Platon P8 - Basement Tanking Membrane (8mm Stud)

Platon P8 - Basement Tanking Membrane (8mm Stud)

Isola | Basement Waterproof Membranes

Platon P8 is a BBA Approved, 8mm Stud, Basement Waterproof Tanking Membrane.

Platon P8 is used as a waterproofing drainage layer applied to the inside face of basement and below ground walls and floors within a drained cavity membrane system. Platon P8 is manufactured from High Density Polyethylene and is impermeable to water, water vapour or Radon gas.

  Platon P8 is supported by BBA Certification Certificate Number 01/3823.

Available in various Roll sizes ranging from 10M² to 40M².


Platon P8 Cavity Drain Membrane

Platon P8 Cavity Drain Membrane is manufactured from high-density polyethylene (HDPE) for use within System Platon, Isola's internally applied Waterproofing System that includes the Aqua Channel Drainage System and Aqua Pumping Systems.

Platon P8 impermeable and resistant to the usual chemicals in the building construction. Studs are formed in a regular pattern on the one face of the product. The studs are spaced at approx. 25mm centres in both directions.

Platon P8 is CE marked in accordance with EN 13967 and EN 13984. A separate declaration gives values for several characteristics.

Platon P8 membrane is tough but pliable and can be bent round corners and projections without risk of breaking, even in very low temperatures. The product can be easily cut with a knife or scissors.

Technical Data:

Membrane Material HDPE
Sheet Thickness Nominal 0.50mm
Stud Height Approx. 6.5mm
Construction Height Approx. 7mm
Unit Weight 0.45kg/m²
Deformation Under Long Term Loading Max. 20% (at 50 kN/m²)
Compressive Strength 150 kN/m²
Working Temperature -10° to +60°C
Softening Temperature +160°C
Linear Coefficient of Thermal Expansion 0.18mm/m.°C
Water Vapour Resistance 280m equivalent air layer
Air Gap Volume 4.0L/m²
Drainage Capacity Approx. 3.8L/m²
No. of Studs (Approx) 1640 per m²
Life Expectancy At Least 50 Years for Defined Applications
Colour Natural

Platon P8 is CE marked in accordance with EN 13967 and EN 13984. A separate declaration gives values for several characteristics.

Associated Products:

  • Platon Brick Plugs & Seals: For Fixing the Membrane to the substrate.

  • Platon Sealing Tape: Provides a double-sided waterproof seal when joining Membranes along the flange where they overlap.

  • Platon Sealing Rope: Used to form a seal around the neck of the Platon Brick Plug if not using Sealing Washers

  • Platon Corner Strip: Used to link Waterproof Membranes at Floor to Wall joints.

  • Platinum Lime Inhibitor: Used for the control of primary and secondary efflorescence in concrete mixes. Should be applied to concrete surfaces prior to the installation of a 'Type C' Cavity Drain Membrane System to prevent the ‘leaching’ of free lime from the concrete.

  • Platon Aqua Channel System: A PVC drainage conduit which should be fitted around the periphery of an internal floor at the vulnerable wall / floor junction. Any water entering the building through walls or curved soffits is controlled behind the membrane and enters the channel through before being diverted to the mechanical (Sump and Pump) or natural drainage point.

  • Platon Aqua Pump System: A ready to use complete water control system principally designed for use in below ground structures to control water ingress.

Design Consideration

Membrane Suitability:

Platon Cavity Drain Membrane can be applied to almost all sound building structures below ground, which are affected by dampness or water ingress. However, they are not recommended for installation in the following situations.

  • Where the Cavity Membrane System cannot be drained, otherwise the system will fail.

  • Fixed onto internal flat soffits unless the soffit has an existing fall or a fall can be formed at the design stage (in the case of new build construction) or created using sand & cement renders, otherwise water would pond behind the membrane and build up like a balloon. The weight of water would inevitably burst the membrane seals, which are not designed to hold water under pressure.

  • Under or on top of concrete/stone staircase treads and risers, because of the many convoluting junctions and angle details. In such circumstances, we recommend they be treated independently using an epoxy vapour barrier.

Ingressing Water:

Platon Cavity Drain Membranes are capable of dealing with (quite) large volumes of water, so ingressing water will not usually require remedial action. But if the flow rate is such that it will be able to carry silts/dissolved lime with it, then this inflow should be stemmed/controlled prior to fitting the membrane. This can be achieved as follows.

  • If ingressing water is localised then the application of Platinum Aqua Stop Plugging Compound will often be sufficient.

