Quarry tile shock - what to do?

[ManorPiggy]

Hello - have done much googling and discussed with husband but really not sure what to do so thought I'd ask on my 'go to' place.

Just about to have our rear extension finished. Existing house is 1920s semi. We always thought our kitchen was concrete slab but having just ripped it out and taken up the lino (as it now flows into the new rear extension)...we discover it is 4mm of compound, some failed bitumen and quarry tiles on what I guess is soil. Which is not good. Overnight we now have some damp patches coming up where we took off some cracking compound yesterday. We live in an urban chalk valley less than 50m from a stream so risky for damp as it is. So choices seem to be redo what they have obviously done before but hopefully make a better job of it, or dig it out (don't want to restore quarry tiles as despite age of house it is not a character property and they look to far gone). Has anyone else faced this issue with a quarry tile floor and what did you do? If you dig out how much did it cost? The kitchen is 12sqm

It was typical to put down quarry tiles on earth floors.

I would get the whole lot up and get a new concrete floor. Then screed it and lay the new floor. Levels might be an issue but if your bass is earth you really have to start again for a lasting result.

I guess some would say just put a membrane over the tiles and screed but I’d be wary of that. It’s possible but not the best solution.

Yeah, I'm partly thinking best to pay more now before we put in our lovely new kitchen rather than store up an issue. For some reason I worry that we will create another issue e.g. something to do with the walls or foundations though this isn't based on anything in particular. Thanks

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Foundations won’t be affected by digging out a floor. At least by putting in a new floor you can control levels and quality of materials.

We had this and did exactly as TizerorFizzsuggested... Unfortunately the damp that was present still wanted to escape but now couldn't come through kitchen floor, so, as while house was built on earth (normal for the time) it found its escape at the perimeter of our new impervious kitchen floor so was sticking up the walls. We ended up with black mould growing on the wall which divided lounge and kitchen.
Whatever you do to your kitchen floor you need to give the present moisture an acceptable (structurally) escape route.
Suggest you do the plan but include a drainage pathway of some sort (which you can take out under your walls into garden or whatever). If you don't do this you will just push the problem to another part of your house...

@topcatstophat that is what worries me. The extension is suspended bison beams and the existing living room is suspended wooden flooring so I hope that might help but maybe it won't. Will look at drainage options. Thanks!

Do you have decent foundations and a dpc? Air bricks under the floors? With standard construction you really shouldn’t get damp coming up the walls. If will all depend on floor levels and ground levels outside. The ground outside cannot be higher. If you have cavity walls you shouldn’t have an issue. Damp doesn’t affect every house but you could investigate tanking if you are worried. Like a cellar.

I really appreciate your advice @tizerorfizz . Technically the house is single skin but with the additions most of the external is now cavity. Foundations seem as ok as you'd expect for 1920s cheap housing stock. Husband thinks probably injected DPC. Nothing bad noticed when they dug the new foundations. We have drainage on the front drive and in front of the remaining single skin bit and I think it is all fairly flat.

OK - slightly less worried now - wonder if it is a bit like looking up a health issue on google and suspecting the worst!

If you are worried I might be inclined to ask a surveyor about what solution would work best with the construction eras you have. You obviously don’t want issues but I would say it’s important to ensure each age of construction doesn’t allow damp into the house. I’m sure someone actually seeing it could advise.,

Yes that is a good idea to ask a surveyor - thanks

A 1920's house is pretty sure to have a DPC in the walls. Have a look to see if it has been bridged by paving on the outside. Rectify if so and there is no reason the walls should be damp.

While digging look for and replace any old pipes and broken drains (salt glazed clay drains are usually always cracked and leaking) and there will be one close to the kitchen sink and the soil pipe.

Your new floor can have a DPM, insulation, and concrete slab isolated from the walls, and will be much better than you had before.

It's an everyday job.

Thanks PigletJohn - hadn't thought about old pipework. I have probably been overthinking it but your last sentence helps. DH and I have laid a garage pad before so not complete novices but obviously this is a bit more important to get right!

IME damp in a kitchen floor is usually due to pipe or drain leaks.

Maybe yours is different, but take advantage of the digging to renew it.