Help please, gap under concrete floor

ema_o

As the title says really, help!!

We have a 1930s semi which we have been doing up (initially we were just doing it as and when, but now with baby on the way we are getting everything done in a big push (yay )

Half our house is joists and floorboards (the sitting and living room), however the other half (hallway, under stairs and kitchen) sits on what we thought was a solid concrete floor.

We are having the joists replaced in one of the rooms as some were rotten (also sorted out why they were rotten), however the guys doing it told us that the concrete floor is basically about 4 inches of concrete floating on a void of about another 4 inches (or more), and it looks like it is under all the floor in the hallway. There is hardcore underneath, but they think it has just compacted over time (it was junk more than hardcore and includes slate tiles and even a paint can?!?).

Obviously this is a worry, however more worrying is that we didn't need to replace the joists on the other side of the house, so we don't know whether this void continues through. We have just had a new kitchen put in (and covered in laminate flooring), I'm really not sure we can afford to move / refit the kitchen to replace the floor (although also we can't afford everything to start falling through the floor either :eek:).

I am just totally gutted that we were almost there with the house, I thought replacing the joists was the last big thing to do, then we could move on to decorating. Ideally we would sort it out without rippind everything up - is this possible, we think we saw something like this on Sarah Beeny (my hose is falling down) where they pumped something in to stop subsidence, also from googling I have started to read about something called slabjacking, although this seems to be done when the concrete has actually fallen, but intend to read a bit more about this to see if it will help.

Any opinions / advice would be hugely appreciated. We did ask the guys doing the other floor their advice and it was to break up the floor and start again - however I really hope there is an alternative at least for the kitchen area.

Em xx

Gloomendoom

It could be worse.

I had a similar problem... but I only discovered it when the floor caved in.

themacster

Could well be settlement due to inadequate original compaction and/or preparation of ground and/or hardcore. Where do you live? Any mine workings or other subterranean voids?

Uretek do the injected slab void infill

wallbash

4inches of concrete , no reason to think its damaged??
Resting on something ?? not moving .
Would not panic into doing anything . Might be a problem but then again could have been like that for last 50 plus years.

themacster

wallbash wrote: »

4inches of concrete , no reason to think its damaged??
Resting on something ?? not moving .
Would not panic into doing anything . Might be a problem but then again could have been like that for last 50 plus years.

Don't think Gloomendoom would share your viewpoint!

gmgmgm

Is your concern that a 4inch slab of concrete might break?

Concrete's pretty strong and it's clearly lasted this long. Some googling will probably tell you the largest unsupported span typical 4inch concrete will support. I expect it's absolutely fine for a consumer kitchen. Without an Aga.

themacster

That's alright if its reinforced - not very common for ground bearing slabs in houses of that age - maybe it is reinforced, but if not I certainly wouldn't want to carry on knowing it could collapse at any minute. Concrete is not strong in tension.

Gloomendoom

themacster wrote: »

Don't think Gloomendoom would share your viewpoint!

It had a silver lining. When I removed the concrete and 42 tons of hardcore underneath I discovered a cellar.

A free(ish) room.
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ema_o

I think from what they were saying it's not resting on anything. I'll check with OH as he had a look and update.

Our first thought was that it had been ok up to now, it's just that as we're planning on putting nice (laminate) flooring on top of it we'd rather do anything we needed to first. I did find the uretek solution, will give them a call and see, we might be a bit far from them.

Underneath the 4 inches or so of gap is the hardcore (rubble and rubbish), which fills half of our 6 foot cellar (this is empty under the other half of the house except for foundations). Perhaps there are some bits where the hardcore is still under the floor but not sure, OH said he could see to outside wall of house when he looked

Thanks for the thoughts and advice, all v appreciated

Em xx

Gloomendoom

ema_o wrote: »

Underneath the 4 inches or so of gap is the hardcore (rubble and rubbish), which fills half of our 6 foot cellar (this is empty under the other half of the house except for foundations). Perhaps there are some bits where the hardcore is still under the floor but not sure, OH said he could see to outside wall of house when he looked

Thanks for the thoughts and advice, all v appreciated

Em xx

Why not do what I did? Excavate the cellar and put in a new suspended floor over the top. It made some really useful space... perfect for my wine and beer collection.

wallbash

I think from what they were saying it's not resting on anything.

Not very clear. Or is it a miracle. Must rest somewhere.

think it has just compacted over time

But how long ?? if the rubbish settled quickly , as I expect the floor could easily have been , as I suggested been like that for many many years. If the rubbish ( can't call it hard core) has moved recently .... why?