Rough extension cost
Discussion
Evening all, we are looking at a property and I need a rough/fag packet estimation at what and extension would cost. I’m time poor so reaching out the the PH brethren for some advice…
Single story
4m x 11m
Wall removed
Will be kitchen and living area
Based in poor staffs so no SE or Cheshire premiums!
Nothing to note in terms of access
If anyone can give me a roughy cost estimation that would be great! Thanks
Single story
4m x 11m
Wall removed
Will be kitchen and living area
Based in poor staffs so no SE or Cheshire premiums!
Nothing to note in terms of access
If anyone can give me a roughy cost estimation that would be great! Thanks
smokey mow said:
Typical build costs are £2-£3K per sqm so for a 44m2 extension it could be anywhere between £80-£130K decorated and finished.
It could easily be more through depending on how you spec things like the kitchen and bi-folds etc.
I reckon that is about right. Good builders know their value these days....but if you can get a good recommendation, maybe that could help you.It could easily be more through depending on how you spec things like the kitchen and bi-folds etc.
Matt99man said:
Evening all, we are looking at a property and I need a rough/fag packet estimation at what and extension would cost. I’m time poor so reaching out the the PH brethren for some advice…
Single story
4m x 11m
Wall removed
Will be kitchen and living area
Based in poor staffs so no SE or Cheshire premiums!
Nothing to note in terms of access
If anyone can give me a roughy cost estimation that would be great! Thanks
It's honestly going to depend on the final fit out but the foundations and lintel work will be the dearest elements of single story box at the rear. Single story
4m x 11m
Wall removed
Will be kitchen and living area
Based in poor staffs so no SE or Cheshire premiums!
Nothing to note in terms of access
If anyone can give me a roughy cost estimation that would be great! Thanks
I agree with the £2-£3k per sq meter guesstimate as a rule. As someone who doesn't like surprises I work on £3.5k for worst case initial numbers. That should also cover the kitchen fit. So £150k. You should be able to do it for much less bit I feel it helps to have a worst case scenario number in my head when negotiating to buy opposed to lowballing myself. Buy hard, in this market, unless the property is in top shape then the vendor needs to be covering a significant portion to get a good sale away.
Matt99man said:
Our renovations cost £2300/sq meter including kitchen, but the work was much more substantial in size so had some ecomices of scale. £2500/sq meter probably isn't far off a guestimate.I would worry more about the impact on light for the rest of the house. It's a big extension you are proposing, and it costs the main source of light for 3 rooms. So make sure you get plenty of glazing (expensive), but also budget for AC because glazing = solar gain, and underfloor heating because glazing = heat loss.
Getting a good builder is key, avoid anyone who can start next week. The good builders should be busy and have jobs already booked out into 2026.
gangzoom said:
Getting a good builder is key, avoid anyone who can start next week. The good builders should be busy and have jobs already booked out into 2026.
Yup, been good advice for quite a few years but the jobs appear to be drying up in quite a few parts of the country over the course of this year and some good builders are starting to have empty books. It just seems like another bit of the puzzle as to whether the economy is slowing or growing. A couple of years ago I built a 4 x 6m extension for our house. The original house was an 'L' shape so the extension filled in the 'L' , now the ground floor is a square shape.
I'm not a builder but I got most of it done myself. Unfortunately due to the ground around here (ex quarry site) we had to get the foundations piled, obviously not a DIY task so that cost about £5k
Then I put down the first couple of rows of bricks (below ground level so my lack of neatness at brick laying was no problem..), then the pre-stressed concrete beams and blocks for the suspended floor. At this point it was time to get the bricklayers in as that's a job they can do in a faction of the time it would take me to learn! That was another £6-7k I think, also £800 for steels for the two large bifold door openings.
With the walls up I fitted the flat roof and GRP'd that, put in the bi-folds. I fitted the floor insulation and then electric underfloor heating, got a local builder in at the weekend on his 'day off' to screed the floor and cut out an existing house wall + add another steel lintel for that. I think I paid him £1000 including materials.
Bifolds and roof lantern = £3k total
After electrical first fix (done by me) I lined the shell with plasterboard, I used foam adhesive which worked stupidly well in place of more traditional dot and dab. I called in plasterer, as with the bricklaying, that's not something you can learn in a hurry. Then got a qualified spark in for final fix and to complete and test the circuits.
