Delta FM - Damp Proof Floor Membrane (4mm Stud)

Delta FM - Damp Proof Floor Membrane (4mm Stud)

Delta Membranes | Damp Proof Floor Membranes

Delta FM is a High Quality, 4mm Stud, Damp Proof Floor Membrane manufactured from Virgin High Performance PE-VHD.

Delta FM is specifically designed for floor applications to combat capillary dampness and contamination. However, Delta FM membrane can also be used on walls typically where the wall finish to the damp proof membrane is timber battens, a dry-lining frame or block wall.

  Delta FM is supported by BBA Certification Certificate Number 00/3742.

Available in (W) 2.0M x (L) 20M (40M²) Rolls.

  Read our Guide on 'How To Identify & Treat Rising Dampness On Walls' and 'How To Install a Damp Proof Membrane'.


Delta FM Damp Proof Floor Membrane

Delta FM is a High Quality, 4mm Stud, Damp Proof Floor Membrane manufactured from Virgin High Performance PE-VHD.

Delta FM is specifically designed for floor applications to combat capillary dampness and contamination. However, Delta FM membrane can also be used on walls typically where the wall finish to the damp proof membrane is timber battens, a dry-lining frame or block wall.

The low stud profile (4mm) minimises the impact upon existing floor levels but still provides an air gap to achieve damp pressure equalisation. The special low profile offered by Delta FM is excellent for detailing existing staircases and tight spaces. Delta FM can be linked to other Delta MS membranes.

A fast-track application which allows for various floor finishes to be achieved with zero ‘down time’. Delta FM can be used in new build, remedial or refurbishment projects for floors and walls.

Delta FM can also be used in conjunction with thermal installation, sound insulation and numerous types of underfloor heating systems.

  Read our Guide on 'How To Identify & Treat Rising Dampness On Walls' and 'How To Install a Damp Proof Membrane'.

Benefits & Features:

  • Type C Drained Protection in accordance with BS 8102:2009

  • BBA Approved

  • Fast track application

  • RH Levels are isolated in the air gap and controlled.

  • A reversible system, which will minimize damage to historical or heritage structures

  • Virgin High Density Polyethylene Studded / Moulded Sheet (HDPE)

  • An effective barrier to the transmission of salts, liquid water and water vapour

Typical Applications:

Delta FM is suitable for use on damp proofing walls, floors and vaulted ceilings, above and below ground, in new construction or in existing buildings over a contaminated or damp background.

Delta FM can support a dry lining, screed or flooring, in the following situations:

  • On damp floors in situations subject to perennial moisture.

  • In conjunction with Remedial DPC Systems where the walls and floors have a high salt content and / or it is necessary to complete the installation immediately without allowing a period for initial drying.

  • Over walls and floors which have a friable or painted surface, are contaminated (eg with oil or mould), or have a high salt content.

  • As a waterproofing membrane in areas subject to vibration.

Depending on the application required and the site conditions, the membrane may be used as:

  • An underfloor Damp Proof Membrane

  • A dry lining for walls, ventilated into the room via aeration slots at the top and bottom of the wall or via passive air vents, where access through an external wall is available

  • A sealed system covering wall, floor and ceiling with provision made for disposing of water build-up behind the membrane via a sump and pump.


  • NBS Specification J40 (Clause 290) Flexible Sheet Tanking / Damp Proofing.

  • BS 8102:2009 Type C Drained Protection

Technical Data:

Membrane Material Virgin High Performance (PE-VHD)
Membrane Thickness 0.6mm
Stud Depth 4.5mm
Air Volume Between Studs 2.6L/M²
Compressive Strength 500 kpa
Temperature Resistance
-30°C to +80°C
Resistance to Fire (BS EN 13501-1) Class E

Floor Installation

Preparation to Existing Floors:

Scrape the surface clean, remove mortar ‘snots’, loose tiles, vinyl flooring, carpet etc. Vacuum clean to remove grit and dust. Floors must be level, flat and sound.

Preparation to New Floors:

Allow the concrete or screed to set hard enough to walk on. Vacuum clean to remove grit and dust. Apply a moisture resistant levelling compound if the floor is very coarse or uneven. Delta FM can be laid when the RH is 95% or less.

Installation Method:

Start with the flange (Flat section to one edge of the roll) at either one of the two longest walls. Roll out the first length of membrane and cut a length of membrane off the roll that is 200mm longer than the room length.

