Tiling floor, no DPM. Advice Please

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berty3000

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Hi all,

My house is a 1961 bungalow. The kitchen has a tiled floor that looks as though it was laid about 30 years ago. Under the cupboards, they left some gaps and you can see an old quarry tiles in some places, so that was the original floor over the concrete sub-base. There won't be a DPM under this.

It appears that these old quarry tiles were mostly removed as the more recent tiles, when seen in cross section, only seem to have grout under them quite thick.

Anyway, I'm planning to take the tiles up and have them replaced as part of a renovation. The concrete base will need some self levelling screed before new tiles go on.

I am not aware of any damp problems in that room and there is no obvious discolouring to the tiles or grout and none of them have blown, so my preference is not to bother putting down a liquid DPM or similar, which could introduce new issues like moisture going up the walls. I am happy for humidity to come through as it probably already does and just ensure adequate ventilation in the house. In other words, have a breathable situation. It is for this reason that I want tiles rather than click flooring as I assume any humidity will be able to make its way through the grout and into the air.

With all this in mind, is there any type of grout I should avoid, or a particularly good one that will remain stable and breathable in this situation? Also, will a latex screed be best or will any do?

Many thanks!
 
I don't see a need to go out of your way to ensure it's breathable. In 1961 they should have used a DPM in the walls, but even without one I don't understand your logic that sealing the floor would make water somehow squirt up the walls. It would just stay in the concrete or sink back into the ground. Water evaporating from the concrete will make 0.buggerall% difference to the overall ground water content and therefore the ability of the walls to wick up the moisture.

Glazed tiles are completely waterproof. I tiled a modern, dry room here with grey grout 2 years ago. The grout is still dark in some places, the water is still finding its way out from behind the tiles.

Seal it or don't seal it, it will be pretty much sealed once you tile it. But I don't see this as an issue, it's just good, I'd suggest you shouldn't worry about it.

Generally, all damp-proofing between the outside world and the interior is a good thing, with no downside.
 
If it's damp then use the powdered (cement based) tile adhesive rather than the ready-mixed stuff, which is much less water resistant.

The powder stuff would set underwater, water just makes it stronger.
 
The quarry tiles were the DPM.

Floors don't need to breath. The opposite really.

Use a liquid surface DPM.
 
^woody^ said:
The quarry tiles were the DPM.

Floors don't need to breath. The opposite really.

Use a liquid surface DPM.
Click to expand...

Correct.

Not that it needs to breathe, but it already does so and there is no harm.

Installing a DPM might introduce problems that don't currently exist plus I have to pay for it.
 
Ivor Windybottom said:
I don't see a need to go out of your way to ensure it's breathable. In 1961 they should have used a DPM in the walls, but even without one I don't understand your logic that sealing the floor would make water somehow squirt up the walls. It would just stay in the concrete or sink back into the ground. Water evaporating from the concrete will make 0.buggerall% difference to the overall ground water content and therefore the ability of the walls to wick up the moisture.

Glazed tiles are completely waterproof. I tiled a modern, dry room here with grey grout 2 years ago. The grout is still dark in some places, the water is still finding its way out from behind the tiles.

Seal it or don't seal it, it will be pretty much sealed once you tile it. But I don't see this as an issue, it's just good, I'd suggest you shouldn't worry about it.

Generally, all damp-proofing between the outside world and the interior is a good thing, with no downside.
Click to expand...

There is no DPM in the floor, there is a DPC in the walls.

Are you saying that humidity cannot pass through the grout that is beneath and between tiles?
 
^woody^ said:
Like what?
Click to expand...
Moisture that might rise into the air in a very gradual way as humidity building up beneath the DPM and then blowing it or tiles? Or making its way up the walls instead (floor level is oddly slightly above DPC in my house, although usually separated by a gap, don't ask me why).

Point is, there's no problem right now, so seems safest to just remove existing tiles and them do new tiles over the the surface that the original quarry tiles were put on. I.e. rinse and repeat. Question is, which grout is best to allow some moisture to pass through and survive potential moisture (I mean humidity, not a fountain of water bursting through the sub base).
 
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