There were a few other bits and pieces and I chose to pay for a private building inspector rather than wait for the council, also structural engineer for the steel calcs and an architect to give me a draft plan of what to build to ensure I stayed within current regs.
All in, it was about £25k - probably added £100k easily.
The only thing I hadn't expected to be so stressful/difficult was double checking that I wasn't doing anything that would break building code or in some other way cause issues down the line. Common sense is great but without professional knowledge of the building industry and how to approach certain problems, there was a lot of double guessing and research required. On one memorable occasion I stayed up late at night trying to make sense of how to maintain sufficient airflow beneath the suspended floor to meet regs - the following day the building control guy made a visit and looked at my calcs, shrugged and said "I don't know if that's right or wrong, but I can see you've left space for a few vents", which it turned out was good enough. There were other things I stressed over for a while only to later discover that, apparently, no one gives a toss
Anyway, all done now and totally worth the effort. Even if you don't want to be too 'DIY', simply managing the project yourself can save a huge amount of money - just be aware that as PM you have an heightened responsibility towards site safety.
The above is a long winded way of saying that an extension can cost a lot, or very little
I'm not a builder but I got most of it done myself. Unfortunately due to the ground around here (ex quarry site) we had to get the foundations piled, obviously not a DIY task so that cost about £5k
Then I put down the first couple of rows of bricks (below ground level so my lack of neatness at brick laying was no problem..), then the pre-stressed concrete beams and blocks for the suspended floor. At this point it was time to get the bricklayers in as that's a job they can do in a faction of the time it would take me to learn! That was another £6-7k I think, also £800 for steels for the two large bifold door openings.
With the walls up I fitted the flat roof and GRP'd that, put in the bi-folds. I fitted the floor insulation and then electric underfloor heating, got a local builder in at the weekend on his 'day off' to screed the floor and cut out an existing house wall + add another steel lintel for that. I think I paid him £1000 including materials.
Bifolds and roof lantern = £3k total
After electrical first fix (done by me) I lined the shell with plasterboard, I used foam adhesive which worked stupidly well in place of more traditional dot and dab. I called in plasterer, as with the bricklaying, that's not something you can learn in a hurry. Then got a qualified spark in for final fix and to complete and test the circuits.
There were a few other bits and pieces and I chose to pay for a private building inspector rather than wait for the council, also structural engineer for the steel calcs and an architect to give me a draft plan of what to build to ensure I stayed within current regs.
All in, it was about £25k - probably added £100k easily.
The only thing I hadn't expected to be so stressful/difficult was double checking that I wasn't doing anything that would break building code or in some other way cause issues down the line. Common sense is great but without professional knowledge of the building industry and how to approach certain problems, there was a lot of double guessing and research required. On one memorable occasion I stayed up late at night trying to make sense of how to maintain sufficient airflow beneath the suspended floor to meet regs - the following day the building control guy made a visit and looked at my calcs, shrugged and said "I don't know if that's right or wrong, but I can see you've left space for a few vents", which it turned out was good enough. There were other things I stressed over for a while only to later discover that, apparently, no one gives a toss
Anyway, all done now and totally worth the effort. Even if you don't want to be too 'DIY', simply managing the project yourself can save a huge amount of money - just be aware that as PM you have an heightened responsibility towards site safety.
The above is a long winded way of saying that an extension can cost a lot, or very little
TheDeuce said:
A couple of years ago I built a 4 x 6m extension for our house. The original house was an 'L' shape so the extension filled in the 'L' , now the ground floor is a square shape.
I'm not a builder but I got most of it done myself. Unfortunately due to the ground around here (ex quarry site) we had to get the foundations piled, obviously not a DIY task so that cost about £5k
Then I put down the first couple of rows of bricks (below ground level so my lack of neatness at brick laying was no problem..), then the pre-stressed concrete beams and blocks for the suspended floor. At this point it was time to get the bricklayers in as that's a job they can do in a faction of the time it would take me to learn! That was another £6-7k I think, also £800 for steels for the two large bifold door openings.
With the walls up I fitted the flat roof and GRP'd that, put in the bi-folds. I fitted the floor insulation and then electric underfloor heating, got a local builder in at the weekend on his 'day off' to screed the floor and cut out an existing house wall + add another steel lintel for that. I think I paid him £1000 including materials.
