HELP! Do we need a DPM before laying tiles

[Sam2494]

Hi, We've just finished pulling up old quarry tiles ready to fit new Porcelain tiles throughout! Had to remove quarry's due to levels of external doors, were unsure what the subfloor is beneath the quarry's, I believe the property is prone to rising damp seeping through subfloor as no DPM.

I'm hesitant to lay self levelling onto subfloor incase moisture seeps through and blows it to bits and then everything will need to be ripped up!

I know you can get liquid DPM but would we get away with just tiling straight to sub base with Mapei Flexible adhesive? It's both flexible and completely waterproof so the damp shouldn't effect it at all? Or disrupt the new tiles? (Water may sit underneath I know as porcelain isn't a breathable covering like quarry tiles)

Has anyone got any advise or any pointers please?

Thanks

Attached is a picture of the subfloor now the quarry's have been taken up.

 

[Albert]

Hi, We've just finished pulling up old quarry tiles ready to fit new Porcelain tiles throughout! Had to remove quarry's due to levels of external doors, were unsure what the subfloor is beneath the quarry's, I believe the property is prone to rising damp seeping through subfloor as no DPM.

I'm hesitant to lay self levelling onto subfloor incase moisture seeps through and blows it to bits and then everything will need to be ripped up!

I know you can get liquid DPM but would we get away with just tiling straight to sub base with Mapei Flexible adhesive? It's both flexible and completely waterproof so the damp shouldn't effect it at all? Or disrupt the new tiles? (Water may sit underneath I know as porcelain isn't a breathable covering like quarry tiles)

Has anyone got any advise or any pointers please?

Thanks

Attached is a picture of the subfloor now the quarry's have been taken up.

View attachment 92950

The water has to go somewhere my guess is it will travel under tiles until it reaches
a point of escape normally the walls that suround the room

 

[Sam2494]

Yeah that's what we would guess, the previous tenant had laminate and carpet down on quarry tiles and they had slight rising damp but since that has been sorted with more internal ventilation!

Our main worry is putting down self levelling onto the sub floor now quarry tiles are up incase there is no DPM and the damp gets into the self levelling and blows it to bits!

 

[Dumbo]

Some levelling compounds ( they don't self level ) can deal with moisture to a certain extent . Ardex arditex na is one and I believe ultra level it 2 is another as their aggregate doesnt expand when it gets damp .

 

[Bond]

As above if your floor slab is subject to rising damp, you may move the dampness to abutting walls. If the DPC is below the level of the damp slab, this will have the effect of transferring moisture into the wall structure, and potentially causing damp and decay. If moisture is eminating from sub-soil, the slab may also be harbouring hygroscopic and efflorescent mineral ground salts, which may be damaging ( break down) slc, adhesives and or waterpoofing.

 

[Bond]

Should have said above, whatever you apply to your concrete slab, you should first consider using an anti-sulphate solution , as a salt barrier.

 

[Sam2494]

All that informations great thanks!

There are 2 courses of blue brick above the level of the floor slab so surely that's the DPC?


Will have a look into those self levelling compounds above

 

[Bond]

Aye, two courses of blue engineering bricks, are used as a damp proof course. That should protect your walls from rising damp, providing the bedding mortar is not porous.

Another thing to perhaps consider is the potential cold bridging effect at the wall slab interface. ( causing condensation).

 

[Sam2494]

That's spot on thanks for the help! Our only concern now is this self levelling and how it's going to react with the floor slab of there is no DPM

 

[Sam2494]

Just read that the ardex arditex & Ultra level are moisture resistant like said above and can be used underneath a DPM so surely that would be perfect for us if we treat the slab with an anti sulphate solution prior to pouring the self levelling and then once gone off we'll be sound to tile straight on top?

 

[Bond]

If manufacturers say it can be used under a dpm ,then you should be good to go. I would also give it a coat or two of SBR over the anti-sulphate a its resistant to moisture and salts.

 

[Sam2494]

Cheers for the help, what is SBR?

 

[Bond]

SBR is a white liquid ,sealer,primer,and admixture, widely available in builders merchants, diy outlets, etc.

 

[Spacey360]

Most latex based SLC are moisture tolerant

 

[Sam2494]

Have decided to go with the following plan of action:
1. Permaguard Epoxy DPM throughout (2 coats)
2. Self levelling compound
3. Install new tiles using Mapei flexible waterproof adhesive

Does this sound sufficient and any more pointers?