Extension 4m square cost

FreeBear

onomatopoeia99 said:

FreeBear said:

Bleg said:

Have I stunned everyone to silence I felt like lying down in a dark room all day.

I was going to say £3-4K per square metre. So your £65K ballpark quote isn't far off. Add a bit for budget overruns and finishing, and you'd probably be looking at around £100K.

By "a bit" you seem to mean another 50%, taking it to over £6k per square metre from £3-4k?

Is the building industry really like that?  "It will cost you X" as a quote, then the final bill comes in as X+50% for the exact thing they quoted X for?

20% to allow for budget overruns. Another £25k for fitting out and furnishings depending on the level of specification. If it comes in on budget, and you are happy with a bare room, the £35k saved can be used for a world cruise or three.

Section62

onomatopoeia99 said:

FreeBear said:

Bleg said:

Have I stunned everyone to silence I felt like lying down in a dark room all day.

I was going to say £3-4K per square metre. So your £65K ballpark quote isn't far off. Add a bit for budget overruns and finishing, and you'd probably be looking at around £100K.

By "a bit" you seem to mean another 50%, taking it to over £6k per square metre from £3-4k?

Is the building industry really like that?  "It will cost you X" as a quote, then the final bill comes in as X+50% for the exact thing they quoted X for?

Bleg has a rough estimate for a half-finished extension.

Adding 50% to that to get to a budgeting figure for the finished job isn't unreasonable.

casper_gutman

onomatopoeia99 said:

FreeBear said:

Bleg said:

Have I stunned everyone to silence I felt like lying down in a dark room all day.

I was going to say £3-4K per square metre. So your £65K ballpark quote isn't far off. Add a bit for budget overruns and finishing, and you'd probably be looking at around £100K.

By "a bit" you seem to mean another 50%, taking it to over £6k per square metre from £3-4k?

Is the building industry really like that?  "It will cost you X" as a quote, then the final bill comes in as X+50% for the exact thing they quoted X for?

AFAIK you don't have a quotation for the work. Getting a firm quotation requires a lot of detail of what's required,  in terms of drawings and a written specification. Without this, you're asking builders to guess what you want and price that.

When we had an extension we paid someone to prepare planning drawings, obtained planning permission, then paid more to get detailed drawings prepared. Only then were we able to approach builders for actual quotations. It was a bit challenging to get people to quote, because it takes a lot of time to determine the likely cost of building work. We eventually managed to get three prices. The contractor we chose provided a Microsoft Excel workbook with six sheets detailing the costings, and built what they'd quoted for exactly the price they'd said.

We still spent about 50% more than this, though. Because (i) it cost thousands to get to the point where we could give builders enough detail for them to provide a firm price, (ii) unforeseen issues with the existing building came to light during the works and had to be remedied and (iii) the price didn't include finishes like the flooring, kitchen and bathroom fittings. Even after that we ran out of money for landscaping and had to live with the garden looking an absolute state until the following summer.

Now, your dining area presumably won't have kitchen and bathroom fittings, reducing that element of the cost. On the other hand, the price you have for the building shell is only an estimate and not a detailed quote. I'd say 50% over that estimated price for the shell will be a reasonable guess at the cost of the whole project. There's still a nonzero chance that won't be enough, though!

stuart45

onomatopoeia99 said:

FreeBear said:

Bleg said:

Have I stunned everyone to silence I felt like lying down in a dark room all day.

I was going to say £3-4K per square metre. So your £65K ballpark quote isn't far off. Add a bit for budget overruns and finishing, and you'd probably be looking at around £100K.

By "a bit" you seem to mean another 50%, taking it to over £6k per square metre from £3-4k?

Is the building industry really like that?  "It will cost you X" as a quote, then the final bill comes in as X+50% for the exact thing they quoted X for?

There's a difference between an estimate and a fixed quotation. An estimate is a rough idea of what a job might cost. A fixed quotation is what you will pay for the job, but for example when building an extension, you can't be certain about the foundations, so the quote will allow for that. It could also allow for material price increases nowadays, as in a year's time they could be much higher.

Albermarle

stuart45 said:

onomatopoeia99 said:

FreeBear said:

Bleg said:

Have I stunned everyone to silence I felt like lying down in a dark room all day.

I was going to say £3-4K per square metre. So your £65K ballpark quote isn't far off. Add a bit for budget overruns and finishing, and you'd probably be looking at around £100K.

By "a bit" you seem to mean another 50%, taking it to over £6k per square metre from £3-4k?

Is the building industry really like that?  "It will cost you X" as a quote, then the final bill comes in as X+50% for the exact thing they quoted X for?

There's a difference between an estimate and a fixed quotation. An estimate is a rough idea of what a job might cost. A fixed quotation is what you will pay for the job, but for example when building an extension, you can't be certain about the foundations, so the quote will allow for that. It could also allow for material price increases nowadays, as in a year's time they could be much higher.

I thought after the huge increases in 2021 that fed through into 2022, that things had steadied since then ( not gone down) and unlikely to be another big hike. I know there is Trump/Ukraine/Oil prices etc but supply chain issues after Covid were a big part of the earlier hikes, and hopefully that will not happen again !
However you never know the future of course.

flashg67

I had a 6sqm extension a couple of years ago (NW) approx 20k inc boarding and plastering but not flooring/decoration.

I struggled getting builders to turn up - luckily one of the ones who did turned out to be good and accommodating and has been back to do other work for us. 

DRP

2022 approx 5x6m flat roof extension was 60k.
included 2 flat fixed roof lights, electrics , rads, finished flooring and 4.5m patio doors.

gzoom

£2-3k per Sqm will give you a rough idea. Our build came in at £2.2k sqm from start to finish including VAT but we were at 200sqm+ so different scale.

Other way is take a rough guess now, double it and add 10%.