Foundation checking / extensions on potential property - bit stressed

[OneArepa]

It’s me getting a bit stressed. Haven’t seen anything to indicate the house is stressed…

Have had an offer accepted on a property that has already been extended at the rear on the ground floor only. We’d want to extend the first floor at the rear.

If we have to pull down the existing extension, dig deeper footings to support two storeys and start from scratch, the cost potentially becomes an issue.

There’s no historical planning application showing the date of the original extension so may have been a PD job. Historical satellite pics indicate pre-1999.

Footings are going to be too shallow, aren’t they? What are our options to be sure - is there a level of survey that could check the existing footings? Have we got any other way of ascertaining this before completion?

Sorry if I’m missing something obvious. Bit sick, quite stressed and v tired.

the only way to be sure is to dig a hole at the side of the house to see how deep the foundations are . Here’s a picture of the foundations on our house there are 300mm of concrete in , it’s a 2 story house with no structural problems , was built in 1979. There is no way that would meet regulations today but then it was fine . You need to dig and go from there.

Ooopps. Forgot picture, obviously a small hole would be fine

Thanks. I’d go over there with tools myself if they’d let me 😂 but short of that option, is there perhaps a way a surveyor could do this - is it a ‘thing’, ever?

I’m not sure anyone could be 100% sure how deep they are without actually uncovering them . The only way it could be agreed is if it was a recent extension and it had passed building regs and they had some sort of plans that they worked to .

They would have needed building regs for an extension irrespective of planning.
Get your solicitor to request the approval notice and completion cert (there may not be a cc if it's really old).
A single storey extension may not have adequate foundations for a first floor, but the only way you'll know is a trial hole.
You probably won't have to demolish it. At worst you'd need to underpin the existing founds.

It would be cheaper to buy a bigger house right now. Extension costs are mega.

Tizer try telling that to the market round here…

hesbeing brill. Will do that, thanks.

I think I’m panicking but I’d sleep better with some answers and patience isn’t my forte. We’ve had some very worst-case qualified numbers and we could still do it, it just affects whether we can blitz the rest of the list with the equity. Not maxing out on mortgage available as trying to be somewhat prudent so it’s where wants become needs etc.

@hesbeingabitofadick also, by ‘really old’ how old might we be talking?

@OneArepa
Have you got quotes? Any idea of costs? I live in an expensive area but paying extra for en already extended house, then not knowing what you can do and what the associated costs are, doesn’t seem sensible to me.

Tizer we have had some worst case numbers from two builders using drawings for this house (which are existing) and two of the same original layout which have had the same extension done. Short of going round to a house we don’t own with an architect, structural engineer and builder right now, I’m sure quite how we are expected to get actual quotes. As mentioned we are therefore working on a worst-case basis, which is not being able to do everything we would like. Also as mentioned, we are sensible enough to not max out (in any climate, let alone this one).

I am very tired, quite generally stressed, and doing as much research of all types as is feasible in our current position. It is not the first house we have extended, only we are aware that costs have risen exponentially. Trying to ascertain as best we can how much we can do in advance of buying the property is exactly what we are doing.

We built over a garage without the correct level for foundations had to strengthen with a column and lots of steels. Building regs and a structural surveyor.

Completion certs were introduced in the 90s (we think).
Anything from the certainly 80s shouldn't have one.

As tootired has mentioned building over a garage...is the existing extension a garage or a room? If it's a garage and single skin brickwork, it really would be easier to knock it down and start again.

hesbeing thank you - that’s helpful to know. Existing extension is a room, so that’s one plus.

tootired I guess underpinning wasn’t an option?

The problem with building above the garage wouldn't have been the founds. The walls may not have been thick enough to support the first floor double skin of blockwork/brickwork then roof above. This can be solved with steelwork, but relies upon good foundations.

sorry, meant "wouldn't necessarily".
And lots of things can be worked around with a structural engineer - I think that's who you need advice from rather than a builder, although you may have to wait until the house is yours.

That makes sense - thanks again.

@OneArepa we're hoping to do something similar and as others have said, it would require a test pit as part of the building control process (same as new foundations would require a sign off). If not good, the existing building would need underpinning not knocking down and starting again (assuming you'd be building onto a double skinned wall). Quote we've had for worst case underpinning is roughly 10k for about 14 linear meters of wall if that helps.

Out of interest, would you be willing to share the rough costs you've had for the second storey extension? We're getting wildly different estimates where we are

DH is a structural engineer. The weight of buildings is supported by foundations. The weight goes via the walls into the foundations /ground. Steel frames don’t just sit on the ground. Single thickness walls won’t take the weight into the ground effectively. It’s important to ensure the building can be used for what you want. There isn’t an answer without an engineer looking at it. You must know what the foundations are and how the extension is built. You can find out the latter but the foundations are more problematic.

No one ever mentioned underpinning. We had a builder planning permission building regs and a structural engineer. It was a single skinned garage and we built a bedroom on top. Builder dug down in the garage and created a column that strengthened the outside wall inside wall was double skinned as that's the house.

@TizerorFizz , I’m not sure if that was at me but I do grasp what foundations are for and why. My original question was simply about if there will be any feasible options to investigate existing founds before completing on the purchase so we know more about what we’re working with and can plan budgets accordingly.

@bumbledeedum good luck 🤞 we had to underpin on the first extension we did and those numbers sound in line with what we had to deal with. Ours is a bit complicated but we’re looking at £85-95k ready to paint and fit kitchen/bathrooms.

@OneArepa Only if you are allied to dig a trial pit. Or you can get accurate drawings. You might not trust them though.

I was responding to whoever was talking about beams and single brick walls. Beams are not a substitute for foundations. That’s all.

Thanks. Sorry if arsey. Overtired and stressed with non-house things.

We sold a house last year. One of the prospective buyers wanted to do quite a bit of work, and asked for another viewing with their builder, structural engineer etc. That was totally reasonable.

If part of the reason for buying the house is a 2nd floor extension then I think it is perfectly reasonable to ask for a surveyor in the first instance or an engineer to look at it & if they think it might need pits for viewing etc then possibly you can either take a view on worst case & hope better or just pass. If someone wants the house quickly & does not care about the 2nd floor extension then maybe in a better place but if I were the vendor I'd be happy to have someone come round with qualified people to have a gander.

Best of luck

We’re currently buying (or hoping too) a house with structural issues (main body of house is fine). Garage wall is single skin so is cracking, fairly easy fix with helibars. The utility (a single story small extension done in early 90s) is slipping away from house, most likely due to poor foundations. Our mortgage provider insisted on a structural engineers report and builders cost for repair (& our commitment to fix) before they’d consider mortgaging the property so that’s what we’ve had to do. We’re also getting a drain survey this week.

Our builder said we’d need to dig a hole to check foundations, but also said that it might be better to pull it down and rebuild than repair. Given it’s only a utility we’ll take the risk as I don’t think it’s reasonable to dig inspection holes in our case, but if it’s an extension that’s more part of the house I would.

We are under pressure to complete by mid-Nov otherwise our buyers lose their mortgage deal and can’t afford the higher rates. It’s added another 3 weeks to the process with the time it’s taken to find people to visit and quote on work, but we need all the facts before we proceed. If the drains turn out to be knackered we’ll probably pull out and rent for a bit instead.

Ask your estate agents for contacts, ours had a list of people they’d used in past for similar issues. Good luck sorting it and if it’s too much risk, I’d walk away. Better to lose a few thousand in fees, surveys etc than buy a money pit.