Request for advice - engineering/surveying types

pinkbikini

I think there are some engineering/surveying people on here, or at least people who know about these areas re. residential buildings.

I need to get an inspection of the side wall to a rear extension, which has a diagonal crack (following the brickwork mortar) rising up the side. It's generally not too wide (although maybe 2-3mm at the bottom) and narrows towards the top. No visible cracking inside the building. Extension is 12yrs old. Low garden retaining wall tied into edge of extension wall (garden wall on much smaller foundations), crack starts level with top of retaining wall where it joins the extension wall and rises back into extension wall.

House built on London clay. Slightly sloping ground, about 15m upslope our neighbours removed a large (10m+) Sycamore tree about 6yrs ago.

First noticed the crack on corner edge of wall about 4yrs ago, but very small and didn't realise it ran along the side - we can only see the side if we go round to neighbours garden and peer over the fence (they saw it when up on a ladder cleaning a window).

I suspect it might be heave (based on a quick search and the nature of the crack) but want to get an inspection. But what sort of person am I looking for though - structural engineer, some type of surveyor, building firm, of something other? I'm in London SW19 if that helps.

Thanks in advance for any info.

Ben6899

Hi mate. Sounds like classic subsidence (possibly caused by moisture content change, following removal of the tree).

You need a Structural Engineer. Make sure they're kosher (Chartered or Fellow Member of IStructE; not some bloke in a van who "knows bricks").

rjsterry

From what you've written I'd have thought a structural engineer would be best placed to advise on possible causes of movement. PM me if you want a name of one.

Pross

Yep, one for a structural engineer. Do the cracks open in summer and close in winter or have they gradually increased? It could be subsidence from the shrinkage as the soil dries out or possibly heave from the tree being removed but if it was 15m away it would be just outside the range where foundation depths would be stepped up even for high shrinkage soils and high water demand trees (a sycamore is moderate water demand). According to the NHBC calculator the foundations would only need to be 1m deep.

pinkbikini

Thanks all, useful info, esp. knowing what type of surveyor is required. Now getting some quotes.

darkhairedlord

Put some cladding on and forget about it.

monkimark

Might be worth sticking a telltale across the crack so you can monitor if it is growing.
Something like this, it's essentially two plastic rulers that measure the change in crack width. Useful to have that info for the engineers, although no doubt they would bring one themselves as part of the survey.

https://www.ebay.co.uk/itm/RECON-SURVEY-TELL-TALE-WALL-CRACK-MONITOR-STANDARD-5-49-vat-/124655362644?_trksid=p2349624.m46890.l49286

briantrumpet

Thanks all. This has prompted me to look up a local structural engineer with specialism in cob (there is one, who was involved on the Grand Designs massive cob house), as my old house's front wall has moved a bit over the past 29 years... I'm thinking about a project on the house next summer, so would be good to check out the structure first in good time. I prefer that it didn't end up in the road.