Subsidence

[MikeFleming]

Hi, I am considering buying a 1979 house with subsidence and wanted some advice to see if it worth pursuing and paying for a SE report. The left hand gable wall is bulging and there is a vertical crack in this. The centre of the bulging seems to be below floor level and the vertical crack ends at internal floor height.

The other problem is the internal floor is dipping by about 30-40 mm. This is shown on the floorplan shaded green.

Untitled

• MikeFleming
• 29 Jun 2012
• 1

Untitled

• MikeFleming
• 29 Jun 2012
• 1

The door is a little skewed in its frame (about 5mm) where the floor is dipped. There are no other obvious problems.

The vendors insurance will not cover this, as remediation was previously done which they say was sub standard. They estimate 40-80k to correct this. I have not seen the reports so I don't know if movement has ceased.

So my questions are, is the cost estimated too high. I am thinking that the SE would say a high cost to cover himself, and because it was going to get done under insurance? Or does the difference in ground level between the front and left side (I guess its about 1 meter) make it much more involved than normal underpinning?

I am downsizing, so wont be needing a mortgage, and don't care much for insurance, so would prefer to keep money aside in case further work needed doing.

Thanks for the advice.

Mike

Untitled

• MikeFleming
• 30 Jun 2012
• 1

 

[^woody^]

I can't see how this crack and bulge can be subsidence. More likely to be one or a combination of one or several other causes

 

[MikeFleming]

what might it be?

 

[joe-90]

Woody's the expert but I'm thinking it might be 'heave' where a clay soil expands due to the wetter weather we seem to get. Do a Google.

Are you getting the house at least 40% below market value?

 

[^woody^]

Bulging in a case like this would perhaps be an issue with the floor, the fill (sulphates) or insufficient ties

If the size of that vertical crack is indicative, then it would seem to be too small to be movement of the elevation. It difficult without seeing it

But subsidence would be further down the list of possibilities, but that's not to say whatever causing it would not be just as costly but I just cant imagine anywhere near £40k

 

[noseall]

Is there any history of sulphate attack in the area?

Is the house located in a coal mining area?

An entire estate near to where i live (N.C.B. houses) were built using red ash infill in the floor void, leaving many of the houses having to have the entire ground floor dug out complete with infill. The estate was built on a hill meaning some of the homes had as much as 1.8m of infill!

However, i do find the location of the bulge a bit odd. My guess is, if it were sulphate infill problems, then the floor would bulge before the wall?

I suppose the weakness due to the dpc junction may allow for ease of slippage and mebbe a little rotation?

 

[MikeFleming]

Thanks for the responses. I am going to try and get a copy of the previous report.

The other thing about this is that an attempt was made to rectify problems previously, and that's the reason the insurance aren't paying out now, which makes it more concerning.

To clarify, the internal floor is dipping, not bulging, and this is on the front of the house, as indicated by the green shading. Does this make a difference?

 

[^woody^]

If the floor dip corresponds to the wall bulge, then there could be a link - either fill pushing out the wall, or the wall moved out and allowed the fill to drop. And then you'll need to know what has caused that - leaky drains, settlement of the fill, pressure on the wall, sulphates etc

You really need to get a proper survey which will give a likely cause, and then you will know potential costs

 

[MikeFleming]

I got the survey. There are two main problems. One is that the subfloor is failing due probably to bad fill. They engineers view is that it should be dug out and replaced with a suspended floor.

The other problem is that the flank wall below floor level is bowing as it is not strong enough for the weight. The ground level by this wall is about 1.6 meters below floor level. The think is you have to walk down by the side of the house, only to have to walk back up again at the end of the house. Bring e.g. a lawnmover down this path would be tricky. I use a motorbike and store this in the yard, I couldn’t get this round the back of this house. So I wonder, would it be possible to strengthen this wall from the outside, and at the same time make the path a level surface all the way around the house.

Would this be possible? If so, what form would it take, I was thinking of shuttering the width of the path, and concreting it whilst tying it into the wall somehow, this might be a little extreme, so maybe this half the width and make the rest of with blocks?

 

[^woody^]

For bad fill, you wont know what its like until its excavated. An engineer will always recommend complete replacement of the fill, and whilst that may be prudent, it may not be necessary.

Another option may be something like www.uretek.co.uk

The wall can be rebuilt in a section or, if the floor is excavated, some means of load dispersal can be put up against the wall before backfilling. It may even be just a case of lack of filled cavity. Either way, its not a major job if the foundations are OK.

External support or buttressing is possible, bit I can't see why it would be needed instead of just some limited rebuilding

 

[MikeFleming]

Thanks again Woody.

I had a read about the Uretek system, looks great, I wonder how it would work with the weak gable wall though, perhaps it could be done if that was sorted first.