Any structural engineers about please? Cracks following extension...

[Arghmetoes]

Very grateful for any opinions as DH is driving me insane very worried.

We had an extension built over two years ago. Used a great builder, very experienced. We copied a plan used elsewhere on our estate - room above the garage, kitchen extended into the garden. Work was inspected, signed off, had a structural engineer out to approve everything. Additionally, when DH bought the house new (20 years ago) he asked about the garage foundations and the builders assured him they'd made passive provision for another storey on top.

We immediately had cracks appear where the house settled around, e.g. the new steel beam. I was expecting this, DH wasn't, but the builder reassured him (they were still building at that point).

Two years on and we are still getting random hairline cracks appear everywhere. DH is now convinced that the garage foundations aren't strong enough and it's falling sideways and taking the side of the house with it. Every day he asks me to inspect some new crack that he's spotted (usually one that has been there for a while), or opine on whether an old one is getting longer or wider.

From my perspective: none of the cracks are wider than a few mm, most are hairline and less than 1mm thick; we've had the heating on a lot more (and at a higher temp) due to WFH; most of the cracks appeared within the first 12 months after the build; extensive Googling says don't worry unless the cracks are very wide; I've seen subsidence on properties before and that included wide cracks in the exterior wall that you could fit fingers or coins into and this isn't it; none of the other houses on the estate seem to have a problem (and thanks to lockdown we walk past them every day).

From DH perspective: none of these cracks appeared until after the extension; they're all clustered around the stairs / old exterior wall / new room above the garage / new kitchen roof (which has a massive glass lantern in it); we are still getting new cracks over two years later.

I can't seem to reason with him - and this anxiety predates the pandemic, although it's definitely getting worse. It's got to the stage that I'm tempted to pay for a structural engineer to have a look and put his mind at rest even though I think it will be a massive waste of money.

Is there anyone with experience of this stuff (structural, not relationships!) who can advise please? Should I be worried about this?

We had a similar problem, contacted our insurers and they monitored the cracks for a year. If there is a problem they will find it. Your builders will have their own insurance and your insurers will contact them if necessary. In our case it was a problem with the mains drainage and the water company fixed it.

Can't advise but we had an extension about 4years ago now and we have quite a few large hairline cracks too. They look like someone has drawn pencil lines over the plaster. I think hope the cracks would appear "open" if there was a genuine problem. I think there's always a bit of settlement after an extension, loads change, the house kind of adjusts?

It's usual for a new build to take a couple of years to totally dry out and settle. Hairline cracks are normally nothing to worry about. As a simple test put some tape horizontally over the cracks - if the tape falls off then you know there is active movement

Pictures might help ? Are there any cracks on the outside ? Hairline cracks are common on newly build houses/ extensions especially if it was very wet/ damp when they were built.

If there are no cracks on the outside then I’d say the house is not going anywhere.

Thanks very much for your replies. There are definitely no cracks in the outside walls, or even the old outside wall (that is now an internal wall). They all look like hairline plaster cracks, apart from where there is woodwork next to brick, e.g. windowsills, doorframes and the stair strings / shoes. Those cracks are more like a few mm - I managed to fit a very thin knife into those the other day.

Any pics available?

My DH is FIStructE and FICE but as I’ve been married to him for 40 years and it’s not me who’s qualified I’m assuming you don’t want an opinion?

When you got approval for the building regulations, were you asked to expose the foundations of the existing building that you put the second storey on? We had to dig out each corner which given the foundations were 2m deep it was hard work

Small cracks hairline cracks very common for several years, it’s really annoying as it spoils the new decoration that you do after building work.
But it’s probably nothing serious if you did everything properly, had it checked, signed off and had a good builder.
If you are really worried it may be worth getting it checked just for your peace of mind.

Two questions:

1. What's the subsoil? (Clay is notorious for settling - about 50% of the settling takes place in the first two years, but the remaining 50% can take up to a century!) Extensions will settle and will form hairline cracks.

2. How was the extension attached to the rest of the house? I'm hoping the extension was free-standing, with a seal of some sort to ensure water-tightness. If (as some cowboy builders sometimes do), they've keyed the new brickwork into the old brickwork, you could be in trouble (because the old house will effectively have done all its settling, whereas the new extension will be in the process of compressing the subsoil - which is why you don't physically attach them one to the other, you just put a watertight/weathertight seal between the two bits).

(Based on what my DDad, who's a structural engineer with decades of experience, has said to me while looking round prospective house purchases with me.)

Sounds like you need to get someone in to do some monitoring. This could be done via a structural engineer or via your insurance (who will hike up your premium I'm sure). We had this as part of an insurance claim and essentially they put loads of metal markers on the cracks and some screws in the walls and come out and measure every weeks or so.

If it's subsidence you should be covered by insurance. If it's faulty workmanship you may have a battle on your hand with the builder.

