Such thing as a ~£20k rear extension...?

7firearcade

Recently moved in to a Victorian terrace in London and could do with extra space to enlarge the kitchen diner so thinking about extending. The most basic option would be a single storey rear extension about 4m wide and 1.5m deep. We are pretty good DIYers so would just need a shell and services. Is this anywhere near feasible for £20k? 

FreeBear

Depending on how much of the work you do yourself, it is a remote possibility. Fitting out is going to take a good chunk on top though.

Richard1212

From seeing various friends having extension works here in London, I'd say you would be cutting it close with a figure of £20,000 based on published average costs of £2500-£3500 per sq m in London and South East. 
Your proposed extension is very small but you know London prices and you probably know builders ! With the additional costs, I would guess you'd need more than £20,000 even for a shell extension. Why not get a few quotes and talk to a few builders/architects recommended to you by people you trust ? 

ThisIsWeird

If you can DIY this, then perhaps consider building it as an attached, but thermally isolated, garden room - ie on a 'conservatory' basis, retaining external quality doors between the house and the extension?
Or, would it need to be opened to the house to allow through-flow - ie make an existing room larger?
If you can avoid the complexities of Building Control, all the Archi drawings, the full-depth foundations, and all that malarkey, you can still end up with a thermally efficient room at a much reduced cost.
4" or even 6" single-skin timber frame, OSB sheathed both sides and fully insulation-filled, will match or exceed the insulation value of the majority of buildings in this country, and be cosy and easy to heat. Ext clad in whatever finish you like. 
I think.
Every chance you could do that for £10k's worth of materials.
It'll be a tough call to do this for £20k following BC, I think.

FreeBear

ThisIsWeird said: If you can avoid the complexities of Building Control, all the Archi drawings, the full-depth foundations, and all that malarkey, you can still end up with a thermally efficient room at a much reduced cost.

If you go down this route, you risk enforcement action should the local council find out (always plenty of disgruntled neighbours waiting to cause trouble). You will also have problems when you come to sell. Solicitors will ask for certificates of conformance. With no paperwork, the potential buyer may walk away or offer substantially less. If you are making permanent alterations to a property, do it right. (Building Control is more than just thermal efficiency. They also ensure proper support is built in to the structure to ensure it is safe).

ThisIsWeird

FreeBear said:

ThisIsWeird said: If you can avoid the complexities of Building Control, all the Archi drawings, the full-depth foundations, and all that malarkey, you can still end up with a thermally efficient room at a much reduced cost.

If you go down this route, you risk enforcement action should the local council find out (always plenty of disgruntled neighbours waiting to cause trouble). You will also have problems when you come to sell. Solicitors will ask for certificates of conformance. With no paperwork, the potential buyer may walk away or offer substantially less. If you are making permanent alterations to a property, do it right. (Building Control is more than just thermal efficiency. They also ensure proper support is built in to the structure to ensure it is safe).

Of course. 
But provided it is a 'separate' outbuilding, none of that applies.
It's an option, that's all. And if £20k is the limit, it may be the only realistic one they have.

GrubbyGirl_2

I don't think you stand a chance with a budget of £20k in London.  I'm in Kent had an extension done of a similar size but only single story and the cost was £40k and that was 3 years ago.  And don't forget before you even start you'll have fees to pay.  For example drawings and planning permission was £1,100, building control was £250 and because I needed a steel the structural engineer was £450.  That's almost 10% of your budget gone without a brick being laid.  Plus you will need a contingency as I would guarantee there will be something unexpected come up especially in a Victorian house.