Cost for possible extension before putting an offer in on the house. ?

[catpark]

Just had an offer on my house which we've accepted. We live in a small town and want a 3 bed semi with a decent sized Kitchen and living room. There has only been one house like this that has come on the market in our price range since October and it sold within weeks. We don't want to move again so we need the house to be right.

There is however a few 2 bed semi's on the market with a big side drive. Now i'm thinking about buying one and putting a double storey extension on the side. It would give us a large living room (Would take the gable wall out and have the extension as part of it ). and a utility room/toilet downstairs and the 3rd bedroom and another bathroom/storage upstairs.

But we have no clue about how much this would cost us. We don't want to make an offer then find out the cost is too high, and we can't exactly ask a builder for a quote because it's not our house.

Extension would be roughly 28m2 on each level. Anyone have a rough idea about the costing for it ? Should we be using £1000 per m2 so costing about £28,000 per floor or is the second floor lower than the 1000 per m2 ??

Thanks.

You can get an average cost with this calculator

That one says about £45,000 but another I tried came out at £54,000. Both of those figures are doable. But do these calculators actually give a realistic figure compared to actual builders ?

we had a two storey extension put on the side of our house, completed 3 years ago.

Consists of two rooms downstairs (not big plus cloakroom). Staircase and upstairs bedroom and tiny shower room.

Cost about £60/70k all told. We had to have bespoke windows, and my DH insisted on oak staircase and beams. Plus underfloor heating. So with basic construction I guess would have been about 10K less. This included flooring and bathroom fixtures.

It depends where you are in the country. Have just asked my builder exactly the same question today. We are near Bath, and my builder is not the cheapest around because he's v good! He reckoned £1500/sq m/floor, plus fittings (bathrooms/kitchens etc) plus VAT. He said he used to quote around £1000 ten years ago.

Have not tested this out yet, but he's right about most things.

I'm in Scotland. igetcrazytoo how many m2 was your extension ?

I've been on the council's planning website and there are similar extensions to the type we want on it. It also has the building warrants online which have a cost of work price on them. Anyone know if this is the actual amount that the extension cost or is it a rough guide on them ? The most recent building warrant was issued in January and was £50,000.

£1000 per m2 is a good realistic guide - our 2 storey extension is a similar size and will be coming in less than that but I suspect that's only because it is part of a bigger job - we're also restructuring our existing layout as well as renovating every single room. You will be doing well if quotes come in under £56K and then, you can still haggle.

Our downstairs extension will be a reception area open plan to existing half of the house. The upstairs extension will be master bedroom and ensuite bathroom linking to an existing dressing room. No new staircase required and no underfloor heating. With midrange fixtures and fittings carefully sourced to cut down on costs, it will come in under £60K. BUT...it's part of a bigger renovation so I'm getting a better price overall. Aim for a fixed price and try to eliminate provisional sums as much as possible - this means that you need to have a firm idea as to the fixtures and fittings you want/can afford early on. A good/experienced builder will be able to give you a headsup if any of your sums are plain unrealistic but tbh, your architect should design with your budget in mind.

That's interesting Myron if the price includes fixtures and fittings. I thought the prices would just be the building, no bathrooms etc.

We would have around £60,000 in our budget for the build and to have the bathrooms fitted and tiled. So it looks like it could be done in our bedget and we'd get a decet sized 3rd bedroom. The 3rd bedroom in teh normal 3 bed houses is just a single really.

Thanks all for your help, will have to go over figures with DH and decide if we should go for it !

I'd say add on at least 15k to whatever the predictors say as once you start the work extra cots always come out of the woodwork...

I don't see why you can't get a builder to come to the house with you and give you a rough estimate? Provided the current owner doesn't mind (and why would they, if its going to encourage you to buy the house). Bear in mind it'll only be an estimate of course, and there's the risk you'll give the current owner the idea to extend!