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Groundwork & Foundations

Concrete floor sunken

Hi,I am lookin for any info as why a original kitchen concrete floor has sunken,
house is aprox 1930-1940,ground floor kitchen,
floor has sloped away from centre of kitchen ,the areas about 1.5sqm and drops 100mm or more towards exterior wall,
There is a soil pipe an waste water drain outside to where it has dropped,this has happened over a period of 5 to 10 years.
Would this be an ash floor & quarry tiles ? It is covered with lino at the moment.
Could there be an undergound pipe leaking outside causing this over many years and how would I go about Replacing the floor if I rectified the cause of the problem?
Regard Mark

Thanks for the information guys,luckily there is no cracking on building so it looks like a collapsed drain,concete path outside is dipping towards the house too so 1st thing i will do is get the spade out and dig down carefully and investigate the drain and pipes and see if i find a leak.
Appreciate your time and advice.
Regards Mark

3 Answers from MyBuilder Groundworkers

Best Answer

100mm drop in your floor over a 1.5 square metres sounds quite serious.
I would say, as you have suggested that you have a collapsed drain, so order of work.
Rip up the existing floor, dig down and find your drains, you are going to have to have these repaired first.
Then excavate down from your finish floor to allow for 75mm floor screed over 100mm concrete slab over visqueen membrane, allow for 75mm of floor insulation on a blinded base of about 150mm good clean hardcore or type 1 mot, hardcore needs a compactor plate on it.
It all sounds easy to a builder, but I wouldnt reccomend you do it, the drainage problem isnt really a diy project.
Post the job on this site and get a good tradesmen, if you want to save a bit of money, do all the digging out.


Answered 6th Apr 2011

Hi Mark,
Number of ways to go, mostly a process of elimination.
Have a camera inspection done on the drains, I just had one where the clay drain had dropped from it's joint onto the manhole and although the drain was still running a large void had appearred around the break causing the concrete path to drop. if thats the case. Repair the drain and look at either lifting half the sunken concrete floor or all of it and putting in a new sub floor and damp proof membrane.
The main thing that concerns me is that your floor should be not far away from the inside edge of the foudations of the wall. If there is sub floor subsidence, then it will also be plausible to think that the foundation is being washed away or weakened.
Are there any signs of movement near that corner, cracks large or small, near any window lintels or doors?
Is there any cracks in the brick work further back where the kitchen joins the house?
If there are then you have some serious structural problems which will only be solved by underpining (new foundations) If you are in doubt have a structural engineer do a survey.
Route 1 get the camera survey done then take it from there. If drains are intact.
break up the concrete inside until you are at least halfway back to the level area, then investigate the cause and remedy.
Good luck . Regards Mark


Answered 6th Apr 2011

it sounds like the base for the concrete has disapered or there is a leak like you say and over the years it has sunk,the only way is to dig up the concreat so you can see underneeth. you really need a builder to look at it ,hope this helps


Answered 6th Apr 2011

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