  • If ingressing water is more general and cannot be dealt with by localised plugging, consideration should be given to applying a general coat of 3:1 render incorporating an accelerator in the mix.

When water is flowing through concrete or mortar (particularly when it is new) there is a tendency for dissolved lime to be brought into the cavity.

This lime can then come out of solution and block up cavities and drains. If this is a risk, then the source of water ingress needs to be treated in the same way as silt bearing water, as described above.

NB: Regardless of conditions at the time of inspection, BS 8102 says it must be assumed hydrostatic pressure is going to occur at some time during the lifetime of the basement. This means that some form of water removal system must always be fitted with a Platon Cavity Membrane in below ground structures.

Drainage Types:

There are two principle forms of drainage, these are natural (gravity) and mechanical (sump & pump) and can be used in conjunction with falls or drainage channels.

However, when assessing the type of drainage facility to be used and because the drainage is the key to the success of the cavity membrane system, it is important to take into consideration the following points.

Natural - (Combined Foul Chambers & Integral Gullies)

Where drainage with gravity is feasible within the bounds of the property or at a point of exit from the property, it is most important to establish that the ‘internal drainage’ is in good working order and to question whether the local drains are connected to public drains or a soakaway.

Drains can and do block up or back up causing flooding, including escape of foul waste and pungent smells.

Soakaways can also fill up during periods of heavy rain, which would lead to flooding and failure of the cavity membrane system.

In situations where the Platon membrane installer finds that the only possibility of draining the cavity membrane is into a foul / soakaway system or his client so instructs, liability for the waterproofing system should therefore be excluded in the event of blockage of the foul pipes or the soakaways filling up. We, and the products Manufacturer, always recommend the inclusion of sump and pumps.

Mechanical - (Sump & Pump)

Platinum Chemicals offer an off-the-shelf sump and pump drainage system, The Aqua Pump Range and ‘Aqua Pump Pro Range’ which has been specifically  designed for the purpose of controlling ground water ingress.

The simple to fit sump pump kit comprises a polyethylene pre-formed sump chamber with a structural lid. The submersible Aqua Pump is controlled by an automatic integral float switch and comes with a non-return valve and a high level water alarm that warns of mechanical or power failure.

However, it would be prudent to install a double pump system ‘The Aqua Pump Plus Kit’ which consists of two pumps in the sump chamber. This secondary pump would provide a back up in case of mechanical failure of the principal pump.

Consideration should also be given to installing a Battery Back-up Pump in case of a power failure and is also available from Platinum Chemicals.

Drainage Channel - (Platon Aqua Channel Drainage System)

Platinum Chemicals also offer Platon Aqua Channel, which is a PVC drainage conduit specifically designed for the control of water ingress in below ground situations.

It is fitted around the perimeter of the floor at the vulnerable wall / floor junction and can be used in most waterproofing situations, and is particularly suited for use in conjunction with Platon Cavity Drain Membrane Systems.

Water entering the building through the walls is controlled behind the Platon Membrane and diverted to the Aqua Channel at the base of the wall. The water enters the Aqua Channel through pre-drilled drainage holes and must then be diverted to a suitable drainage point, either natural or a sump and mechanical pump. Rodding Eyes can also be incorporated into the Aqua Channel.

Falls - (Floors)

It is essential that there are no undulating surfaces or depressions in the floor. In new build or whenever floors are being replaced, the floor slabs can be designed and constructed to falls 2º or 3º towards the water collection facility, i.e. sump chamber.

Where an existing solid floor is to be retained a sand/cement screed can be laid over the entire floor gently sloping towards the sump. In all cases the floor should always be tested by spraying with a hose, to ensure that all water finds its way to the water collection point before laying the cavity membrane.

Note: Wherever possible (head height permitting) we recommend that Platinum CV20 be used on floors. This is because the CV20 Membrane has a far greater drainage capacity and significantly reduces the risk of hydrostatic pressure building up within the cavity.

Undermining Structures:

Sump Chambers

Consideration must be given to the implications of fitting sumps in the ground, e.g. where unstable elements are present, such as chalk or sand.

The installation of a perforated sump chamber could cause washing away and potential undermining. Therefore, in such cases, only sealed sumps should be installed and structurally held in place by concrete etc, with the water collection limited to that entering from the drainage channels.

The final decision on the sump type in cases where ground conditions are unknown should be delayed until excavation is undertaken.

IMPORTANT NOTE: If there is any concern as to whether there is a risk of de watering the ground to a condition whereby the structure as a whole could or may be undermined, then advice should be sought from a chartered engineer.

