Porch subsiding a bit

tanith

Hi , not sure this is right place ......... we have a small brick built porch to the front of the house that was added on by the previous owner. It was well built and we have had no problems till this year.. I noticed the other day that we have lots of internal cracks appearing around the windows and down the corners... if I look outside there is a very fine crack where the brickwork joins the original house too.

I guess this is caused by the exceptionally dry weather and shrinkage in the clay(we live in West London) , will this cracking settle down when the damper weather comes and if I fill in the cracks and repaint will that repair the damage or is this going to be ongoing and getting worse?

My son in law suggested we dig down and support the foundations with more concrete before it gets any worse , is this a good idea?

bluekp

I would contact your buildings insurer - they will normally send an engineer out to assess the damage and if it warrants it they will carry out a ground investigation, take some samples and analyse them to see if it is subsidence causing the damage.

If it is then your policy should cover any repairs.

If you do live in an area susceptible to subsidence then even if you fill the cracks for now, come the next dry period you will more than likely see the same thing happen again.

Hope this helps.

tanith

Thanks Bluekp , I know we are on clay and my brother who lives a few hundred yards away had a problem with subsidence a few years ago but this proved to be 3 large willow trees growing in the park at the bottom of his garden.....

I will get in touch with the insurers to find out how we stand, and I am sure we have a big excess on our buildings insurance so for a small thing like a porch maybe we would have to bear the cost... just hope its only the porch thats affected... there are no signs at all in the main house thank goodness... one thing that worries me is how we would stand as the porch is an add on and not built with the main house

courtjester

tanith,

Sounds like differential movement of the porch foundation - almost certainly built with shallower foundations than the main house which is standing on deeper ground unaffected by the surface soil shrinkage (in itself due to soil extraction exacerbated by dry weather).

If this is due to proximity of trees, then reduction of the size of the tree is usually the remedy and it may not be necessary to underpin the porch foundation - if you wait until a wetter season (Winter), the cracking may well close up which is a sure indication (soil shrinkage due to moisture loss).

If there are no trees, it could be a drain or water pipe leakage problem - washing out the fine particles of soil below the foundation - this will only get worse unless the drain /pipe is repaired.

Willow trees are about the worst culprits for draining soil of moisture so you don't want these anywhere near a building.

You almost certainly need professional advice and some investigations before considering the best method of remedy - contacting your building insurers is the first step. You will be responsible for the first £1000-£1500 of professional fees which is the standard subsidence excess. As the porch is part of the building, it doesn't matter that this was 'added-on', it's still covered subject to the fact that it might be cheaper to knock it down and rebuild with deeper foundations than try to repair, but it is imperative that you establish the cause before taking any action as you could make things worse.

If the cracking is minor at present (2mm or less) this may restore once the drought conditions improve and you could just live with it if it doesn't get any worse and there is no evidence that the main house wall is affected, but it's worth advising your insurers to get their opinion as this costs you nothing.