Bifolds and roof lantern = £3k total
After electrical first fix (done by me) I lined the shell with plasterboard, I used foam adhesive which worked stupidly well in place of more traditional dot and dab. I called in plasterer, as with the bricklaying, that's not something you can learn in a hurry. Then got a qualified spark in for final fix and to complete and test the circuits.
There were a few other bits and pieces and I chose to pay for a private building inspector rather than wait for the council, also structural engineer for the steel calcs and an architect to give me a draft plan of what to build to ensure I stayed within current regs.
All in, it was about £25k - probably added £100k easily.
The only thing I hadn't expected to be so stressful/difficult was double checking that I wasn't doing anything that would break building code or in some other way cause issues down the line. Common sense is great but without professional knowledge of the building industry and how to approach certain problems, there was a lot of double guessing and research required. On one memorable occasion I stayed up late at night trying to make sense of how to maintain sufficient airflow beneath the suspended floor to meet regs - the following day the building control guy made a visit and looked at my calcs, shrugged and said "I don't know if that's right or wrong, but I can see you've left space for a few vents", which it turned out was good enough. There were other things I stressed over for a while only to later discover that, apparently, no one gives a toss
Anyway, all done now and totally worth the effort. Even if you don't want to be too 'DIY', simply managing the project yourself can save a huge amount of money - just be aware that as PM you have an heightened responsibility towards site safety.
The above is a long winded way of saying that an extension can cost a lot, or very little
Yup. If you have the time, the foundations and pad are very easy DIY jobs and will save a good chunk. The key is being 100% sure there are absolutely no services running at the back of the property. Learning to use a mini digger is easy and BC are easy enough to comply with. I'm not a builder but I got most of it done myself. Unfortunately due to the ground around here (ex quarry site) we had to get the foundations piled, obviously not a DIY task so that cost about £5k
Then I put down the first couple of rows of bricks (below ground level so my lack of neatness at brick laying was no problem..), then the pre-stressed concrete beams and blocks for the suspended floor. At this point it was time to get the bricklayers in as that's a job they can do in a faction of the time it would take me to learn! That was another £6-7k I think, also £800 for steels for the two large bifold door openings.
With the walls up I fitted the flat roof and GRP'd that, put in the bi-folds. I fitted the floor insulation and then electric underfloor heating, got a local builder in at the weekend on his 'day off' to screed the floor and cut out an existing house wall + add another steel lintel for that. I think I paid him £1000 including materials.
Bifolds and roof lantern = £3k total
After electrical first fix (done by me) I lined the shell with plasterboard, I used foam adhesive which worked stupidly well in place of more traditional dot and dab. I called in plasterer, as with the bricklaying, that's not something you can learn in a hurry. Then got a qualified spark in for final fix and to complete and test the circuits.
There were a few other bits and pieces and I chose to pay for a private building inspector rather than wait for the council, also structural engineer for the steel calcs and an architect to give me a draft plan of what to build to ensure I stayed within current regs.
All in, it was about £25k - probably added £100k easily.
The only thing I hadn't expected to be so stressful/difficult was double checking that I wasn't doing anything that would break building code or in some other way cause issues down the line. Common sense is great but without professional knowledge of the building industry and how to approach certain problems, there was a lot of double guessing and research required. On one memorable occasion I stayed up late at night trying to make sense of how to maintain sufficient airflow beneath the suspended floor to meet regs - the following day the building control guy made a visit and looked at my calcs, shrugged and said "I don't know if that's right or wrong, but I can see you've left space for a few vents", which it turned out was good enough. There were other things I stressed over for a while only to later discover that, apparently, no one gives a toss
Anyway, all done now and totally worth the effort. Even if you don't want to be too 'DIY', simply managing the project yourself can save a huge amount of money - just be aware that as PM you have an heightened responsibility towards site safety.
The above is a long winded way of saying that an extension can cost a lot, or very little
Like you, I'd leave the above ground to professionals as well as the roofing. Tiling and plaster best done by others, same with electrics and main plumbing. But tonnes of end game jobs can also be self done such as the kitchen units, skirtings etc.
It's obviously not everyone's bag but given just how much money it saves and the days of just whacking everything on a mortgage and worrying about it later are over and we're back in a more normal world, it certainly makes sense to consider if there is any time and basic ability.
TheDeuce said:
The above is a long winded way of saying that an extension can cost a lot, or very little
It's been mentioned a few times before, Time, Cost, Quality. You pick two out of the three.DIY is fine if you can/want to it yourself, but I suspect a builder should get the job done much quicker.
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