Sinking Concrete Floor (Subsidence?), How To Repair?

bagels

I'd be very grateful for advice on how to solve a problem i have with my Hallway Floor.

My house is 30 years old and the front is on a slope.
At the point where my driveway meets the public footpath, it appears that the driveway has risen, leading me to suspect that the driveway is sliding down the slope.
This is what leads me to suspect that the fill underneath my Hallway floor is settling or sliding away.

I want to tile my hallway floor but am worried that the floor is unstable.

Frequently when i enter or leave through the front door and step on a certain part of the floor, i hear a distinct 'clunk' sound and get the feeling that the floor is giving way underneath me.
There is a crack on the floor near the front door, extending about a metre into the hallway.

I'm afraid theres a hollow area underneath the hallway floor that allows the floor to drop when stepped upon.
If the floor has movement in it, then i can't risk tiling it as the tiles would probably break due to the movement.

What can i do to accurately diagnose the problem & fix it?
Will i have to dig up the floor & replace it?
Is there any other solution, eg drill through the floor in several locations and inject something down into the hollow area (if it exists)?

I don't have any construction experience, just a bit of diy, so please excuse me if i've made a poor job of describing the problem.

Thanks in advance for any advice.

mickdw

I have seen floors with the hollow sound that you mention.
In your case, how old is the floor? Has it actually dropped(view along the skirting)?
If its over 20 years old and has not moved, its unlikely that it will now move however minor movements can crack tiles.

Seeing as you are hoping to change the floor finish anyway, it would not be a major job to break out alittle area and see what the story is. Its quite possibly just where the screed meets the subfloor under it that is allowing a tiny vibration to cause the clunk sound.
Even if you were to take up 5 or 6 sq.m. of floor screed and replace it, it would be a minor job, you could possibly do it in a day. If there is no plumbing in that area, it would be even easier

bagels

mickdw wrote: »

I have seen floors with the hollow sound that you mention.
In your case, how old is the floor? Has it actually dropped(view along the skirting)?
If its over 20 years old and has not moved, its unlikely that it will now move however minor movements can crack tiles.

Seeing as you are hoping to change the floor finish anyway, it would not be a major job to break out alittle area and see what the story is. Its quite possibly just where the screed meets the subfloor under it that is allowing a tiny vibration to cause the clunk sound.
Even if you were to take up 5 or 6 sq.m. of floor screed and replace it, it would be a minor job, you could possibly do it in a day. If there is no plumbing in that area, it would be even easier

Thanks for replying.

The skirting has been removed already so i can't check that way.
I'm hoping not to have to rip up the floor & replace it.

The house is 30 years old & every time i try to upgrade it i run into problems not of my making, eg
1. Under the stairs the floor is not finished & is actually a couple of inches below the level of the rest of the floor & the walls under the stairs aren't plastered;
2. Radiator backets are plastered over so replacing them knocks lumps off the plaster.
3. Mains water feed pipe (hydra?) is more oval shaped than round and requires a lot of careful filing to fit an olive on it.
4. Upstairs central heating manifold has a stud wall built over it.
5. The pipes from that manifold don't feed the rads in any sensible order.
I could go on & on.

You can understand my reluctance to dig because if i start digging i could bring more trouble on myself.

heinbloed

There are cameras available for the purpose. A 20mm borehole at the suspicious spot and a movie on CD.

Soil Mechanic

Hello Bagels,

first off , IF your slope is unstable then tiling your hallway floor will be the least of your worries...............

As your house is over 30 years old, then any differential settlement would have occured by now, save for longterm consolidation of your sub-soils.
Q. do you know what foundations your house is built on?
Piles/Raft/Strip etc. ?

The only thing that might be concerning is this slope you are on?
You will get some creep - the question is how much and has it happened suddenly? (N.B. over the past few years/months....)


More information is needed, and as always, advice would be to ultimately seek a professional opinion.
Lifting some floor material, or alternatively (and more cleanly...) having a fellow with a conrete core drill do one or a number of holes/cores to have a look might not be a bad idea.

Seek out more information first. Then see about solutions.

SM

bagels

Thanks for the advice everybody