protected structure.

Suitable Substrates And Finishes

CV3 must be installed against a background stable enough to accept the specified fixing and support the final construction. Active structural movement, hazardous contamination, collapsing masonry and defects requiring engineered repair must be resolved before the membrane is concealed.

Preparation Of Walls, Floors And Soffits

Complete a specialist survey and remedy major sources of water ingress that can reasonably be corrected. Repair structural defects, active leaks, defective services, cracks and unstable backgrounds in accordance with the project design. Stop suitable local water leaks with Platinum Aqua Stop where appropriate, without confusing temporary leak control with the permanent drainage strategy.

Remove unsound plaster, render and screed. Stiff-brush the exposed substrate to remove loose material, laitance, salts, dust, mould, adhesive and organic debris. Sound existing render may remain where the surveyor and fixing specification accept it, but soft, friable or poorly bonded layers must not be relied upon to retain plugs or support finishes.

Treat appropriate fungal contamination in masonry with Lignum Pro M50 in accordance with its label and technical instructions. Active dry rot, wet rot, timber decay or insect attack requires specialist assessment and a complete remedial specification; simply covering affected materials with CV3 is not acceptable.

Make good severe depressions, open joints and unstable areas with Platinum Fillet Seal Mortar or a compatible 3:1 sand-and-cement mix containing Wykamol RenderProof where specified. A concrete base receiving board directly over the membrane should have a maximum departure of 5mm beneath a 2m straightedge. Allow repair and levelling materials to reach the condition required by their separate instructions before covering.

Apply Wykamol Anti-Lime Sealer to suitable concrete where free lime or dust could migrate into the cavity and drainage system. Keep the prepared surface and AquaTrack route free from mortar, drilling debris and sharp projections because blockage or puncture can compromise the shallow cavity.

Anti-lime sealer being applied to prepared concrete before installation of Platinum CV3 Waterproof Membrane.

Tools And Ancillary Products Required

Typical installation equipment includes a tape measure, straightedge, spirit or laser level, marker, sharp utility knife, scissors or shears, 110V SDS hammer drill, suitable 10mm masonry bits, club hammer or mallet, hand roller, clean cloths, stiff brush, vacuum or dust extraction, and a controlled hot-air gun for drying and assisting butyl adhesion where necessary. Vaults and high walls also require appropriate scaffold or access equipment.

Set out all Platinum Waterseal Brick Plugs, Waterseal Rope, Joint Sealing Membrane Tape, 150mm Corner Tape, AquaTrack components, repair products and protection materials before work starts. Confirm that roll sizes, fixing quantities, tape lengths, channel fittings, outlets, pumps and alarms match the drawings and calculated wastage. Do not improvise critical joints with generic tapes, mastics or sealants that have not been accepted for the detail.

Tools must be clean and serviceable. Dull blades can tear the membrane, worn drill bits can oversize holes, and contaminated rollers or cloths can reduce tape adhesion. Keep butyl surfaces clean and use firm, even pressure throughout each seal. Heat should assist drying and tack only; it must not distort the studs or soften the membrane.

Drainage Requirements

Below-ground CV3 installations must include a dependable method of disposing of water that may collect behind or beneath the membrane. Floors require a drainage outlet and a suitable fall towards it, or an AquaTrack perimeter drainage system connected to a safe gravity outlet or correctly sized AquaSump arrangement.

AquaTrack Drainage Channel is normally positioned at the vulnerable wall-to-floor junction, while AquaTrack Floor Drain Channel can provide cross-floor routes, threshold details or a connection to a central sump. The channel layout must collect water from every membrane cavity and structural junction without relying on water to cross unplanned obstructions or sealed pockets.

Provide inspection and jetting access at suitable locations, including changes of direction and channel runs that require future cleaning. Covers and access ports must remain reachable after screed, flooring, dry lining and joinery are completed. Record their locations before concealment and include them in the owner’s maintenance information.

If pumps are required, calculate inflow, duty point, static head, friction losses, discharge distance and chamber volume. Consider pump redundancy, high-water alarms, power-loss resilience and telemetry according to risk. The final discharge point must be lawful, dependable and arranged so water cannot flow back towards the building.

Platinum AquaTrack Channel positioned at the wall-to-floor junction to collect water from behind Platinum CV3 Waterproof Membrane, with Platinum Corner Tape securing the channel to the Newton Condensation Strip and Newton CDM Fibran XPS 500-C Insulation beneath (via Platinum CV3 Waterproof Membrane as a floor membrane).

Platinum AquaTrack Preparation And Installation

Form the AquaTrack route at the wall-to-floor junction in accordance with the current AquaTrack instructions and project drawings. The supporting bed must be stable and level, and the channel must not be distorted or obstructed by mortar, debris or uneven infill. Position the upstand against the wall-membrane detail so collected water can enter the channel freely.

Join channel lengths with AquaTrack Connector Pieces. Use Swept Corners at 90° direction changes, T-Pieces where perimeter and cross-floor runs meet, and AquaTrack Floor Drain where a channel without a wall upstand is required. Connect the selected Universal End Cap, 110mm Outlet or approved 90° In-Line Connector to compatible pipework leading towards the sump or gravity discharge.

Install AquaTrack Inspection Ports and In-Line Access Ports where the maintenance design requires them, ensuring each remains reachable after the final floor build-up. Keep internal channel surfaces clean and check that each connection presents an uninterrupted flow path. Do not rely on adhesive, foam or improvised fittings that could create an internal lip or detach later.

Before concealing the drainage system, flush it with clean water and confirm flow to the outlet or AquaSump. Inspect joints, corners, access points and discharge pipework, then photograph and record the installed layout. Where a pump is fitted, test normal operation, alarm function, back-up provision and discharge under controlled conditions.

