Sagging floor and cracks

19 Aug 2011
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United Kingdom

We moved into a 1930s semi in May. Homebuyer survey carried out in February reported no problems with cracks etc.

The house has an extension which was built over 20 years ago. I've noticed, in the last two months, that the floor (which is LVT over concrete) has started to sag in one particular place in the kitchen, which is approximately where the extension is. It's dropped around 1cm at the lowest, and the sagging area is about 1 meter in width. The floor isn't sagging anywhere else that I can see.

I'm aware that the long drought over the summer has resulted in a lot of subsidence claims, and I'm worried that this might be what it is. There are no cracks downstairs, but I have noticed vertical cracks around the doors upstairs and there are a few horizontal cracks in the old part of the house. One door has started sticking a bit (the one nearest the extension).

They are all hairline cracks and none are diagonal, although there is one in the landing which goes around where the RSJ must be - where the old house meets the new house. The cracks inside the bedrooms have appeared since the summer, but it's impossible to know whether the ones in the landing are new, as the whole area was covered in woodchip wallpaper, which we have removed and had the walls replastered in July.

There is also a vertical crack in the render outside where the old house meets the new house.

Does this sound like subsidence? The only other thing to mention is that we had a new kitchen installed, and a new dishwasher put in, and the sagging floor is quite close to it. Could it be leaking?

Thank you.
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Gazelle1, good evening.

If possible some investigations into a water leak or leaking underground drain would be IMO best place to start?

Odd sounding question but? can you hear any hissing sound [an indication of a water leak in the incoming water main?]

Are there any areas of standing water externally? any hint of blocked drains?

OK the Insurance Industry are in the middle of a massive so called "Surge" in insurance Subs claims occasioned as you say by a more than warm but especially dry summer, first dry summer in several years.

It is not all that unusual to get differential settlement between new and old structures.

As for "hairline cracking" in newly skimmed walls is not altogether unheard of, in fact relatively common.

Hi Ken,

Thank you very much for replying. We can't hear any hissing, and don't have standing water or evidence of blocked drains. The underground drain survey sounds like a good starting point though.

The cracks in the bedrooms (around the doors) seem to have appeared since the summer, which makes me think there must have been some movement - it's only the landing which has been replastered. No cracks at all downstairs though - is that unusual?

Gazelle1, good evening again.

If you put your ear to the cold tap you may hear a leak in the form of hissing? if not then that tends to rule out a mains water incoming leak underground.

As for the new dishwasher? worth getting down on your hands and knees with a bright torch to see if there are any indications of water leaking from the device?

You mention " cracks around the upper floor doors?" are the cracks vertical from the head of the door to the ceiling? the rational is that in some "older" forms of construction, the timber of the door casings were full height floor to ceiling?

locating a possible underground drain leak would take a CCTV Survey to be sure about the state of the drains, if indeed there are drains in the immediate area.

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Hi Ken,

Thank you for replying again. No hissing sound or any evidence of leaks weirdly. We can get this checked out though.

The cracks around the doors go straight from the top of the door frame to the coving. They are only on the upstairs doors and have appeared since the summer. So it does feel like there might have been at least some movement in the house.

Thank you

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