Wykamol Group | Damp Proof Membranes
Wykamol CM3 MESH Membrane is a High Quality, 3mm Stud, Damp Proof Meshed Membrane comprising of HDPE Membrane with a rot-proof HDPE mesh on the surface of one side, perfect for damp proofing. The meshed surface creates a mechanical key to allow the membrane to be plastered, rendered or to receive dot & dab plasterboard.
Wykamol CM3 MESH Membrane is supported by BBA Certification Certificate Number 18/5595.
Wykamol CM3 MESH Membrane is available in 1.0 Metre, 1.2 Metre and 2.0 Metre Widths.
Available in various Roll sizes ranging from 2.5M² to 40M².
Read our Guide on 'How To Identify & Treat Rising Dampness On Walls'
Wykamol CM3 MESH Membrane is a composite damp proof membrane comprising of HDPE membrane with a rot-proof HDPE mesh heat-welded during the manufacturing process to the surface of one side. The meshed surface creates a mechanical key to allow the membrane to be plastered, rendered or to receive dot & dab plasterboard.
Wykamol CM3 MESH Membrane is 0.5mm thick and has a pattern of raised 3mm studs. The studs face the wall and create air channels that allow for vapour equalisation to take place between the membrane and the wall.
Wykamol CM3 MESH Membrane is light, clean and easy to handle. It can be cut with a sharp knife, scissors or shears. The membrane is inert and is highly resistant to water, alkalies, saline solutions and organic acids, and it is not affected by minerals. It is also resistant to bacteria, fungi and other small organisms.
Wykamol CM3 MESH Membrane is guaranteed against deterioration for 30 years and has a life expectancy of at least 50 years.
Provides a surface that is totally separated and unaffected by the dampness within the wall, ensuring that the wall finish will never be affected by moisture or salts
Superb ‘key’ for renders or plasters
Completely moisture-resistant but allows vapour diffusion
Quick and easy to install
In many cases the existing render can be left on the wall
No requirement for damaging preparation to the wall surface
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 the Wykamol CM3 MESH Membrane can be fitted directly over. If the render is damaged, local repairs may be required
Loose or crumbling render should be removed and local repairs made. If the render is in very poor condition, all of it may need to be removed
Obtain as flat a surface as possible. If the wall is undulating, better results are produced if the wall surface is dubbed-out flat with sand & cement prior to installation of the membrane, rather than dubbing out over the top of Wykamol CM3 MESH Membrane. A flat, uniform surface to the substrate means that the plaster or render above Wykamol CM3 MESH Membrane will also be uniform and less likely to have cracking caused by differential thicknesses
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 Wykamol CM3 MESH Membrane prior to the laying of the floor slab with the floor DPM extending upwards in front of the Membrane ready for the concrete pour.
Wykamol CM3 MESH Membrane can be cut with a sharp utility knife, scissors or shearsDecide whether the membrane is to be fitted horizontally or vertically
Joints may be made horizontally or vertically
Joints are created by butt jointing the two edges together and then oversealing the joints with Wykamol Mesh Tape.
Wykamol CM3 MESH Membrane can be taken round corners. On particularly difficult shaped corners, cut the CM3 MESH Membrane and butt joint and seal as above.
The Mesh Tape should be firmly pressed into the mesh of the Wykamol CM3 MESH Membrane to facilitate the joint.
In cold and damp conditions a heat gun should be used to gently evaporate surface moisture and then to assist in pressing the Mesh Tape into the mesh of the membrane
Where the membrane has to be cut around pipes or other protrusions, carefully cut the membrane around the protrusion and then seal around the protrusion with Newton® Sealing Mastic to ensure there is no bridging between the damp substrate and the new finish.
Cut the membrane to size. Ideally, Wykamol CM3 MESH Membrane 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 Wykamol CM3 MESH Membrane.
Wykamol CM3 MESH Membrane is fitted to the wall with the studs facing the wall and the flat meshed surface facing inwards towards the applicator. Fix the membrane to the wall with Wykamol Ultimate Plaster Plugs. Or, if a seal is not required when fixing then use Wykamol CM Plaster Plugs instead.
Fix the membrane to all substrates except when fixing to plywood or timber, when a galvanised clout nail should be used, or to slightly friable mortar substrate, when the Cob Plug should be used.
Wykamol CM3 MESH Membrane 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. Care must be taken to ensure that the Wykamol CM3 MESH Membrane is pulled tight and square while fixing as this will avoid sagging or bulging which can cause problems when plastering or rendering.
Using a 7mm or 8mm drill bit (depending on substrate), drill through the membrane into the wall to a depth of the length of the Fixing Plug being used.
Use a small number of fixings to initially fit the membrane to the wall as level as possible.
Once the section of membrane is on the wall add the further fixings
Hammer the plugs home using a wide headed hammer such as a lump hammer or mallet
A smaller-diameter bit can be used on softer substrate to ensure a tight fit for the plug
Fixing centres internally must not be greater than 250mm
On curved or uneven surfaces, closer fixings should be used
On exposed areas closer fixings are recommended, to restrain possible thermal movement
Fit Wykamol CM3 MESH Membrane 300mm to return walls to isolate wall finishes from dampness transmitting from the main wall being treated
Wykamol CM3 MESH Membrane can be taken into reveals
Fixing should not take place above 30°C and below -5°C.
Wykamol CM3 MESH Membrane is suitable for wall finishes including plaster, render, hydraulic lime or plasterboard bonded to the membrane with a propriety adhesive compound.