@PresentingPercy

My DH is FIStructE and FICE but as I’ve been married to him for 40 years and it’s not me who’s qualified I’m assuming you don’t want an opinion?

What a strange post! Had to reread the OP looking for something rude she's said about people asking their partners, but nothing there!

Don't involve your insurers unless it's really serious - even making a phone enquiry without making a claim could push your premiums up.

What a strange post! Had to reread the OP looking for something rude she's said about people asking their partners, but nothing there!

@ItsIgginningtolooklikelockdown Glad you thought so too... I have ASD and I've been wondering what I said / what I'd misinterpreted!

@MarieG10 No, but thanks so much, you've reminded me that we had to extend the back of the garage by 1m and to do that they had to dig a bloody big trench for that bit of the foundations, so they will have seen the existing garage foundations. I'll remind DH about this.

@CaraDuneRedux That's really helpful, thank you. It's on top of an old demolished building (repurposed land). I think the natural soil is clay-ish, but they had to put 2 metre deep foundations for the kitchen because the garden is built up and was just rubble below a certain level (the garden drops away very steeply). The extension is freestanding, with a seal. I didn't know that about knitting in - I've spent the last two years wondering why they didn't do that, and now I know I worked from home for a lot of the work and was really impressed with a) how hard they worked and b) what a thorough job they seemed to be doing. For example, when the foundations for the kitchen bit went wrong (the ground just kept crumbling, the digger couldn't get to the bottom and they had to haul out the bloke with a shovel because it was too fragile), they got a bigger digger, shored it up with wood and made sure to get the cement lorry the next day (0630 on a Saturday) and worked overtime to make sure it was sorted as quickly as possible to avoid collapse.

I've taken some photos but they won't load on my phone; I'll come back and sort it out on my laptop later.

I don't want to bother the insurer, but if I can't calm DH down we may have to pay for an engineer to come out / monitor it properly ourselves. Thank you all very much for your responses, I really appreciate it

I've managed to work the photo upload (hopefully!). Two pictures showing the worst ones (on the stairs) and one showing what the rest of them look like.

To my mind, they're really small, but DH is obsessed with the house falling down I caught him looking again this morning.

@PresentingPercy

My DH is FIStructE and FICE but as I’ve been married to him for 40 years and it’s not me who’s qualified I’m assuming you don’t want an opinion?

Well that screams ‘I’m alright jack’ ‘myyyyy husbands a fellow but we’re not going to help you peasants’

Anyway, I also have those cracks around the stairs/walls. It’s a totally different situation though as our house moves with the seasons slightly and they’ll close up come summer.

They certainly don’t look like something to worry about at present. If concerned call insurance and they’ll monitor. Or monitor yourself, take some with a rule over them and the date then re assess in 1/2 months.

@Arghmetoes

To my mind, they're really small, but DH is obsessed with the house falling down I caught him looking again this morning.

Ah me too when I first noticed them, I have every sympathy

We had our house rebuilt 6 years ago.Lots of small cracks everywhere and like ones in your photo.Get a professional to put your DHs mind at rest but my husband works in construction and says its just the house settling down.The ones on your stairs...I recently had to pull up all the sealant and reseal,sand and repaint all the woodwork up our stairs due to cracks like that.It's just movement.

Seeing your photos they look like cracks we’ve had after building work, it happens a lot around where 2 different materials meet wood/new plaster.
I would get your builder back to reassure your DH, nothing worse than stressing about things.

Our house is 5 years old and we have plenty of hairline cracks. Most came after 2-3 years I would say. We recently had a surveyor here to check everything before the building warranty ran out and he didn’t find any issues. It’s purely cosmetic and the builder/architect sent somebody to replaster and repaint. They do still keep reappearing though. I’ll go and hunt some down and post some pictures.

Interestingly our neighbours (it’s a semi) had much bigger cracks on their side, where they had to knock the plaster out around the cracks and refill, replaster and repaint, but even that wasn’t thought to cause any structural problems.

To try to put your husband’s mind at ease, take some photos with a ruler next to the cracks and then compare in six months’ time.

This cracks don't look anything to worry about. One seems to be the stairs and you may have that from very slight casement movement. The rest are routine drying....we still have them after 3 years. We found we got a few at the two year point and one was from the plaster board not nailed in fully ( the surface popped as well).

If you involve your insurers, even if there is nothing wrong you will need to declare it on sale and that will frighten many off so don't do it uless you need to

Your cracks are identical to ours in our new bits. It's just shrinkage/drying out and nothing to worry about. Well, the only thing I'm worried about is finding the energy to get the Pollyfilla out and sand, fill and re-paint. One day!

Thank you all so much, that's really reassuring and he seems to have calmed down somewhat; I think I'll be bookmarking this thread to show him at frequent intervals

We’ve had much bigger cracks than that. Obviously monitor but I wouldn’t be panicking.