Wall Installation

CV3 may be installed vertically or horizontally. Measure the wall carefully and cut the roll on a clean, protected surface with a sharp knife, scissors or shears. Position the sheet with the studs towards the wall and the flat face towards the room, keeping it level and tight into corners without excessive stretching, bridging or distortion.

Begin at the top of the wall and make sufficient initial fixings to support the sheet before completing the chosen fixing pattern. Drill a 10mm hole centrally through a membrane stud and into sound masonry to the depth required by the Platinum Waterseal Brick Plug. Minimise drilling dust behind the sheet and avoid striking edges between studs.

Insert a Waterseal Brick Plug With Seal and drive it fully home so the sealing washer compresses evenly against the membrane. Where a plug without a seal and Platinum Waterseal Rope detail is specified, form a continuous ring around the plug so the butyl compresses into a watertight gasket. Reject loose or poorly sealed fixings and repair the location correctly.

Continue the membrane into ceiling voids and down to the floor or drainage detail where possible. Return it onto adjacent walls sufficiently to isolate the final lining, and plan openings before fixing. Electrical points, cables, pipework and switches should remain on the dry side wherever practicable.

Wall Fixing Centres And Internal Finishes

Fixing density depends on the selected dry-lining system and substrate. For preservative-treated timber battens, use centres no greater than 600mm vertically and 400mm horizontally. A compatible fixed metal track may use centres no greater than 800mm vertically and 600mm horizontally. Barrel-vault details require tighter fixing, typically 300mm around the vault and 600mm down its length.

Use preservative-treated timber battens at least 25mm x 38mm, with 25mm x 50mm often giving better support at plasterboard edges. Fix 5mm No.10 self-tapping screws into the central core of Platinum Waterseal Brick Plugs so no separate hole is made through CV3. The screw must engage safely without passing through the plug or puncturing the membrane behind the batten.

Independent floor-supported frames do not require a set membrane-fixing grid, but enough plugs must hold CV3 reasonably tight around corners, openings and junctions. Compatible proprietary metal lining systems and correctly restrained internal masonry linings may also be used where their loads and ties are designed without uncontrolled penetrations.

Fix plasterboard or other approved lining boards so nails and screws penetrate less than the batten depth. Keep services in front of CV3 and support heavy fittings from predetermined battens or structural fixings. Only exceptional through-fixings should penetrate the membrane, and each requires a designed sealed detail.

Platinum Waterseal Brick Plugs fixing Platinum CV3 to the wall, with fixing centres set to suit the internal finish, typically 600mm vertically and 400mm horizontally for timber battens.

Jointing And Sealing

Platinum CV3 has no flange. Position adjacent sheets edge to edge as a close, accurately aligned butt joint, keeping the cut edges straight and free from gaps, overlaps or distorted studs. Clean and dry the membrane face on both sides of the joint before sealing.

Apply 150mm Platinum Corner Tape centrally over the joint so approximately equal tape width bonds to each sheet. Press it firmly with a hand roller or palm, working progressively along the joint to remove wrinkles, bridging and trapped air while maintaining full contact across both membrane faces.

In cold or damp conditions, dry the HDPE gently with a controlled hot-air gun and warm the butyl only enough to improve tack. Never seal over visible water, dust, mortar, grease or loose contamination. Use continuous tape lengths where practicable, and carefully lap any unavoidable tape ends in accordance with the current tape instructions.

Straight joints may run vertically or horizontally, but unnecessary joints should be avoided and the membrane must remain flat on both sides of every connection. Inspect the complete seal before concealment and repair damaged areas with compatible CV3 and the specified Platinum tape or rope arrangement.

Platinum CV3 butt joint sealed with Platinum Corner Tape (Heavy Duty) during floor installation. 

Wall-To-Floor Junction And AquaTrack Integration

The wall-to-floor junction must transfer water from behind CV3 into AquaTrack without leaving a sealed pocket or unprotected gap. Position the wall membrane and channel upstand to the approved project detail, then clean and dry the surfaces before applying Platinum Corner Tape.

Where CV3 continues across the floor, turn the floor membrane up at the wall and seal it to the wall membrane or AquaTrack upstand with Corner Tape as specified. Form corners neatly and avoid bunching the membrane, blocking drainage openings or pulling the tape across unsupported voids.

If the finished floor build-up extends above the effective AquaTrack upstand, the waterproofing designer must provide a compatible detail that allows condensation from the room-facing surface of CV3 to enter the drainage system without obstructing water from the structural side. Keep the collection route open and use only components confirmed as compatible with the specified system.

Before floor finishes are installed, pour controlled clean water behind the wall membrane and confirm that it enters AquaTrack and reaches the outlet or AquaSump. Rectify slow flow, leakage, trapped sections and unsealed junctions before the system is concealed.

Floor Installation

Provide a suitable outlet and fall or install the designed AquaTrack layout before laying CV3. The concrete base must be clean, stable and free from sharp projections. Where board will lie directly over the membrane, prepare the surface so it does not deviate by more than 5mm beneath a 2m straightedge.

Roll CV3 across the floor with the studs facing down. Cut sheets neatly around the perimeter, channels, columns and unavoidable services without stretching or distorting the studs. The floor membrane must remain loose laid and must never be fixed through to the slab.

Bring adjacent floor sheets together as clean, close butt joints without overlapping the membrane. Centre 150mm Platinum Corner Tape over each joint, press firmly across its full width and check that both edges remain aligned while the seal is formed. The finished floor membrane must remain continuous and free from open edges, wrinkles or trapped debris.