Whilst cement based renders are prone to cracking, careful application can reduce or avoid this. Problems occur when the scratch coat has not been allowed to fully cure prior to the float coat being applied, but the most common problem we see is where the render has not been allowed to fully cure due to accelerated drying. It is extremely important that the render is slowly cured for a period of 7-10 days, longer if possible. The render gets its strength from the chemical processes that take place between the cement content and the added water. The cement needs the correct amount of water to be available to it during the whole of the curing period. If the render dries too quickly due to exposure to sunlight, wind or even dehumidification, the cement will not be able to react with water, producing a weak render that will be prone to cracking.
The render should be dampened regularly during the curing process and protected from accelerated drying with hessian and plastic sheeting.
Hairline cracking can be made good with fine fillers or alternatively a high-build masonry paint can be applied.
DO NOT APPLY DECORATIONS UNTIL PLASTERS OR RENDERS ARE THOROUGHLY DRY.
It is recommended that renders and plasters are raised from the floor by 20-25mm to prevent bridging from the floor. Newton 800 Finishing Profile, available in 2 metre lengths, should be fitted to the bottom of the Wykamol CM3 MESH Membrane as a plaster stop, guaranteeing that the plaster/render will stop short of the floor.
Newton 800 Finishing Profile must be fixed at the same time as Wykamol CM3 MESH Membrane and therefore before the plaster or render is applied.
Newton 800 Finishing Profile is not recommended where the run of wall is uneven or when the membrane is extended down past the slab. Once the finish has been applied and has dried, the 20-25mm gap to the bottom of the plaster / render should be covered by a timber skirting.
The recommended plaster for Wykamol CM3 MESH Membrane is Tarmac Whitewall One Coat. Please note that we do not recommend that this product is used in one single coat to our Mesh membranes.
The application of the plaster should be in two coats: 6mm scratch coat, 6mm second or float coat. If a finish coat is required this should be of 3mm.
Tarmac Whitewall should be applied in accordance with good plastering practice as described in BS 8481:2006, BS EN 13914-2:2005.
Always allow 24 hours drying time between coats of plaster. For a high impact resistant finish, use Whitewall High Impact Backing Plaster.
NOTE: Tarmac Whitewall and Tarmac Whitewall High Impact Backing Plaster are not suitable for areas of high humidity and wet areas such as swimming pool surrounds.
Render with a mix of sand, cement and lime should be applied in two coats using the procedures defined within BS EN 13914-1:2005 to a total thickness of 14mm. A 3mm skim coat of finishing plaster can be added once the render is fully cured
The scratch coat should be a mix of 1 part lime: 1 part cement: and 5 parts clean well-graded sharp sand. The second or float coat should be a mix of 1 part lime: 1 part cement: and 6 parts clean well graded sharp sand. The scratch coat should be 7mm and the second or float coat should be 7mm.
To lessen incidents of cracking, it is best to mix the lime and sand a day or more before use. Cement can then be added at the time of rendering.
The work should be of two coats of render and if required, a third coat of finishing plaster. The purpose of the 7mm scratch coat is to stiffen up the lath and to provide rough and absorbent, backing for subsequent coats. Work this scratch coat well into the mesh. Each 7mm coat of render should be allowed to dry for a period of not less than seven, preferably ten days, longer if possible. Cracking may occur if shorter time is allowed between coats.
It is important that the render coats are allowed to cure correctly over the 7 to 10 day period with the render dampened as required. If the scratch coat has not fully cured, slumping of the render can result.
Before applying the second or float coat, carefully drill or scratch out a small section into an area behind the mesh, within the membrane stud, to confirm that it is fully cured. The surface will cure quite quickly but the area behind the mesh must be fully cured also.
In warm periods the render should be protected from excessive drying out by covering with damp hessian sheets and plastic sheeting over it.
Dampen down the scratch coat before application of the float coat. A smooth finish is not recommended. Expansion joints should be trowelled in through the render to the membrane. These joints must be filled with a suitable flexible polymer-based sealant. Expanded metal angle beads and stop beads can be fixed where appropriate using dabs of the same material mixed as for the scratch coat.
NHL (Natural Hydraulic Lime) 3.5 should be used to a combined depth of 20mm with a 10mm scratch coat and a 10mm second or float coat. The mix ratio is 2.5 parts sand to 1 part NHL, 3.5 mixed as per manufacturers instructions. The 10mm scratch coat is pushed firmly into the membrane mesh.
Check the application the day after and rub out any cracks. The surface should be thoroughly scratched without breaking the surface of the mesh. The scratch coat has to be left for a minimum of 7 days to set. It should be protected from draughts and extremes of temperature.
Before applying the second or float coat, carefully drill or scratch out a small section into an area behind the mesh, within the membrane stud, to confirm that it is set and reasonably hard. The surface will cure quite quickly but the area behind the mesh that has to be set.
The second coat is the float coat and is applied then ruled off to flatten the wall surface. The mix ratio is 2.5 parts sand to 1 part NHL 3.5 mixed as per manufacturers instructions.
The scratch coat has to be dampened down before application of the float coat.
The work has to be protected and tended as per the scratch coat. The second coat is floated or trowelled so a finish coat or a further coat can be applied
Plaster board panels can be fixed to Wykamol CM3 MESH Membrane by the dot and dab method, giving a dry surface ready for immediate decoration. ‘Dabs’ should be applied to the heads of the Plaster Plugs, board edges and membrane to cover 50% of the Wykamol CM3 MESH Membrane.
NOTE: We do not recommend that laminated or insulated plasterboard is dot & dabbed to meshed membranes. Laminated boards have to be fixed to the wall with a mechanical fixing at each side of the board, just above half way up, so that the board does not come apart and block exits during a fire. This is a requirement of UK Building Code. It is not possible to mechanically fix through the laminated board without puncturing the membrane. If insulation is required to the wall build, use a Non-Meshed Membrane Damp Proofing Membrane (such as Wykamol CM3 Cavity Drain Membrane), with an independently supported wall frame.
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