Building costs for annexe

[Pleasedontdothat]

We’ve got planning permission to turn some derelict outbuildings into a one-bedroom annexe and open-fronted garage which would be used for family and friends coming to visit - I’d airbnb it the rest of the time. The annexe would be a bedroom with en-suite shower and loo and a kitchen/living room with a fabulous view over our orchard and stream. I’ve just had the first quote back and it’s more than £200k without factoring in furniture and fitting out the kitchen. It seems staggeringly high to me ! For context we paid £600k for the four bedroom farmhouse and 16 acres of land. Is that really what building work costs at the moment? I’m not sure I can justify that kind of money.. but I need to do something with the buildings because they are literally collapsing.

How derelict and how many square metres? Does the building already have services like water and electricity or do they have to run those to it?

BIL was given a rough figure of £80k to convert a garage into accommodation with a living room, bedroom, bathroom, and kitchen. Garage isn't attached to the house but it's very close. Coversion would have been basic around the kitchen and bathroom, no fancy stuff there.

The building at the end which is going to be the garage is collapsing - currently held together with vegetation - but the other two buildings aren’t in such a bad way. They need to be insulated, proper roof, windows, doors etc There’s electricity already - we rewired the stables and outbuildings 18 months ago so that’s all up to date and there’s water close by so relatively easy to run to the annexe. We do need to update the septic tank system but that would need to be done anyway. It just seems disproportionately expensive compared to building projects I’ve done before 🤷‍♀️

Sorry - missed out the size - I’d say the average size of each of the buildings (all connected) is 4x4 m so not huge but not tiny

So it's priced at about £4,000 a square metre if it's 50 m2. Fairly high but that doesn't include the car port and the builder's hate-working-on-old-buildings 'tax'.

I was expecting it to be over £100k - if it had been around £120k I’d have been happy but could have understood a quote up to £150k but this seems disproportionately high. We’re not in an expensive area of the UK either. I’m keeping my fingers crossed for the other quotes.

I’ve got a thread in here from a year or so ago. We extended our main house and created an attached annexe to the side.

For various reasons we ended up opting for a modular build. Much cheaper, quicker, fixed price, and it’s more environmentally friendly. The insulation in the modular build is excellent- it’s reduced the need for heating significantly.

We’ve put in kitchens, toilets, and bathrooms plus skylights. Every time a new trade comes in they always compliment us and ask about the extension/annexe!

I’d opt for the same route again in a flash. To a plastered finish it was way under £2k per square metre. I’d have to work it out exactly but very significantly less!

would you mind telling me what modular build company you used?