Protect CV3 promptly. Suitable tongue-and-groove board should be loose laid with the floor-finish supplier’s required perimeter expansion gap and staggered, bonded joints. Newton Fibran XPS 500-C or Wykamol High Load may be incorporated where the complete drained floor build-up is compatible and load checked. Alternatively, use at least 50mm reinforced concrete or screed directly over CV3, or at least 65mm where laid over insulation, in accordance with BS 8204-1 and the project specification.

Vaulted Soffit Installation

CV3 may be installed to suitable arched or vaulted ceilings where the construction provides a continuous fall to drainage. Survey the curve, end walls, joints and outlet route before cutting so the membrane can follow the substrate without excessive tension, open folds or areas of sagging that could retain water.

Position the membrane studs towards the soffit and support it with Platinum Brick Plugs Without Seals. Form a continuous ring of Platinum Waterseal Rope around each plug and drive the fixing firmly enough to compress the butyl into a watertight gasket against the curved membrane face. Standard sealing washers should not be used where the curve prevents an even seal.

Where separate sections meet across the vault, form a close butt joint and seal it centrally with 150mm Platinum Corner Tape. Plan shaped cuts carefully and keep the number of joints to a practical minimum. Prevent sagging between fixings so no pocket can hold water or debris.

At each end wall, turn the vault membrane down by at least 200mm. Mitre only as necessary to follow the curve, seal every cut with approved tape or rope, and fit the wall membrane in front of the turned-down ceiling sheet so water continues towards the designed drainage route.

Flat Soffit Restrictions

Flat below-ground soffits should not be lined with CV3. The membrane requires a minimum slope of 10% so any water behind it can move towards the designed drainage point instead of ponding against the sheet, fixings or taped joints.

Where the soffit does not provide this fall, select another waterproofing approach through the project designer. Do not attempt to create drainage by allowing the membrane to hang or by relying on a loose sheet to form channels, because sagging creates uncontrolled pockets and places stress on fixings and joints.

Arched, vaulted or suitably sloping soffits must still be checked across their complete width and length. Local depressions, ribs, beams, abutments and changes of direction can interrupt the fall even when the general geometry appears adequate. Resolve those details before installation and ensure every cavity terminates at a safe collection route.

Door Reveals, Corners And Junction Details

Run CV3 continuously around internal and external corners where the sheet can be folded neatly without excessive distortion. Form a square crease and fix the membrane tightly into the angle so the final lining remains straight and the cavity does not bridge across the corner.

If the sheet becomes misshapen around a return, stop at the corner and begin a new piece rather than forcing a distorted fold. Butt the adjoining edges closely and seal them with 150mm Platinum Corner Tape. Use Waterseal Rope where a shaped three-dimensional detail cannot make full contact with flat tape.

Where possible, install CV3 across window openings and cut it away afterwards so the main sheet remains continuous. Seal the exposed perimeter using the correct combination of Platinum Joint Sealing Membrane Tape, Waterseal Rope and Corner Tape. At doors or fixed obstacles where this method is impossible, bring the membrane accurately to the perimeter and seal the gap with the same care.

Coordinate thresholds with AquaTrack Floor Drain, perimeter channel or another approved continuity detail before fixing. Avoid isolated cavities beside frames and never leave an unsealed reveal or return where water can bypass the membrane and reach the dry lining.

Protrusions Through Platinum CV3

Avoid services through the membrane wherever practical and route pipes, cables, conduits, sockets and controls on the dry side. Where a penetration is unavoidable, establish its position before cutting and keep the opening as small and regular as possible.

For floor services, trim CV3 closely around the pipe or conduit and fill the remaining gap completely with Platinum Waterseal Rope. Where necessary, add a compatible CV3 patch, seal it to the service with rope and seal its outer edge with Platinum Joint Sealing Membrane Tape or Corner Tape.

Use suitable proprietary collars or sleeves for larger, grouped, moving, hot or irregular services where a simple rope-and-patch detail cannot provide durable continuity. The service material, temperature, expected movement and future replacement method must be compatible with the selected seal.

Exceptional structural fixings through a lined wall require a predetermined load-bearing and waterproofing detail. Fix heavy objects into designed battens or structural supports wherever possible. Any hole through CV3 must be packed and sealed with compatible flexible butyl products before it is concealed.

Protection Of Platinum CV3 After Installation

Protect CV3 from sharp tools, dropped fixings, masonry fragments, wheelbarrows, ladders and concentrated foot traffic as soon as each area is complete. A concealed tear, displaced seal or crushed drainage path can compromise the finished system even when the flat face still appears largely intact.

Keep ultraviolet light, high temperatures, open flame and incompatible chemicals away from exposed rolls and installed sheets. Do not leave CV3 uncovered longer than necessary, and prevent wet trades from dropping mortar, screed or plaster into the cavity, AquaTrack channel or inspection ports.

Coordinate all subsequent work through one responsible person. Electricians, plumbers, joiners, dry liners and floor installers must understand that they cannot drill, nail or screw through the membrane without an approved sealed detail. Mark restricted fixing zones and provide predetermined battens or service routes before finishes are closed.

Where temporary protection board is used, ensure it does not crush the studs or block drainage. Remove protective materials carefully, inspect the complete membrane and clean the channels immediately before applying permanent floor or wall protection.

Ventilation And Humidity Control

CV3 has very high resistance to vapour diffusion. When positioned on the cold side of insulation, it can increase interstitial-condensation risk unless the wall or floor build-up and internal environment are designed properly. Carry out the appropriate BS 5250:2021 assessment and consider a vapour-control layer on the warm side where required.

Habitable basements and Grade 3 spaces normally need planned mechanical ventilation, background heating or another specialist environmental-control strategy. The required air-change rate, extract location, make-up air, noise, energy use and control method must be designed for the room’s occupancy and moisture generation.

Do not open the membrane cavity directly to the room as an improvised condensation measure. A below-ground system should remain controlled because unrestricted openings may allow odours, vermin, moisture movement or water to bypass the intended drainage and protection details.

