Extension cost

[spartanrunnergirl]

Looking at knocking down an outhouse to build a single story small extension (officially conservatory) to create a utility room/boot room type room on my house - roughly 3.5 m x 2.25 m. First quote had come back at 46k which seems v high. No experience of building though. Any thoughts on ball park figures for this size of structure?

Allow £2500 per sq m as a guide

So the quote I’ve had is £6000 per sq meter! Bit high!

Think they me taking the mick can u get another quote

We've just been quoted £84k for a very small extension - in London.

In the real world 8.75 sq m single storey extension utility/boot room should come in about 25k ... however in "London town" just think of a number and double it... they'll pay it😀

Your quote comes in at 5.25k per sq m..... should be around 3k

I can't help with prices. We added an open conservatory to 1 house and a similar sized double extension to our current one- but had other work done also.

If you went with a conservatory or orangery, depending on the size, it might fit within permitted development and not require planning. We wanted it open plan, not a door to go into the conservatory part. This meant we needed planning control to inspect, but wasn't an issue. More of a problem was various conservatory companies never hearing of this and having never removed the doors before!

an architect friend recently told me £3500 per square metre

@Elektra1 is on the money. You won’t get anything for £30,000 now. Materials are sky high. I’d go big and go once. You can get permitted development for any type of construction but size is limited. Doesn’t help with costs though.

For a 3.5m x 2.25m space (roughly 8sqm), £46k is steep; that's nearly £5,800 per square metre, which is above average even for current prices.
That said, a lot depends on what's included. Demolishing the existing outhouse, new foundations, drainage, electrics, plumbing for the utility room, and making good the existing house all add up fast. If the quote includes everything to a finished standard, it's high but not outrageous. If it excludes flooring, decoration or fittings, I'd push back.
Does the quote include structural work where the outhouse meets the existing house?
Get two more quotes against the same drawings and specification for comparison. For this size of build, I'd expect something in the £30-40k range in most areas, but London and the South East push higher.
One thing to clarify; if it's being built as a conservatory rather than a full extension, building regulations requirements differ. Make sure you know which route you're going down, as it affects costs.

Agreed.

We binned off extending because the previous owners did a 3 x3 extension.
Knocking it down going out to 4m and across would have been 70-90k in london in 2022. Once you add a kitchen and fittings it was going to be 90-120k

@Abre We have an oak framed orangery. It’s our kitchen. The foundations are 6ft. Big oak tree nearby and clay. Cheap conservatories are different but you need foundations for anything more substantial. That costs!

I think it massively depends on where you live, costs will vary. I’m in the South East (Berkshire) and we had a small kitchen extension last year (3m x 3m) and it cost £45k.

Absolutely right. Foundations often blow the budget. Clay soil plus nearby trees could mean foundations 2-3 metres deep (assuming you keep the tree). That's the kind of thing that turns a £30k job into a £45k one before you've built anything above ground. The soil conditions and tree proximity dictate foundation depth, and that dictates cost. No amount of comparing quotes helps until you establish what's actually underneath you first.
Hope that helps.
(FYI: I'm an architect in the Southeast, with plenty of experience of house extensions)

We had a similar sized extension 11 years ago and that was£30000, I was shocked at the price but we had 3 quotes all around the same.

OP we looked at similar and considered a timber garden studio type building, connected to the house by a covered walkway.
it was about £15k for a 4m x 3 m fully insulated studio, and £1k for the walkway. Would that be an option?

@Abre DH is FICE and FIStructE. I trust our foundations! Probably should have said 2m. There are so many factors to take into account and how the extension joins the building (movement joints) roof lines and plumbing/drainage can be substantial additional costs. Adding a flat roof box is cheaper but still requires correct foundations! Pricing will depend on area but also complexity and quality.

ground screws may be able to be used in some situations rather than traditional strip footings