Cost of completely replacing flat roof

[RoofingNewbie1]

Hi All

We've just moved into a 3-bed semi with a single-storey extension at the back with flat roof. Half of it is older and with a higher roof than the newer half. We would like to raise the level of the new part to be the same as the old roof and completely replace and re-insulate the existing covering. Part of the motivation for this is that the ceiling in the new half slopes, we assume due to sloping rafters. Does anybody have an idea as to what this is likely to cost? It will have to be a flat roof as we aren't able to have a pitched.

Thanks

 

[Mw Roofline]

You haven't told us the size. Go on £70 a square mtr plus vat to start with

 

[Smath22]

We paid £85 per metre all in for a new warm deck roof, with 126mm insulation, and mechanically fixed single ply membrane, and all metal flashing.

That's in the west country.

 

[noseall]

We would like to raise the level of the new part to be the same as the old roof and completely replace and re-insulate the existing covering.

Does this mean that you wish to remove one roof completely, alter the masonry both internally and externally then re-install new roof timbers then re-insulate and deck the lot?
£70p/m² and £85p/m² won't even come close.

This will be controlled work so either an honest reliable and experienced tradesman is necessary or a designed drawing will be required.

There are many things to consider on a job like this especially things like existing electrics (being exposed) or plumbing and their relevant cables and pipes should they run through the existing joists etc.

 

[RoofingNewbie1]

Noseall, that's pretty much the measure of it! The brickwork in the newer half will need to be raised about a foot to the level of the old half, the roof rafters removed and replaced, and a warm roof put on with all its associated insulation and roof coverings. The entire extension is about 6 metres wide and 3 metres deep.

When you say this is controlled works, do you mean we'd need planning permission? One person has said we would need this and two others said we wouldn't. Would we use an architect to do some design drawings?

Any idea of a rough cost? We're in the south east (Surrey) if that helps. Thanks!

 

[noseall]

When you say this is controlled works, do you mean we'd need planning permission?

Not P.P. no. Building regulations, yes.

Would we use an architect to do some design drawings?

Not if you can find a trustworthy and knowledgeable tradesman, no. However, if you are seeking accurate quotes, there is nothing like being armed a decent drawing. At least all the quotees will be singing from the same song-sheet.

Any idea of a rough cost? We're in the south east (Surrey) if that helps. Thanks!

None really, but start at aboot £4k and work upwards. A lot will depend upon how 'busy' the building below the proposed new roof actually is. Things to consider are logistics, protection of stuff below, time of year, scaffolding, plumbing, electrics, plaster-work in view of new wall plate straps etc, decorative finishes, blah blah blah.

The above work is in addition to the £70 - £85 per metre for the actual roof covering and insulation.