What's happening? House movement content

We live in a house that’s approx. 15 years old. It’s an end-of-terrace semi town house, built on the land of a large manor which was torn down due to subsidence (eventually) being found (the owner waited for years letting it rot by all accounts until he had a reasonable reason to tear it down and ‘develop’ the land).

The floors have always been a little off-flat (lean toward neighbour’s house) In the time we’ve lived here (three years), but we first noticed something odd when the metal garden gate stopped shutting properly – either the wall the metal support and hinge is attached to had shifted, or the house had. Then we noticed the front door shifts during colder months and catches on the lower sill. Then the other day we found our bedroom door doesn’t shut properly, but scrapes against the top of the door frame – something that’s not been a problem before. It should also be added that various houses in the mews have also had plumbing issues – apparently the builder used a trainee to cut costs, which could suggest something about the quality of the construction.

For what it’s worth, we’re next to a wood and the back garden drains very badly, to the extent that the area that doesn’t get any sun is only ever dry during mid-summer and actually had marsh grass growing in it over spring.

We figure the house is shifting depending on the seasons and moisture in the ground – anyone care to proffer a more educated opinion?

Not unheard of for end terrace houses to go sliding off down hills.

to an extent all houses shift with the seasons.

how ever it depends on the extent of movement your seeing.

What part of the UK are you in? Some ground is sensitive to moisture content changes, plus you’ll have general thermal movement of the building. Is there any cracking in external pointing/render?

For what it’s worth, we’re next to a wood and the back garden drains very badly, to the extent that the area that doesn’t get any sun is only ever dry during mid-summer and actually had marsh grass growing in it over spring.

Is it on clay?

What part of the UK are you in? Some ground is sensitive to moisture content changes, plus you’ll have general thermal movement of the building. Is there any cracking in external pointing/render?

Isle of Wight, about 30m above sea level. There are some cracks in rendering, but nothing huge.

No sightings of great carnivorous worms either, but I imagine if they have any sense they’ll only appear at night…

Edit: yes, on clay. I suspect there’s a shed load of building debris under the garden too, but then I thought that’d actually help with drainage.

Could be volume change in the clay related to the trees, though the structural engineer should have accounted for this in their foundation design. I would have a word with the developer about it.

Do you know what trees are near you and how far away they are?

Isle of Wight, about 30m above sea level.

Ahhhhhhhh.
There’s a reason we take bus loads of civil/structral engineering students there every year to look at ground movement, damage to properties (and places where there used to be properties), landslips etc. Mainly east and south sides of the island, but I don’t know much about the west.
Also have some involvement in a long term monitoring projects on the landslips at the southern tip.

The only real way to know what is going on is to get in a structural engineer or building surveyor – in your case I’d be seeking someone local as they’ll probably have built up experience of what’s going on in the area over the last few years.
If it’s serious, they might recommend some ongoing monitoring or regular inspections to keep tabs on what’s happening. Hopefully what you’re seeing is very localised and can be explained away by a combination of seasonal effects (extended dry period recently), close tolerances on doors frames etc with minor rectification works and not part of a wider ground movement on the island.

Structural engineer and insurance, potentially.

I would have a word with the developer about it.

😆

Not sure s/he’ll be too interested, assuming I could track him/her down.

Do you know what trees are near you and how far away they are?

A mix, all deciduous. The wood is a former Victorian park that’s been left to do its own thing; nearest tree to the house is an old oak that’s been heavily trimmed and is about 5-6m from the house. The wood proper starts about 10m from the side of the house, but is all relatively young. There are some bigger, older trees (variations on oaks, if I were to hazard a guess) and the nearest (other than the garden) is about 8m from the back of the house; however there’s only a few trees of substantial size nearby, the rest are all fairly young, tall and thin, and include some sycamores.

Ahhhhhhhh.
There’s a reason we take bus loads of civil/structral engineering students there every year to look at ground movement, damage to properties (and places where there used to be properties), landslips etc. Mainly east and south sides of the island, but I don’t know much about the west.
Also have some involvement in a long term monitoring projects on the landslips at the southern tip.

We’re in Ryde, so on the more stable side of the island! I imagine you head to Ventnor quite a bit?

Sounds like it’s worth speaking to an engineer/surveyor regardless. Surprised it didn’t feature in the survey as we went for a more in-depth one on purchase, if memory serves.

+1 to ahhhhhh

Do you know if you’re in a chalk area of the island as well? To be honest, unless particularly large cracks are opening up you’ll probably be ok. Issues may be rain ingress through render cracking, and potential for leaking drains (which will just exacerbate the problem). Worst case scenario is void formation in underlying chalk. I think I’d speak to an experienced local surveyor as soon as you can, will give you peace of mind if nothing else.

Blue Slipper aka Gault Clay?

import: monitoring of undercliff drive? I did some GI there back in 2001 or 2002, just neqr the photo that was on QJEGH…..

edit double post

Do you know if you’re in a chalk area of the island as well?

It’s all chalk… 😉

We’re on a ‘marls formation’, if that means anything?

Yes, I’d get a surveyor in.

If your ground is stable normally it could be all sorts of things, wet ground, normal fluctuations (a max 25mm with safety factor of 3 is what we allow for in our ground investigation reports), but the mature trees could be a problem. Sadly I don’t have the building near trees guidance to hand but it could be that the trees are causing the clay to change volume. Any decent structural engineer will have designed to allow for this.

Sounds a likely candidate is differential settlement due to poorly constructed foundations… but only guessing as you indicated other poor workmanship. Under pinning normally solves this. Normal settlement of 20 to 25mm is no problem. I would wait a few months and see if the doors stop jamming. Gault clay is renowned for slope instability and shrink swell. Most important is don’t stress, these things can seem really bad but many buildings settle over time due to soil consolidation. Speak to local civil or geotechnical consultancy (my line of work).

What MoreCashThanDash says about insurance. Notify them immediately assuming you are covered for this. They will probably appoint an engineer. If you employ your own make sure its a structural engineer not a surveyor. You will be outside of something like an NHBC warranty as they are usually 10 years.

Just an add on.. if your concerned then get a spade and dig a small hole right next to the side of the house. Small hole and go to the bottom of the foundation. Your looking for 800mm plus from ground level as a minimum foundation on clays.

Bear in mind also that we’ve had quite warm humid weather this summer and wood absorbs moisture to equalise with the atmosphere, then swells.

import: monitoring of undercliff drive? I did some GI there back in 2001 or 2002, just neqr the photo that was on QJEGH…..

One of the sites we visit, though I don’t do any active monitoring there now. Some of my colleagues have been collecting data around there for 40+ years and have watched entire streets (in Ventnor etc) crumble away over time.
Currently the more serious long-term stuff we do around St. Catherine’s Point, concentrated on the land slips there.

+1 to coconut – I’d be hopeful that it’s a localised problem and therefore, containable or rectifiable without major disruption to the house.

Great, thanks all. Got a few calls to make. 🙂