Good Water resistant thick bed floor adhesive - TilersForums.com

[hmtiling]

What's not the case in relation to lime screeds?

A lime screed will function without a dpm

 

[Bond]

A lime screed will function without a dpm

Okay cheers, have no knowledge of lime screeds.

 

[Sam2494]

Yes I know the quarry's were there because they are a breathable covering, yes it is fundamental in new builds and builds over the last 50 years however I'm working on a 1940/30's property so no integral DPM under the floor slab, used slate for internal dpc of walls and 2 course of blues for external!

We are laying porcelain tiles throughout (yes I know they aren't breathable) however after speaking with Ardex & Mapei technical departments both said exactly the same, no need to use a DPM, only real need for DPM is with timber & vinyl floors. Even with us laying porcelain floor will breathe through grout joints & eventually moisture will make its way through. Cement based adhesives will not be effected by damp they both told me along with Ardex NA self levelling. Natural salts in the ground may cause some essofflerecent coming through grout however chance of this is unlikely.

 

[Andy Allen]

We need @Ajax123 on this..... He's the screed expert..

 

[Bond]

Yes I know the quarry's were there because they are a breathable covering, yes it is fundamental in new builds and builds over the last 50 years however I'm working on a 1940/30's property so no integral DPM under the floor slab, used slate for internal dpc of walls and 2 course of blues for external!

We are laying porcelain tiles throughout (yes I know they aren't breathable) however after speaking with Ardex & Mapei technical departments both said exactly the same, no need to use a DPM, only real need for DPM is with timber & vinyl floors. Even with us laying porcelain floor will breathe through grout joints & eventually moisture will make its way through. Cement based adhesives will not be effected by damp they both told me along with Ardex NA self levelling. Natural salts in the ground may cause some essofflerecent coming through grout however chance of this is unlikely.

Crystallasion of salts often causes swelling and forces thus generated can cause adhesive failure. ( especially with a relatively impervious tile) . Unlikely l know, nevertheless possible.

 

[Sam2494]

But with moisture being able to breathe and make its way through grout joints this is unlikely to happen, like you say not impossible though.

 

[Bond]

Salts will accumulate where moisture is evaporating e.g. They come out of solution and crystallise, on or near the evaporating surface.

 

[Andy Allen]

Tape some plastic to the floor for a few days and see how moist it gets.

 

[Martyn Leeds]

Why not just use a liquid dpm, ardex I think

 

[Sam2494]

Yes Ardex technical advised that salts could cause essofflerecent as like you say they will accumulate when they make there way through the grout joints,however the chances are highly unlikely unless we live near a lot of waste land where salts in the ground will be high.

My view was to use a epoxy DPM however both Ardex & Mapei said not to waste the money as like I've said before they said it's not necessary if tiling the floor.