Drainage Channel

If the Aqua Channel cannot be formed / inserted into the floor at the wall/floor junction, because there are in-situ reinforcing bars in the slab.

Then either a fall must be created in the floor (as previously described under the heading falls) or a series of small surface channels (cut into the floor like chevrons) must be formed with a fall towards the direction of the sump/water collection chamber.

Existing Plasters

Plaster that may be affected by being closed in behind the Platon Cavity Membrane, such as gypsum or lightweight plaster, or where the existing plaster is loose or de-bonding, should be removed from walls / soffits prior to membrane application.

Only where dense and well adhered sand and cement renders are present and where removal may cause unwanted structural damage to substrates can they be left in place.



One of the benefits of using cavity drain membrane is that in general, very little preparation to the substrates is required and although the cavity membrane is flexible and does not need a perfect surface for application, the following points need to be considered.

  • Unsound materials on the surface like renders or plasters need to be removed. Any organic materials such as wallpaper, timber skirtings, fixing grounds etc need to be removed.

  • A specialist Timber Treatment contractor should investigate any fungal decay / infestations in timbers. Also timber that is in contact with damp masonry should be removed or physically isolated.

  • Excessively uneven wall and floor surfaces should be dubbed out/levelled especially if timber battens are to be fixed to support dry lining board. Where a wooden floor finish is required such as T&G flooring grade chipboard, it must also be borne in mind that the membrane will follow the contours of the floor. Therefore to achieve a flat surface, any depressions or undulations must be ironed out to avoid undue movement in the floor finishes.

  • Substrates must be free of sharp protruding objects and debris etc that can damage the membrane. We would also recommend that where mould, mosses, lichens and algae has affected substrates, a surface sterilisation with TRISOL 23 should be used.

  • Loose, friable or defective masonry should be repaired to ensure a solid fixing.

  • New concrete should be treated with Platinum Lime Inhibitor which prevents free lime from the curing concrete being drawn out by ingressing water.

Internal Basement Structures:

Set out below is a generic method of installation, which can be used to apply Platon Cavity Drain Membranes continuously between wall and floor.

NB it is assumed by this stage, that the site and Design Considerations have been assessed and the type of drainage facility chosen has been tested.

Wall Applications:

The installation of Platon P8 Membrane can be fixed to walls either vertically or horizontally, but when choosing the method of application, consideration should be given to the height of walls in relation to the size of the roll of membrane.

There are fewer joints in horizontal applications but it can be awkward and difficult to manoeuvre the weight of a full roll of membrane. Particularly in situations where the membrane has to be taken in and out of numerous recesses, also around convoluting junctions or were walls are not square.

Vertical application may have more joints and require more Platon Sealing Tape, but this method is more manageable and much easier to fix.

Platon P8 Membrane is fixed to walls with a suitable Watertight Brick Plug Fixing, such as Platon Brick Plugs & Seals or Platon Brick Plugs wrapped with Platon Sealing Rope. This will form a seal with the membrane when the plug is driven home into the substrate.

If the ceiling height is constant, measure and cut drops of the membrane to completely cover the wall areas to be treated. Place the membrane against the wall as level as possible by eye sight and in the top right or left hand corner (depending on which way around the room the membrane is being taken) drill a hole through the centre of the membrane stud using a 10mm drill bit.

Insert the brick plug and hammer home the plug till it finishes flush with the membrane.

Using a spirit level, level out the membrane and then drill and fix another Brick Plug in the same manner approximately 1.5M along the top of the sheet and along the same line of stud as the first fixing.

Offer up the next length of membrane and position the flange over the studs of the first sheet and fix with two Brick Plugs at high level as previously described.

Continue on in this manner, ensuring the membrane stays as level as possible until all the walls are covered. These independent membrane drops will relax after a while and hang flatter to the wall. The drops are now ready for the next step.

Thoroughly clean the flange and the studs where the seal is to be made, (the best cleaning material is Paper Towel). Any dust or dirt will compromise the integrity of the sealed joint. If the membrane is covered in plaster or brick dust, wash off with clean fresh water only and allow to dry. DO NOT use soap or detergents, as these will leave traces on the membrane, which may affect the seal at a later date or make sealing more difficult.

The separate membrane drops should now be sealed together using Platon Sealing Tape. Apply the tape to the stud area below, which the flange will cover and press home onto the area between the studs.

Flick over the flange section to cover the tape line, and check for uniformity of cover on tape line. Remove the tape backing paper, starting from the middle section of the wall drop, forming two backing paper tags, one going up and the other down.