Monitor relative humidity after completion and address persistent internal sources such as wet construction materials, clothes drying, unvented appliances or inadequate extraction. Structural waterproofing controls water from the ground; it does not replace normal management of indoor moisture and air quality.

Inspection Before Finishes

Inspect the full CV3 installation before dry lining, flooring, concrete or screed conceals it. Confirm that the membrane is correctly orientated, tight to walls and vaults, studs are not crushed, every fixing is sealed and no tears, open edges, wrinkles or unsupported joints remain.

Check every butt joint, corner, window and door detail, service penetration, wall-to-floor transition and AquaTrack connection. Confirm that 150mm Platinum Corner Tape remains centred over each sheet joint, then roll it firmly and replace any section contaminated by dust, water, oil or loose debris rather than attempting to press it back into service.

Vacuum cavity edges and drainage channels. Flush AquaTrack and Floor Drain Channel with clean water and verify free movement to the outlet or AquaSump. Operate pumps, high-water alarms and any back-up system, and check that discharge cannot return towards the structure.

Photograph the finished membrane, channels, outlets, sump, pipework and all concealed details. Record dimensions from permanent reference points and complete the installer’s inspection documentation. Do not approve concealment until defects are repaired and the system performs as intended.

Repairs To Platinum CV3

Repair damage before it is concealed. Clean and dry the affected CV3 thoroughly, trim ragged material where necessary and assess whether the studs and cavity remain serviceable. A small clean puncture may be repaired with the approved Platinum tape detail, while a larger tear requires a compatible patch extending well beyond sound membrane on every side.

Use Platinum Waterseal Rope around irregular holes, plug penetrations or three-dimensional details, then secure the repair with Joint Sealing Membrane Tape or Corner Tape as appropriate. Apply firm pressure across the complete seal and use controlled warmth only if needed to remove surface moisture or improve butyl tack.

Where damage has crushed a significant area of studs, affected a critical joint, or occurred beside a channel, penetration or wall-to-floor junction, replace the membrane section or obtain a project-specific repair detail. A flat patch that seals the face but blocks the drainage cavity is not acceptable.

After repair, repeat the relevant inspection and controlled water test. Photograph the completed work and add it to the waterproofing record so later owners and contractors understand the location and method of the concealed repair.

Maintenance And Future Alterations

The protected CV3 sheet itself does not require routine maintenance under normal service conditions. The drainage system that makes Type C waterproofing function does. AquaTrack, Floor Drain Channel, inspection ports, outlets, AquaSump chambers, pumps, alarms, back-up power and discharge pipework must remain accessible and be inspected and serviced at the intervals set by the system designer and equipment manufacturers.

Flush drainage channels through the provided access points and remove lime, silt or debris before it restricts flow. Test pumps and float switches, clean sump chambers, operate alarms and confirm back-up systems under controlled conditions. Keep written service records and investigate changes in pump frequency, unusual noise, odour, dampness or water level promptly.

Future shelving, cupboards, skirtings, flooring, services and wall-mounted equipment must not be fixed through CV3 casually. Use recorded battens and designed support points, or obtain a waterproofing detail for each new penetration. Even a small unsealed fixing can provide a route for water to bypass the system.

Provide the owner with drawings, photographs, product information, test records, access-point locations, pump manuals and maintenance contacts. Any contractor altering the space should review this information before drilling, lifting floors or opening linings.

Key Limitations

• CV3 is a cavity drain membrane and is not resistant to hydrostatic pressure as a standalone barrier; it requires a complete designed drainage and discharge system.

• The shallow 3mm cavity must remain clean and unobstructed, making control of drilling dust, mortar, lime deposits, silt and crushed studs particularly important.

• CV3 can contribute to a Grade 3 internal environment only as part of a coordinated system with suitable drainage, resilience, ventilation, inspection and maintenance.

• Hazardous chemicals, unknown industrial residues, active structural movement and unstable substrates require specialist investigation and project-specific assessment before they are concealed.

• Flat retaining soffits are unsuitable. Vaulted, arched or sloping soffits require a dependable fall and sufficient separately sealed fixings to prevent sagging and ponding.

• Floor membrane must never be punctured by fixings. Screed, board, Newton Fibran and Wykamol High Load build-ups require appropriate support, drainage and load checking.

• Very high vapour resistance can increase condensation risk when CV3 lies on the cold side of insulation; ventilation, heating and BS 5250 assessment remain essential.

• CV3 must be protected from fire, impact, ultraviolet exposure, high temperatures and uncontrolled penetrations by later trades throughout installation and service.

• CV3 sheet-to-sheet joints must be formed as close butt joints and sealed centrally with 150mm Platinum Corner Tape; do not overlap adjoining sheets.

• Pumps, alarms, battery back-up and telemetry do not eliminate risk. Their capacity, power provision, discharge and service regime must match the consequences of failure.

Storage And Shelf Life

Store CV3 rolls upright in their original protective wrapping, under cover and away from sharp objects, direct sunlight, high temperatures and open flame. Do not stack or position rolls where they may be crushed, distorted or punctured by other materials.

Keep Platinum tapes, Waterseal Rope, plug seals and other butyl products clean, dry and within the temperature conditions stated on their packaging. Protect AquaTrack components from impact and deformation, and store cementitious products, biocides and Anti-Lime Sealer according to their separate labels and safety information.

Published CV3 data states a service life equal to the structure for correctly installed and protected membrane rather than a finite shelf life for the wrapped roll. Inspect all stored materials before use and reject membrane with brittle areas, damaged studs, contamination or prolonged uncontrolled exposure.

