Void under floor information and advice on general building topics, builders merchants, problem builders, DIY Stores etc....

[jonmy]

Hi - I am currently having my kitchen renovated. When the contractor started relevelling the floor - preparatory to laying porcelain tiles to go on top - it broke through in part of it to reveal a void beneath of about 60 cm depth (maybe more). Some rising damp is visible on the walls too and it's not clear where this is coming from. The void area in question is about 530 cm x 270 cm. I have been given a number of options:

1. fill the void with concrete and lay a basic cement floor
2. construct a steel reinforced concrete floor
3. Put joists in above the void and then lay a wooden floor on top


Number 1 is the cheapest quoted at a few hundred pounds rising to several thousand for number 2. Based on discussions with independent people my feeling is that the wooden flooring option is best but my contractor says this is going to be very expensive and difficult. Would anyone know if his response is justified, what might be the best option, and what reasonable prices should be?

Thnx

[rosebery]

So what is the current floor?

Cheers

[jonmy]

It had a concrete floor approx 8cm thick.

[rosebery]

Thats not very thick I guess but then again my house is only sitting 9" foundations and its been there for over 70 years. The question is - is it rotten which is why it broke through or is it OK and someone was incompetant and broke through it when levelling out a high spot? If the former then it should be replaced - if the latter why hasn't he suggested repair?

Option one is the simplest solution - open up the hole and pour it in having taken damp precautions of course. But then you have to wait for it to cure and that could be a while.

I do not see the point of Option 2 at all. You are replacing a kitchen floor not building a high rise!

I would have thought that option 3 was the best solution TBH. Does your builder mean difficult as in least easy and quick for him to do before he can submit his additional invoice or its too difficult technically?

Cheers

[jonmy]

Re option 3 he says it's difficult because of fitting joists to the wall and putting in air bricks. I can't see why myself it would be too difficult but maybe there is a technical reason I'm not aware of?

At the moment though the contractor has taken up all the concrete in question and broken it into hardcore. I think he intends to pour concrete over the top. However the hardcore while filling the hole would not allow a lot of concrete to be poured on top I feel. So I am concerned about this - I am going to end up with a thinner layer of concrete than I had to start. And I am concerned as well that if the void is still sinking lower the hardcore will settle lower pulling the new concrete floor. Does that sound like a lkely scenario?

[rosebery]

"Re option 3 he says it's difficult because of fitting joists to the wall and putting in air bricks."

Its only difficult because he doesn't want to do it.


"I can't see why myself it would be too difficult but maybe there is a technical reason I'm not aware of?"

It isn't and I can't see any technical reason why it shouldn't be done.


"At the moment though the contractor has taken up all the concrete in question and broken it into hardcore. I think he intends to pour concrete over the top."

So he's made his own decision without consulting you - naughty!


"However the hardcore while filling the hole would not allow a lot of concrete to be poured on top I feel."

You means its been broken up into large lumps. Not acceptable IMO. It needs a proper damp-proof membrane which cannot be put down properly if large chunks of broken concrete have been chucked in.


"So I am concerned about this - I am going to end up with a thinner layer of concrete than I had to start."

Then its pointless. Unless the concrete was rotten what was wrong with a "repair" option?


"And I am concerned as well that if the void is still sinking lower the hardcore will settle lower pulling the new concrete floor. Does that sound like a lkely scenario?"

I am not in a position to advise you on that.


Cheers