On the exposed section of tape apply hand pressure only to the flange to form an initial seal. Carry on to form the seal from the centre section of membrane working up to the top, then go back to the centre and repeat the operation going downwards.

Sealing in this manner will prevent any buckling between the membrane or stress concentration at the joint. In very cold or humid conditions a hot air gun can be used to obtain a good sealed joint.

Now that the membrane is sealed to form one continuous sheet, Brick Plugs can now be fixed through the membrane in position to accommodate the chosen dry lining system.

NOTE: Although a 10mm Drill Bit is the correct size to use, in very soft brickwork this can result in loose fixing. In these circumstances, it is useful to have on hand drill sizes down to 8mm Drill Bit and experiment with different sizes for the best results.

Floor Applications:

Begin at one side of the room and unroll the Floor Membrane against the Wall Membrane with the studs facing down onto the floor.

Allow for the membrane flange overlap, cut the membrane to the desired length or width of the floor. Repeat this exercise until all the lengths / widths required to cover the floor area have been cut.

Roll out the next length/sheet of membrane and position the flange over the studs of the first sheet laid and thoroughly clean the flange and the studs where the seal is to be made as previously described for wall application.

Apply Platon Sealing Tape to the stud area below which the flange will cover and press home onto the area between the studs.

Flick over the flange section to cover the tape line, and check for uniformity of cover on tape line. Remove the tape backing paper, starting from the middle section of the membrane sheet, and peel off backing paper in opposite directions along the flange. On the exposed section of tape apply hand pressure only to the flange to form an initial seal. Carry on forming the seal working away from the centre of the membrane.

Foot pressure can be applied by sliding the sole of the foot over the membrane joint, to ensure that the membranes are fully bonded. Sealing in this manner will prevent any buckling between the membrane or stress concentration at the joint.

In very cold or humid conditions a hot air gun can be used to obtain a good sealed joint.

The next stage of the operation is to link the floor membrane to the wall membrane, which can be achieved, using Platon Corner Strip. Using the Corner Strip, work out how many linear metres there are around the walls, the Corner Strip is supplied in manageable 10M Lengths. Alternatively, our Platinum Corner Tape can also be used.

The Corner Tape is folded in half along the length of the piece to be used and positioned with the crease into the angle as described for the wall / floor junction.

Once correctly aligned, carefully pull off the backing paper and press firmly out with the palm of the hand onto the floor and wall membranes.

Flat Soffit Application:

Platon P8 should not be fixed to the under side of a flat soffit unless a fall exists or a fall can be created in the soffit itself.

The soffit should first be measured to establish the desired lengths or widths of membrane required to cover the area and then a further 200mm of membrane should be added to the measurements, to allow for the membrane to be lapped down all the peripheral walls.

Apply Platon Sealing Rope to Platon Brick Plugs, then around the perimeter edges of the membrane, fold the membrane inward 200mm to form a positive creased and create a down lap. Offer the membrane up to the soffit and position the down lap creases into the junction between the soffit and wall.

Drill and fix enough Brick Plugs through the membrane and into the soffit to hold the membrane in place with the studs against the soffit.

NB: Wherever the soffit membrane meets the wall, a 200mm down lap must be allowed and formed as above.

Offer the next length/sheet of membrane up to the soffit and position the flange over the studs of the first sheet, fix and secure the membrane as described above. Repeat this operation until all the membrane sheets are held in place.

Thoroughly clean the flange and the studs where the seal is to be made as previously described for wall application.

Apply Platon Sealing Tape to the stud area, which the flange will cover and press home onto the area between the studs. The membrane should now be sealed to form one continuous sheet, Brick Plugs can now be fixed through the membrane, in positions to accommodate the chosen dry lining system.

NOTE: It is important to ensure that the membrane is taut against the soffit and doesn’t sag, otherwise water ponding will occur and the membrane/seals could fail.

Internal and external corners are formed in exactly the same way as that which has been previously described in ‘Floor Applications' using Platon P8 with membrane upstand except in this case, they will be formed in reverse and be upside down.

Service Entry Seals:

Where there are services such as pipes, ducting or steel stanchion that protrude through walls or floors, the membrane should be carefully cut and trimmed around the obstacle and sealed using a combination of Platon Sealing Rope and Platon Corner Strip.

Doors and Windows:

Door and Window Frames and timber surrounds should always be removed to enable the Platon Membrane to be extended around or into door and window reveals to maintain the continuity of the waterproofing system and to also provide a physical barrier between the frames and damp masonry.