Other Technical Information

Platinum CV3 is recyclable polyethylene, subject to clean recovery and suitable recycling facilities being available at the time of removal. Offcuts contaminated with butyl tape, mortar, hazardous substrate material or other site waste must be handled through the appropriate waste stream.

Platinum CV3 is available in clear 2m x 10m and 2m x 20m rolls, providing nominal areas of 20m² and 40m². Actual project coverage must allow for cuts, corners, reveals, openings, junctions, service details, repairs and reasonable wastage.

Technical values describe laboratory or declared product performance and do not determine the suitability of a complete wall or floor. Structural loading, insulation, screed reinforcement, fire performance, condensation, drainage capacity, groundwater, penetrations and final occupancy require separate project-specific assessment.

Use the latest applicable Platinum CV3 Declaration of Performance and instructions for every system component. Installation must also follow the project-specific waterproofing design and any applicable Building Control or structural-warranty requirements. Where site conditions fall outside the published scope, obtain project-specific advice from Platinum Chemicals and the waterproofing designer before work begins.

Q) What is Platinum CV3 Waterproof Membrane?

A) Platinum CV3 Waterproof Membrane is a high-density polyethylene cavity-drain sheet with a compact 3mm studded profile. It is designed for internal waterproofing on suitable walls, floors, vaults and tunnels, particularly in basements and other earth-retaining structures. The studs hold the membrane away from the substrate, creating a shallow air and depressurisation gap that separates the internal finish from damp, salts and water-bearing masonry. Water entering the structure can move through this cavity towards a compatible drainage and discharge system. Platinum CV3 is a non-meshed membrane, so it is normally protected by dry lining, battens, an independent frame, internal masonry or a compatible load-spreading floor construction rather than receiving plaster or render directly.

Q) How does Platinum CV3 work as a cavity-drain membrane?

A) Platinum CV3 manages water after it enters the building structure rather than attempting to resist all hydrostatic pressure at the internal surface. Its 3mm studs create a continuous cavity behind walls or beneath floors. Water can travel through this space towards a compatible perimeter drainage channel, gravity outlet or correctly specified sump-and-pump system. The smooth internal face remains separated from damp and salt-contaminated masonry, helping protect boards, flooring and decorative finishes. This method is known as Type C drained protection. Reliable performance depends on the complete system, including sealed butt joints, watertight fixing points, correctly detailed corners and penetrations, unobstructed drainage, sufficient discharge capacity, accessible inspection points and planned maintenance throughout the waterproofed area’s working life.

Q) Why does Platinum CV3 have a 3mm studded profile?

A) The 3mm profile creates a useful drainage cavity while taking up very little internal space. This makes Platinum CV3 particularly valuable around stairs, low ceilings, doorways, narrow passages and floor build-ups where a deeper membrane would reduce headroom or usable room dimensions. It can also help align new floor levels with existing thresholds during refurbishment. The compact cavity requires careful preparation because loose debris, mortar, drilling dust, silt, limescale or standing water can restrict its drainage capacity more readily than a deeper void. Floor falls, channel connections and discharge routes must therefore be planned and tested thoroughly. CV3 should be selected because its drainage performance, loading capacity and shallow build-up suit the complete project design, not simply because it is thin.

Q) Which roll sizes are available for Platinum CV3 Waterproof Membrane?

A) Platinum CV3 is supplied in 2m-wide rolls measuring either 10m or 20m long, providing nominal gross areas of 20m² and 40m² respectively. The stated coverage is the uncut membrane area and does not include allowances for trimming, corners, reveals, columns, service penetrations, repairs or reasonable waste. Measure every wall, floor, return, opening and vaulted section before ordering, then prepare a sheet layout that minimises unnecessary joints. Standard CV3 has no flat flange, so adjoining sheets normally meet at a butt joint sealed with 150mm Platinum Overtape. Calculate the required quantities of Overtape, Waterseal Brick Plugs, Waterseal Tape, Waterseal Rope, drainage components and finishing materials separately from the gross membrane area.

Q) What are the main advantages of Platinum CV3 Waterproof Membrane?

A) Platinum CV3 combines a shallow 3mm build-up with the flexibility to waterproof suitable walls, floors, vaults and tunnels. Its compact profile preserves valuable headroom and floor area, while the HDPE sheet can be cut, positioned and mechanically fixed relatively quickly. It isolates internal finishes from damp, salts and contaminated substrates without requiring the extensive surface preparation often associated with fully bonded tanking, although loose or unsafe materials must still be removed. The membrane provides strong vapour resistance and is waterproof, salt inhibiting, root resistant and contaminant resistant. It also has no curing period of its own. These benefits depend on correct jointing, compatible protected finishes, effective drainage, competent installation and continued access for maintaining channels, outlets, sumps and pumps.

Q) Where can Platinum CV3 Waterproof Membrane be used?

A) Platinum CV3 can be used in domestic and commercial basements, cellars, underground corridors, storage rooms, plant areas, tunnels, earth-retained walls and correctly detailed vaulted structures. It is especially useful where low ceilings, stairs, narrow spaces or restricted floor levels make an 8mm membrane impractical. CV3 may be installed on suitable walls and floors as part of a coordinated Type C waterproofing system. It can also serve as a damp-proof sheet in an appropriate above-ground specification, provided avoidable moisture sources are corrected first. Every application requires assessment of the structure, groundwater risk, substrate stability, drainage capacity, proposed internal use and finish. Habitable, pumped, complex or high-risk schemes should be designed and installed by competent structural-waterproofing specialists.

Q) Can Platinum CV3 help create a habitable Grade 3 basement?

