Rough estimate on extension

[NotAGolf]

A house has popped up in an area we're keen on moving to. It's quite run down so would need a full renovation and a hefty extension in order for it to work for us.

The existing footprint would stay as is, and we'd slap a big two-story extension across the full width at the back. The plans below show the existing footprint in black, with the proposed extension in red.

Quick summary:

• ~12.5m x 3.5m extension on ground floor
• ~9.5m x 3.5m extension on first floor
• New kitchen + utility room
• 2 x new bathrooms, plus 1 downstairs WC
• New windows and doors in extension
• Plastering and new flooring throughout the house
• Electrics, gas, and plumbing

I know this is massively lacking detail, so I'm only after a very rough ballpark to see if this a complete non-starter; so any guesses to the nearest 50k, or even 100k would be helpful. This is in the South East.

My incredibly uneducated guesses for each of the above is:

• Extension - 150k
• New kitchen + utility room - 35k
• 2 x new bathrooms, plus 1 downstairs WC - 20k
• New windows and doors in extension - 15k
• Plastering and new flooring throughout the house - 10k
• Electrics, gas, and plumbing - 15k
• Unexpected stuff - 25k
• Total: 270k

Any thoughts? Am I a million miles off?

 

[NotAGolf]

Thanks for the feedback so far all

£3000 sqm plus vat

So (12.5x3.5)+(9.5x3.5)*3000 = £231k, plus VAT = £277k. Does that estimate include kitting out the kitchens/bathrooms, or is that literally just the shell?

Why not add a fifth bedroom on top of garage and utility?

It's extra cost for space that we don't really need, and likely can't afford.

Would it not be cheaper to move into a 4 bed property? Don't see how you are going to make your house worth an extra 300k

Yes, I'd much rather pay 800k on somewhere finished over a shed worth 500k that needs 300k's worth of work, but our location is very limited (and we're not willing to budge on that), so a 700k finished place in the right area might never come up.

We're not interested in making money on the house. We'll be in the house for many many years, and negative equity isn't a concern, so if we spend 300k to make the house work for us, but it only adds 150k to the value, that's no problem.

 

[NotAGolf]

A couple of people have mentioned specs/finishing standard. I'd say mid-range would be our target. We're not going cheap, but definitely no need for top-end stuff.

I'd also be willing to do some of the work myself. Obviously things like plastering and building I'd leave to the pro's, but I'm happy to chase cables/pipework. I fitted a kitchen and a bathroom at our current place, so would be willing to do that again to trim the cost if the quotes are silly money. Same goes for decorating and some of the carpentry work.

I just want to err on the side of caution and would rather overestimate than underestimate.

My only comment would be that it might be better to redo all windows in the existing structure too to make sure they match, unless you don't mind as they're opposite sides of the house?

Yes, I'd likely want to do the front of the house as well, but they don't need to be done, so I'm excluding that cost for now.

Also, whilst i understand the upstairs layout is being done to utilise existing walls, your bedroom 2/3 seem bigger than the master. I'd be trying to steal a bit from Bedroom 3, or moving the master to the back of the house so you're not disturbed by road noise. Although that's a comment completely not knowing the views or house location!

We've got two kids, so they'd be going in the back rooms. They need the space more than we do tbh, and having them in equal sized rooms means no arguments (well, at least not about room sizes)!

 

[NotAGolf]

Just making sure this is a detached house? You'll be lucky to get planning permission for a 2 story across the full width if it's semi detached.

Yes it's detached. We've done our best to measure the 45 degree angle from the neighbours windows either side, and we should be ok to push out the ~3.5m without breaking this rule.