S
Sutwam
Hi Gixer, I have this tech sheet for a Dural Wp matting, but all these mattings fix in a similar way so I thought it might be worth you seeing it. Good luck with it!
WP Membrane
Technical advice on installation.
The benefit of WP membrane is that it is waterproof
The problem is that the WP membrane is waterproof,
This prohibits the curing or setting of dispersion type adhesives normally used to fix wall tiles.
Dispersion adhesives are ready mixed that come in buckets ready to apply. When used with tiles the water in the adhesive “disperses” into the biscuit of the tile and into the absorbent substrate such as plaster or plaster board. The adhesive then dries hard.
When the WP matting is used this dispersion cannot happen as quickly as the water cannot escape through the membrane and must only go into the substrate, eventually being absorbed.
The net effect is a slow bond between the WP and the wall substrate.
This is governed by the rate of absorption of the moisture from the adhesive
The trowel used to apply this initial bond layer has small serrations of 3 – 4mm. This reduces the amount of adhesive and therefore moisture behind the WP membrane.
As soon as a good bond is achieved, the tiling onto the surface can take place. With dispersion adhesive the only place the water can go is into the tile biscuit or escape through the grout lines. The adhesive at the edges of the tiles sets hard forming a perimeter ring around the edges of the tiles. The adhesive in the middle can remain un-set and liquid. This can be viewed as a “picture frame” effect. This is not a good thing for safety.
The use of Porcelain tiles, which absorb little or no water, means that the adhesive will never actually set!
For these reasons we recommend that a hydraulic type adhesive is used, (commonly known as Bag or Powder adhesives, this type of adhesive sets chemically with the addition of water and will even set under water). However this raises another difficulty. Most wall substrates in domestic housing are covered with Gypsum plaster. The cement in hydraulic adhesive reacts with plaster and a substance called Ettringite is created. This substance gains in volume as it is created and causes pressure in the same way that freezing water becomes ice and cracks pipes. This volume change can cause WP membrane to debond.
Therefore it is vital that any plaster surfaces must be suitably protected by priming or that a special adhesives that will not react to the plaster is used for this initial bond.
The use of hydraulic adhesive to bond tiles to the surface of WP is more successful. Even with the waterproof nature of the WP membrane the adhesive will always set and harden. This is also the case with porcelain tiles.
In summary the water proof nature of the WP membrane makes the use of dispersion adhesives difficult, unreliable and slow. Success will be achieved by using the right hydraulic powder adhesive with care taken to ensure any necessary priming has been completed on the substrate.
Key points
WP Membrane
Technical advice on installation.
The benefit of WP membrane is that it is waterproof
The problem is that the WP membrane is waterproof,
This prohibits the curing or setting of dispersion type adhesives normally used to fix wall tiles.
Dispersion adhesives are ready mixed that come in buckets ready to apply. When used with tiles the water in the adhesive “disperses” into the biscuit of the tile and into the absorbent substrate such as plaster or plaster board. The adhesive then dries hard.
When the WP matting is used this dispersion cannot happen as quickly as the water cannot escape through the membrane and must only go into the substrate, eventually being absorbed.
The net effect is a slow bond between the WP and the wall substrate.
This is governed by the rate of absorption of the moisture from the adhesive
The trowel used to apply this initial bond layer has small serrations of 3 – 4mm. This reduces the amount of adhesive and therefore moisture behind the WP membrane.
As soon as a good bond is achieved, the tiling onto the surface can take place. With dispersion adhesive the only place the water can go is into the tile biscuit or escape through the grout lines. The adhesive at the edges of the tiles sets hard forming a perimeter ring around the edges of the tiles. The adhesive in the middle can remain un-set and liquid. This can be viewed as a “picture frame” effect. This is not a good thing for safety.
The use of Porcelain tiles, which absorb little or no water, means that the adhesive will never actually set!
For these reasons we recommend that a hydraulic type adhesive is used, (commonly known as Bag or Powder adhesives, this type of adhesive sets chemically with the addition of water and will even set under water). However this raises another difficulty. Most wall substrates in domestic housing are covered with Gypsum plaster. The cement in hydraulic adhesive reacts with plaster and a substance called Ettringite is created. This substance gains in volume as it is created and causes pressure in the same way that freezing water becomes ice and cracks pipes. This volume change can cause WP membrane to debond.
Therefore it is vital that any plaster surfaces must be suitably protected by priming or that a special adhesives that will not react to the plaster is used for this initial bond.
The use of hydraulic adhesive to bond tiles to the surface of WP is more successful. Even with the waterproof nature of the WP membrane the adhesive will always set and harden. This is also the case with porcelain tiles.
In summary the water proof nature of the WP membrane makes the use of dispersion adhesives difficult, unreliable and slow. Success will be achieved by using the right hydraulic powder adhesive with care taken to ensure any necessary priming has been completed on the substrate.
Key points
- Use a fine notched trowel on the initial coat.
- Prime or use a special adhesive to allow tiling onto Plaster.
- Use hydraulic adhesive.