A) Platinum CV3 can form part of a Type C system designed to provide Grade 3 conditions, where water penetration and dampness are unacceptable, as commonly required for habitable basements. The membrane separates the internal construction from the retaining structure and directs incoming water towards controlled drainage. It cannot provide the required environment independently. The completed result depends on structural condition, anticipated ingress, sealed details, drainage capacity, gravity or pumped discharge, alarms, power resilience, ventilation, insulation, heating, humidity control and maintenance. Current below-ground projects should be designed in accordance with BS 8102:2022. Building Regulations, warranty requirements and the intended room use must also be considered, with a competent waterproofing design specialist coordinating the full construction before installation begins.

Q) Can Platinum CV3 be installed on walls and floors?

A) Platinum CV3 is suitable for both walls and floors, but the installation and protection methods differ. On walls, the studs face the substrate and the membrane is mechanically fixed using sealed Platinum Waterseal Brick Plugs. It may be fitted vertically or horizontally and then protected by an appropriate lining. On floors, CV3 is normally loose-laid with the studs facing down, cut neatly to the room perimeter and connected to the wall membrane and drainage-channel upstand. Adjacent sheets are butt-jointed with 150mm Platinum Overtape. Floor fixings must not puncture the membrane, and the finished construction needs a compatible load-spreading layer. Both applications require sealed transitions, clear drainage paths and protection from tools, debris and later building work.

Q) Which substrates are suitable for Platinum CV3?

A) Platinum CV3 can be installed over stable concrete, brickwork, blockwork, stone, sound render, sound screed and comparable masonry substrates capable of accepting the specified fixings and supporting the intended finish. The background does not need to be cosmetically perfect, but it must not contain projections or loose material that could puncture the sheet or obstruct drainage. Unsound plaster, weak render, defective screed, deep voids and unstable areas should be removed or repaired. Floor bases must be sufficiently flat and capable of directing water towards drainage without isolated low points. Structural movement, collapsing masonry, uncontrolled water flow, hazardous contamination and timber decay require proper assessment and remedial work before concealment. The membrane must never be used to hide an unresolved structural or safety problem.

Q) How should a surface be prepared before installing Platinum CV3?

A) Remove loose plaster, weak render, defective screed, organic matter, rubble and sharp projections. Repair deep holes and severe irregularities with a compatible mortar, then allow all new work to dry thoroughly before fixing the membrane. Sound render may remain if it is stable and will not weaken the fixing points. Brush visible mould or masonry fungal growth from the wall and apply a suitable masonry biocide in accordance with its instructions. Dry rot requires detailed specialist assessment, while affected timber should be repaired or treated before the area is enclosed. Floors must be clean, stable and free from oil, dust and debris. Above ground, correct avoidable moisture sources, including leaking services, defective rainwater goods or an appropriately diagnosed damp-proof-course problem, wherever practical.

Q) How flat must a floor be before Platinum CV3 is installed?

A) New concrete bases should be constructed in accordance with BS 8204-1:2003+A1:2009, which remains the current code of practice for concrete bases and cementitious levelling screeds receiving flooring. For Platinum CV3, the prepared surface should not deviate by more than 5mm beneath a 3000mm straightedge. Unsound screed, ridges, sharp projections, deep hollows and unstable areas must be repaired before installation. Flatness alone is not enough in an earth-retaining application: the floor must also permit water to travel towards the designed channel and discharge point without persistent ponding. Standing water can carry silt or limescale into the shallow cavity and reduce drainage. Check levels and drainage before covering the slab, then correct any low points or reverse falls.

Q) How is Platinum CV3 installed on a wall?

A) Position Platinum CV3 with its studs against the wall and the smooth face towards the room. It can be installed vertically or horizontally; horizontal fitting generally creates fewer joints, while vertical strips are lighter and easier to handle. Align the first sheet using a spirit or laser level. Drill through the centre of a stud near the top edge with a 10mm bit to a depth greater than the fixing, then insert a Platinum Waterseal Brick Plug until its rubber washer seals flush against the membrane. Add another top fixing approximately 2m along and continue setting out while checking the level. Complete the required fixing pattern, form sealed butt joints and inspect corners, penetrations and the drainage termination before installing the protective lining.

Q) Which fixings and centres should be used for Platinum CV3?

A) Platinum Waterseal Brick Plugs are used for standard wall installations. Each plug has a soft rubber sealing washer and is installed through the centre of a membrane stud into a clean 10mm hole. Fixing centres depend on the selected lining. Typical guidance is 600mm vertically by 400mm horizontally for treated timber battens and 800mm vertically by 600mm horizontally for fixed metal-track systems. Barrel vaults require closer restraint, generally about 300mm around the curve and 600mm along its length. Free-standing frames and internal walls do not require a support grid connected to the membrane, but sufficient plugs must keep CV3 neat and reasonably tight. Align all plug rows and add restraint around corners, reveals, edges and irregular surfaces where required.

Q) How are joints sealed in Platinum CV3 Waterproof Membrane?

A) Standard Platinum CV3 has no flat flange, so adjoining sheets normally meet edge to edge as a close butt joint. Clean and dry both membrane faces, then centre 150mm Platinum Overtape over the joint so it bonds evenly to each sheet. Press the entire tape surface firmly with the palm or a suitable roller, removing wrinkles, trapped air and unbonded edges. In cold or damp conditions, a controlled hot-air gun can evaporate light surface moisture and improve adhesion, but the HDPE must not be overheated or distorted. Platinum Waterseal Tape is used for compatible DPC interfaces and specified lapped details rather than as the normal face seal over a CV3 butt joint. Inspect every joint before concealment.

Q) How should corners, returns and door reveals be detailed?

