Tiling over quarry tiles - Tile Advice

[Bezz]

Hi I'm looking for some advice on tiling over quarry tiles in my porch with some new ceramic tiles.
The existing tiles are sound and generally level, so my plan is to apply self levelling compound over the top to get a nice smooth surface, and then tile on top.
My only concern though is that my house is a 1930s semi, so there may be no dpm under the tiles. Will this cause me any issues with the above approach?

 

[Bond]

I see that a chemical dpc has been installed 3 courses above the tiled floor, so you may well potentially have damp issues.
Might be worth installing a dpm or using a moisture permeable tile.

 

[Bezz]

I see that a chemical dpc has been installed 3 courses above the tiled floor, so you may well potentially have damp issues.
Might be worth installing a dpm or using a moisture permeable tile.

Thanks but how do you suggest I install a dpm? I'm thinking of a liquid type application, but any suggestions of make/type will be helpful. Will i be able to apply the levelling compound over this?

 

[Bond]

Thanks but how do you suggest I install a dpm? I'm thinking of a liquid type application, but any suggestions of make/type will be helpful. Will i be able to apply the levelling compound over this?

You could go for something like a cement based tanking system ( paint on). I personally would break-out the existing floor and concrete and lay new concrete floor with insulation boards under and around the wall perimeter and a 300 micron polythene damp proof membrane, this would help reduce cold bridging, low level condensation which l suspect maybe an issue also.

 

[Bezz]

Would something like Ardex dpm 1c do the job?

 

[Bond]

Would something like Ardex dpm 1c do the job?

The issue with a surface paint on system is that you may be transferring additional moisture from the ground via floor slab into the walls. A damp proof membrane should be continuous with the damp proof course in the walls to be fully effective.

 

[Spare Tool]

Only concern with a DPM over the tiles if there isn't one underneath is it could end up forcing the moisture out and end up creeping up the walls..
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The issue with a surface paint on system is that you may be transferring additional moisture from the ground via floor slab into the walls. A damp proof membrane should be continuous with the damp proof course in the walls to be fully effective.

Beat me to it by 3 seconds....good advice 👍

 

[Bezz]

Will the chemical dpc already installed 3 courses above the floor stop this from happening?

 

[Bond]

Will the chemical dpc already installed 3 courses above the floor stop this from happening?

Highly unlikely, as it has been injected into the brick, moisture rising in a brick wall by capillarity will in the most part be transported in the bedding mortar. The effectiveness of chemically injected dpc’s on the whole is questionable.

 

[Bill]

Why are you worried about rising damp?

Look at the floor you have now....I see no issues with damp in the porch.

Just use a tile that can be used for external conditions.

 

[Bezz]

Why are you worried about rising damp?

Look at the floor you have now....I see no issues with damp in the porch.

Just use a tile that can be used for external conditions.

Tom I agree no damp issues at present. Correct me if I'm wrong, but my concern is that if I add a floor levelling compound, plus adhesive and then tiles, then the moisture that would normally evaporate will have nowhere to go and the levelling compound/adhesive will fail. For info the tiles I have purchased are large ceramic floor tiles.

 

[Spare Tool]

I don't particularly think the adhesive will fail, but do believe in covering them the moisture could be forced out and up the wall..maybe a natural stone would be better than ceramics

 

[Bond]

On the photo there appears to be some evidence of damp in the corner immediately above the floor, peeling paint and what appears to be damp staining showing through, also the remedial installed dpc would suggest damp issues in this area.

 

[Bill]

How do swimming pool tiles stay affixed if damp affected the adhesive?

Some times you lot over complicate jobs.

On a personal note, I like the tiles as is - perfectly suitable for a period porch.

 

[Tiler Durden]

Agree with Tom. Porch looks spot on as it is and in the real world that would probably just be tiled on and last many decades without issue despite the excellent Damp proofing advise that has been given. Sometimes you’ve just got to get on and do these things.