In situations where the Platon Membrane would restrict or limit the profile of replaced frames, then Plain Damp Proof Course (DPC) can be used to line and protect the reveals instead.

Ventilation - Part F of Building Regulations:

There is no requirement to ventilate the membrane cavity in a fully sealed system such as in under pavement vault application.

In a semi sealed system, the cavity between membrane and substrate can be vented into the room space with passive vents or if this is not possible, it can be vented through the external wall using a 150 x 225 air brick inserted every 1.5M to 2.0M along the wall.

It is important that the cavity between the membrane and internal finish i.e. dry lining is not vented so as to avoid possible interstitial condensation. However, consideration should be given to the risk of condensation forming within the room itself and the introduction of a humidistat controlled extract fan should therefore be recommended.

Refer to BS8102 (2009) Table 2 for further reference. Part F of Building Regulations concerning ventilation in basements.


Wall Finishes:

If timber battens are to be used, the traditional method is to fix a vertical batten 25mm x 50mm.

The Brick Plugs in this instance should be fixed at 400mm centres horizontally and 600mm centres vertically. Platon Brick Plugs will take 25mm of screw, so be sure to purchase the correct length for the thickness of batten.

NB: We would however, recommend that foil back plasterboard be used to prevent interstitial condensation forming in the cavity.

For a metal fast track dry lining system such as Gypliner or Lafarge, the brick plugs should be fixed at 600mm centres horizontally and 800mm centres vertically. If an independent timber or metal frame system is to be used, the wall membrane can be ‘curtain hung’. The membrane is simply dressed down the walls just like hanging a curtain or sheet. This method of installation requires less fixings.

NOTE: We would however, recommend that foil back plasterboard be used to prevent interstitial condensation forming in the cavity.

Floor Finishes:

There is a wide choice of floor coverings that can be laid on top of Platon floor membranes

Platon P8 (Wood Based Flooring) Flooring Grade T & G Chipboard, Parquet, Laminate, Wood Strip
Platon P8 (Sand / Cement Screeds)

Domestic: Minimum 50mm screed or 20mm reinforced polymer modified self-levelling screed.

Industrial: Minimum 75mm reinforced screed or 35mm reinforced polymer modified self-levelling screed.


For Platon Membrane applied to walls at or above ground level, the maximum insulation thickness should be 50mm.

When Platon membrane is applied to earth retaining walls full height of a basement, there is no upper limit to insulation thickness. However, if Platon Membrane is applied to part earth retaining walls, then the maximum insulation thickness should be 50mm.

There is no upper limit to insulation thickness for Platon Membrane applied to solid floors at ground or below ground level.

Curved Soffits and Vaulted Rooms:

When working in a conventional vault with rounded ceilings the water can run off freely and the following method should be adopted:

When lining vaults always work from the front to the back, starting on the centre line of the vault. Measure the length of the vault and add 400mm to this measurement, then cut the membrane to the length.

Form a 900 downturn crease 200mm in from either end of the membrane and prepare the Platon Brick Plugs by wrapping with Platon Sealing Rope.

Offer the membrane up to the vault ceiling along the centre line of the vault, and drill and hammer home the fixing plugs in a straight line at 600mm centres from front to rear. These will provide fixing points for the dry lining system.

The creased downturn at either end of the vault will start to deform going into the curvature of the vault ceiling. Where this occurs, carefully slit / cut the deformed sections towards the crease but stop short of the crease by one stud.

The membrane can now be overlaid and will flatten out and follow the curvature. Several slits may be required to achieve this depending on the radius of the vault.

Continue to work out from the first sheet, ensuring a weathered joint of not less than eight studs. The flange should be used to make both of these weathered joints either side of the initial membrane fixed off the central line of the vault. 

The weathered joints are sealed flange over stud using Platon Sealing Tape.

All the sheets running from front to back of the vault are cut overall length of vaulted soffit. This should give coverage to the vault, past the springing line down to the floor slab line, together with a 200mm return to either end of the vault.

The end walls are now ready to be lined with the membrane. The end wall sections are cut to the true width of the vault so that the membrane overlaps the membrane returns already formed. These sections of membrane are fixed and sealed in exactly the same way as described for wall application. The end wall membrane stud to stud joint should be sealed around the radius with Platon Sealing Rope and if necessary Platon Corner Strip.

The floor membrane is now ready to be laid over the completed drainage system.

Data Sheets

Technical Data Sheet

System Platon Installation Manual

Platon Cavity Drain Systems Brochure

BBA Certificate

Declaration of Performance (DoP)

NBS Plus Product Entry

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