A) Fit Platinum CV3 tightly into internal and external corners without stretching the HDPE, crushing studs or bridging an unsupported void. Form a neat continuous fold where possible. If the wall profile causes the membrane to distort, make a controlled cut and create a new butt joint sealed with Platinum Overtape. Extend the waterproofing onto return walls so damp cannot bypass the treated area and damage adjacent finishes. At a door opening in vaulted work, a separate membrane section may be fitted around the head and lapped approximately 100mm down the sides before the wall sheet wraps into the reveal. Seal angled gaps with Overtape and use a compatible project-specific detail where the studded membrane cannot fit within a narrow junction.

Q) Does Platinum CV3 require a drainage channel or sump?

A) Platinum CV3 must be connected to effective drainage whenever it is used in a full or partly earth-retaining structure. A compatible perimeter channel is normally positioned at the wall-to-floor junction to collect water from behind the wall membrane and from the structural joint. The channel then discharges through a safe gravity route or into a correctly sized sump-and-pump arrangement. Standing water must not remain beneath the membrane because silt and limescale can obstruct the shallow cavity. The system should include accessible jetting or rodding points so channels can be inspected and flushed. Pump duty, chamber capacity, discharge pipework, high-water alarms, standby equipment and backup power should reflect the anticipated inflow and the consequences of drainage or electrical failure.

Q) How is Platinum CV3 installed on a floor?

A) Starting at one side of the room, unroll Platinum CV3 with its studs facing down and cut it accurately to the perimeter, columns, thresholds, sump covers and unavoidable services. Lay the next width so the edges meet as a close butt joint. Clean and dry both faces, apply 150mm Platinum Overtape centrally over the joint and press it firmly across its full width. Seal the floor membrane to the compatible perimeter-channel upstand using the specified Overtape detail while maintaining the intended drainage path. Compatible horizontal DPC connections are sealed with Platinum Waterseal Tape. Do not drive fixings through the floor membrane. Protect completed areas from sharp tools, rubble and concentrated traffic, test drainage and then install the specified load-spreading floor finish.

Q) Can Platinum CV3 be laid over green concrete for faster finishing?

A) Platinum CV3 can form part of a fast-track floor build-up over green concrete once the slab is sufficiently firm to walk on. The membrane creates a dry working surface above while construction moisture remains controlled within the cavity beneath, allowing compatible floor finishes to proceed without waiting for the conventional relative-humidity level normally required for direct application to concrete. This method does not remove the need for adequate structural strength, surface flatness, drainage, load assessment or protection against punctures. The full floor build-up must be designed for the intended use, and every membrane joint and perimeter connection must be sealed. Levelling compounds, adhesives, screeds and other materials used elsewhere remain subject to their own curing, moisture and compatibility requirements.

Q) How should pipes and services passing through Platinum CV3 be sealed?

A) Route pipes, cables, conduits and ducts on the dry side of Platinum CV3 wherever possible, particularly on floors and overhead surfaces where penetrations create significant weaknesses. If a service must pass through the membrane, cut a neat opening with the smallest practical clearance. Seal the gap with a compatible high-quality hybrid polymer adhesive where appropriate. For a more substantial detail, add a CV3 or compatible DPC patch, seal it to the service with compressed Platinum Waterseal Rope and seal the patch perimeter with Platinum Waterseal Tape or the specified compatible tape. The completed detail must accommodate movement, temperature change and future maintenance. Inspect the entire circumference, test where practicable and photograph the penetration before it is covered.

Q) Which wall and floor finishes are compatible with Platinum CV3?

A) Compatible wall finishes include treated timber battens and plasterboard, a free-standing timber or metal dry-lining frame, an appropriate proprietary metal-track system or a properly restrained internal brick or block wall. Timber battens should be at least 25mm x 38mm, although 25mm x 50mm can provide better support at board edges. They can be secured into the hollow cores of Waterseal Brick Plugs using carefully selected 5mm self-tapping screws. Floor finishes require a compatible load-spreading construction that protects the studs and avoids all membrane punctures. Timber floors also need the expansion gap specified by the flooring manufacturer. Every lining must satisfy structural, thermal, fire, acoustic and moisture requirements while keeping drainage access points and sump covers serviceable.

Q) Can plaster or render be applied directly to Platinum CV3?

A) Conventional plaster or render should not be applied directly to Platinum CV3 because it is a smooth, non-meshed HDPE membrane and does not provide the mechanical key required for a wet finish. The membrane should instead be protected by a compatible dry-lining frame, treated battens and boards, proprietary lining system or internal masonry wall. Battens and brackets can use the hollow centres of correctly installed Waterseal Brick Plugs, preventing unnecessary new penetrations through the waterproofing. Plug cores accept approximately 30mm of screw, so the correct screw length must be calculated from the batten thickness. Overlong or over-tightened fasteners may loosen a plug or puncture CV3. Where a direct plastered finish is required, specify an appropriate meshed waterproofing membrane rather than modifying CV3 on site.

Q) Can Platinum CV3 be used on vaulted ceilings and soffits?

A) Platinum CV3 can be installed on correctly detailed vaulted cellar ceilings where sheets, joints and fixings allow water to drain without ponding. The membrane must remain tight to the curve and free from sagging pockets. For overhead work, use Platinum Waterseal Plugs without their rubber washers and form each fixing seal with compressed Platinum Waterseal Rope. Barrel-vault fixing centres should generally be about 300mm around the curve and 600mm along its length, with plug rows aligned for later battens. Flat soffits require a dependable fall towards the designed drainage route and enough restraint to prevent sagging. Vaults, end walls, door heads and overhead penetrations are complex waterproofing details and should be completed by experienced structural-waterproofing installers using an approved project-specific design.

Q) What tools and accessories are needed to install Platinum CV3?

