Bulge in concrete Kitchen floor

Postby claireandliam » Mon Dec 17, 2007 5:53 pm

Hi, we are buying our first house, a 1930's semi detached terrace. The kitchen is incredibly dated and not been updated since the house was built, and towards the back of the kitchen extension, in the middle of the floor, there is a crack in the lino, underwhich is a lump of concrete. We have had various opinions, however, none of which are able to suggest to us whether this is going to be a huge long term problem. the rest of the house is fine, however, if this could suggest subsidence we are reluctant to proceed with the purchase. Has anyone had a similar problem? Does anyone know whether if we were to rip out all of the extension and kitchen and replace there would be a problem reselling if there was subsidence? Thank you
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Simply Build It

Postby john9159 » Mon Dec 24, 2007 11:18 pm

If you had subsidence this would have been identified in the survey.
You can look at the outside of the house for cracks in the brickwork which will appear stepped, usually with a noticable gap. This is referred to as settlement and not subsidence and does not, or should not, cause a bulge in the concrete floor, which has probably been there since the house was built.
Given the age of the house, there may not be a DPC under the floor, even if there is, this will be some way beneath the surface so grinding away the affected area is safe to do.
The down side is that this will lead to a tremendous amount of dust if done dry and will probably take an age given the hardness of the concrete.
Have you considered a floating timber floor? This will involve raising the level of the floor but can give an improved appearance, given the right type of house.
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Postby htg engineer » Tue Jan 01, 2008 1:55 pm

Check with your surveyor, local authority and neighbours. For any floor heave problems in the area.

Sulphur attacks on concrete floors can be a very serious problem and cause problems with the whole building structure.

You tend to get this sort of problem with houses built in mining areas. Bore hole tests can be carried out, to determine whether there is high amounts of sulphur present.

If only a small are it can sometimes be dug out, sealed and the floor re-laid, if a bigger problem all concrete floors would have to come up. A DPC instralled and the floors re-laid. Not cheap.

It's best to find out what it is before purchasing - even if just for peace of mind.
htg engineer
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Postby miketr » Sat Jan 26, 2008 8:43 pm

Hi during the 30s and 60s it was common to use power station ash in concrete mix. This when it gets damp can be prone to sulphate attack this causes expansion and a breakdown of the concrete. The cure is replacement dig the old concrete and replace with new concrete protected by a damp course membrane.
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