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Original poster

Cost of building an extention

17 replies

ThirtySevenA · 12/05/2015 22:15

We're planning a building project which involves knocking down the converted garage on the side of our end of terrace, and then building a two storey extension on that space with a dormered attic room above. It will basically be three medium sized rectangular rooms on top of each other, with a bathroom fitted in on the first floor and a stairwell at the back. Around 50 sq metres in total.

The estimate we've been quoted for this job so far amounts to around £300k including VAT, architects' fees, fixtures and fittings (there will be a kitchen and bathroom). Can anyone comment on whether this is shockingly extortionate (as it seems to me) or reasonable?

NB We are in an expensive area in Cambridge and the estimate was provided by a fairly high-end architect who used a quantity surveyor. Has anyone got any ideas on what professionals we could use to get this project done within our budget of more like £170k - £200k all in?

OP posts:
Original poster
ThirtySevenA · 13/05/2015 10:06

Bump

OP posts:
reallybadidea · 13/05/2015 10:12

Hi, I live in Cambridgeshire and had an extension a few years ago. We used a local builder who was a fraction of the price of other quotes we had and we were extremely happy with him. If you PM me I'm happy to give you his details.

Wittynewnameifonly · 13/05/2015 10:20

I have sent you a private message.

MrsFlorrick · 14/05/2015 21:13

That's £6000 per square m build cost. Even with a high end finish it ought to be more like £2000 p square m.

Unless you have a complex build (lots of steel work or complex foundations such a piles) which would cost more?

Original poster
ThirtySevenA · 14/05/2015 22:02

Thanks MrsFlorrick, I agree. It's not a complex job at all, although I think the architect would have preferred it to be. We're going back the drawing board. I've been given some great suggestions and recommendations from people on this thread.

OP posts:
mandy214 · 14/05/2015 22:14

Do you know you'll get planning permission for that?

Original poster
ThirtySevenA · 14/05/2015 22:43

Hi mandy214. We're reasonably confident about planning permission although it is a conservation area. The architect we were using had informal conversations with the planning officer and the conservation officer and showed them some plans, and they both made positive noises. Also we had a similar plan some years ago which got quite far down the planning route before we pulled it for other reasons.

OP posts:
TeddyBee · 15/05/2015 11:54

That's madness. I added around 75sqm over three stories for £150k including three bathrooms, a kitchen and a utility room. In London. I wouldn't recommend my builder tbh, but it all got done in the end.

MrsFlorrick · 15/05/2015 13:22

So is this the architects and QS costings?? Shock

Bear in mind architects earn a % of the total build cost so like it to be massive so they can earn more.

If so I would ask the architect what exactly you're getting which is so special that it is 3xtimes above the cost of what is considered higher end finish.

Bear in mind that at £2000 psqm building cost, your new kitchen would be an extra. However it should include everything apart from kitchen cabinetry, worktops and appliances.

Could you look for perhaps a structural engineer and a building surveyor to carry it out rather than an architect.

Unless your design is complex, I don't see why you need an architect for an extension. Engineer and surveyor will do a good job without the massive cost add on.

I would look elsewhere if I were you.

sugarhoops · 15/05/2015 14:26

Have you only had one quote so far? If so, could just be that the builder you've asked to quote simply doesn't want the job....but doesn't want to lose face by not quoting so has done silly huge quote that he knows you won't accept.

Get some more quotes and ask for builders opinions on the plans.... Could be that architect has made it mega complex.

We're in middle of a 2 storey extension, 30sq meters and is coming in at £72k incl. vat. A friend round the corner had plans drawn up for a 3 storey extension, similar sq m to you, quote came in at £120k, but only from one builder. They're downscaling to 2 stories now. We're in the south of England. Good luck, you'll get there, it's just a bit of faffing to get things off the ground (in my experience!). Our plans were approved last November, now 3 wks into build and all good so far....touch wood!

zoemaguire · 17/05/2015 04:36

We had a two storey extension built, very similar area/house, a few years ago, including new kitchen and bathroom, and all in cost was a third of what you have been quoted, for a pretty high quality finish! Again, I wouldn't recommend our builder, but 300k sounds extortionate!

vienaa · 17/05/2015 07:42

We just got our bill for the structural engineer and it was more than I expected, he charged us £595 with vat... Just for a 2 storey extension I was quite shocked with the amount of beam work that needs doing and its only a bedroom sitting on the top, we need 2 beams rear and front bolted together, and a windpost, we have to knock a bit out in the old wall and build a brick padstone...

zeeww · 17/05/2015 08:16

Did the Structural Engineer not give you a quote before proceeding? Ours was a 2 storey extension too with 3 beams (back wall down, new bedroom upstairs) - quote for structural calcs was 350+VAT. He quoted based on the drawings so he knew exactly what was required before we agreed for him to proceed.

vienaa · 17/05/2015 09:20

My architect sent the plans to a SE and i got a email saying they charge £50 an hour and I said fine to the architect, but then we changed the layout of the inside so everything went on hold. When everything was all clear my architect sent them to the SE, I thought I had to do it myself. I also have another massive beam which when we knock the wall between the dining room and kitchen.... I have to admit my plans from the SE is very detailed also there is lots of other bits he put on there.. I can see where the money went.... All I am saying I can't believe so much metal for just a upstairs bedroom

zeeww · 17/05/2015 15:46

Charged per hour..... THats probably why, but that doesn't mean your SE had taken the Mickey. Ours were fixed price based on the agreed plans.

We were advised to approach the SE only after we are happy with our plans (of course, that should stop you changing your mind on the internal layout, but recalcs may be required)

parkes30 · 17/05/2015 16:46

Hi. I own a 1930's semi. Small kitchen then lounge/diner knocked through with patio doors into conservatory. I want to put a wall back in to create a small lounge then knock the wall down into the kitchen & extend out getting rid of the awful conservatory. Any ideas about cost not including the actual kitchen. I know it's about £1-2000 per sqm for the extension build but what about all the costs of knocking through,adding a stud wall, electrics, etc. I have no clue and as a single woman on my own no one to ask. Appreciate any advice. Smile

sugarhoops · 18/05/2015 14:11

parkes if you bank on it being £2k per sq/m (which includes the steels / knocking through etc, but not the actual kitchen), then you shouldn't go far wrong. Plus £3k fees for planning / structural engineers etc.
UNless you're south east, in which case it might be nearer £2.5k per sq/m.

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