A) Typical tools include an SDS hammer drill, suitable 10mm masonry bits, a wide-headed hammer or mallet, sharp utility knife, tape measure, spirit level, rotating laser, clean lint-free cloths and a roller or firm pressure tool for tapes. A controlled hot-air gun can assist surface drying and tape adhesion in cold conditions, but open flames must never be used. Confirmed system accessories include Platinum Waterseal Brick Plugs, 150mm Platinum Overtape, Platinum Waterseal Tape and Platinum Waterseal Rope. The project may also require compatible perimeter drainage, inspection eyes, outlets, a sump, pumps, alarms, backup equipment, DPC patches, treated battens and protective linings. Provide suitable PPE, lighting, safe access equipment and dust control before installation begins.

Q) Does Platinum CV3 require a curing or drying period?

A) Platinum CV3 itself does not cure because it is a prefabricated HDPE sheet rather than a wet-applied coating. The specified lining or floor construction can normally proceed after the membrane, fixings, butt joints, corners, penetrations and drainage connections have been inspected and tested. Associated materials still need the correct drying or curing time. Repair mortars, screeds, levelling compounds, biocides, adhesives and sealants must reach the condition required by their individual instructions. New wall repairs should be allowed to dry thoroughly before CV3 is fixed. A separately designed fast-track floor arrangement may allow CV3 to be installed over walkable green concrete, but this does not apply automatically to every repair or finish. Clean, dry bonding surfaces remain essential for Overtape, Waterseal Tape and Waterseal Rope.

Q) What are the main technical specifications of Platinum CV3?

A) Platinum CV3 is manufactured from HDPE with a membrane thickness of 0.6mm, stud depth of 3mm and density of 500g/m². Its service-temperature range is -50°C to +80°C, with a softening temperature of 126°C. Tensile strength is 418N in the machine direction and 488N in the cross direction under BS 12311-2. Water-vapour resistance exceeds 3020MNs/g, and resistance to static loading is greater than 20kg under BS 12730. The membrane passes watertightness testing at 60kPa for 24 hours to EN 1928, has a declared compressive strength of 250kN and carries a Class E reaction-to-fire classification. Project loading and drainage capacity still require specific assessment.

Q) Which standards and product declarations apply to Platinum CV3?

A) Platinum CV3 is declared as a Type V damp-proof sheet in accordance with BS EN 13967:2012+A1:2017. Its declared performance includes a watertightness pass at 60kPa for 24 hours to EN 1928, Class E reaction to fire under EN 13501-1 and compressive strength of 250kN under BS EN ISO 25619-2. Below-ground Type C systems incorporating CV3 should be designed in accordance with BS 8102:2022, including assessment of groundwater, structure, drainage, discharge, maintainability and intended internal conditions. Concrete bases and cementitious levelling screeds should follow BS 8204-1:2003+A1:2009. Compliance depends on the complete project design and installation, not the membrane sheet alone, so compatible details and system components must be coordinated by competent specialists.

Q) What guarantee is provided with Platinum CV3 Waterproof Membrane?

A) Platinum CV3 is guaranteed against deterioration for 30 years when it is correctly specified, installed and protected in accordance with the applicable requirements. Long-term waterproofing performance also depends on the surrounding system. Butt joints, fixing seals, wall-to-floor transitions and penetrations must remain intact, while drainage channels, outlets, sumps, pumps and alarms must continue to operate. The membrane should remain covered by an appropriate wall or floor finish and protected from ultraviolet light, sharp objects, impact, excessive heat and open flames. Later contractors must not drill or screw through concealed areas. Retain product records, installation drawings, photographs and maintenance information so the waterproofing arrangement can be protected and serviced throughout the building’s use.

Q) What maintenance does a Platinum CV3 waterproofing system require?

A) The protected CV3 membrane normally needs little direct routine attention, but every connected drainage and pumping component must remain accessible and serviceable. Inspect and flush perimeter channels through suitable jetting or rodding eyes so silt, limescale and debris cannot restrict the shallow drainage route. Sumps should be cleaned, pumps and floats operated, non-return valves checked and discharge pipework examined in accordance with the system design and equipment instructions. Test high-water alarms, standby pumps and backup power where installed. Maintenance frequency should reflect groundwater risk, water flow, lime exposure, pump activity, occupancy and any guarantee requirements. Keep as-built drawings, photographs, access locations and no-fix zones available so future work does not puncture the membrane or conceal maintainable equipment.

Q) What are the main limitations of Platinum CV3 Waterproof Membrane?

A) Platinum CV3 is not a stand-alone barrier capable of resisting hydrostatic pressure without functioning drainage and safe discharge. Its shallow 3mm cavity can be obstructed by debris, silt, limescale or standing water if floor falls and maintenance are inadequate. Standard CV3 is non-meshed, so direct plaster or render is unsuitable. Overtape and other seals require clean, dry surfaces, while all floor penetrations should be avoided wherever possible. Flat soffits need a dependable fall and close support to prevent ponding. The membrane cannot correct structural instability, uncontrolled leaks, dry rot, hazardous contamination or avoidable building defects. It must also be protected from ultraviolet exposure, impact, excessive heat, flames and later drilling, nailing or screwing by follow-on trades.

Q) What practical tips help ensure a reliable Platinum CV3 installation?

A) Plan the sheet orientation, plug rows, butt joints, wall-to-floor connection, drainage route, sump, services and final finishes before cutting. Measure gross areas separately from waste and calculate Overtape, Waterseal Plugs, Waterseal Tape and Waterseal Rope from the actual layout. Keep the shallow cavity free from drilling dust, mortar and rubble, and use a spirit or laser level frequently so long sheets do not drift or kink around corners. Clean and dry every taped surface, centre 150mm Overtape accurately and consolidate it firmly across its full width. Before concealment, inspect membrane, fixings, joints and penetrations, flush drainage, test pumps and alarms, photograph critical details, mark no-fix zones and provide the owner with a maintenance schedule.

Technical Data Sheet

Declaration of Performance (DoP)