Delta Corner Strip is then applied above the butted joint to join the two widths of membrane. Apply more pressure with the palm of your hand to further seal the whole of the joint. A Hot Air Gun should be used to help sealing, especially in cold or damp conditions.

Where the floor membrane is required to be jointed to horizontal DPC’s, such as DPC Roll, through internal and external walls, these joints should be sealed with Delta Tape. Ensure both surfaces are clean and dry before attempting to make these joints.

If there are any services through the floor, the membrane can be cut and trimmed around them, and the gap filled and sealed using a high quality MS or SMX Polymer Adhesive. If necessary, a patch of membrane or Damp Proof Course (DPC) is laid over and sealed to the service with Delta Rope, and around its perimeter with Delta Tape. It should be noted that protrusions through the floor slab / raft should be avoided wherever possible as they create weaknesses that allow unnecessary water ingress.

The specified floor finish can now be laid directly over the floor membrane, which must not be punctured by any fixings through the floor. When a timber floor finish is preferred you must allow an expansion gap around the wall edge.

Speak to the supplier of the floor finish to confirm the correct size of this expansion gap.

Wall Installation


Clean the substrate to remove all loose debris and organic matter. Plaster should be removed as it can soften over time, which will weaken the fix of the membrane to the wall. If the wall render is in good condition, it does not have to be removed and Delta FM can be fitted directly over. Loose or crumbling render should be removed.

If evidence of bacterial growth can be seen, use a fungicidal product prior to the fitting of the membrane.

If any evidence of wet rot or dry rot is seen, have it dealt with by a qualified remedial specialist.

If a new slab is to be laid as part of the works, it is preferable to fit Delta FM prior to the laying of the floor slab with the floor DPM extending upwards in front of Delta FM ready for the concrete placement.

Cutting to Size:

Delta FM can be cut with a sharp utility knife, scissors or shears. Decide whether the membrane is to be fitted horizontally or vertically.

Membrane Jointing:

The installation of Delta FM can be fixed to walls either vertically or horizontally, however 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 Delta Tape, but this method is more manageable and much easier to fix.

Fixing to the Wall:

Delta FM is fixed to walls with Delta Qwik-Seal Plugs, or with Delta Plugs wrapped with Delta Rope. This will form a seal with the membrane when the plug is driven home into the substrate.

Cut the membrane to size. Ideally, Delta FM should be continued up into ceiling voids and down past the slab to the oversite. If this is not possible, cut the membrane so that it finishes tightly to the soffit and floor finish. A gap is not required at the soffit or floor, indeed the system works more efficiently when the system is not ventilated as this impedes the natural vapour drive from inside the property to the outside that still continues through the Delta FM.

Delta FM is fitted to the wall with the studs facing the wall and the flat surface facing inwards towards the applicator. Fix the membrane to the wall with Delta Qwik-Seal Plugs to all substrates except to slightly friable mortar substrate, when Cob Plugs should be used.

Delta FM can be fitted horizontally or vertically. Fit the membrane as level as possible - best results are achieved when a long builders level or a rotating laser level is used.

Using a 10mm drill bit, drill through the membrane into the wall to a depth of at least 60mm. Fix only as many plugs as are required to fix the membrane neatly to the wall

If fixings are required for fixing of timber battens, brackets for Gypliner type dry-lining frame or wall ties, add further plugs to the correct centres required for the wall lining.

Hammer the plugs home using a wide headed hammer such as a lump hammer or mallet.

Fit Delta FM to return walls to isolate wall finishes from dampness transmitting from the main wall being treated. Delta FM can be taken into reveals.

Using Delta Qwik-Seal Plugs For Fixing:

Delta Qwik-Seal Plugs have a hollow core that is designed to receive 5mm self-tapping screws. Use these to secure timber battens or locating brackets from wall lining systems.

Heavier items can be supported by screwing a piece of chipboard to the plugs at fairly close centres and then fixing the heavier item to the chipboard in a conventional way

Fixing Heavier Objects to the Wall:

Heavier objects should be attached to the wall using resin anchors. Seal around the resin anchor with Delta Than Waterproof Mastic.

Data Sheets

Delta Cavity Drain Systems Brochure

Delta Ancillary Products Brochure

Declaration of Performance (DoP)

BBA Certificate

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