Flat roof extension / pitch roof - pp and costs

Beckyt1205

Hi.
We are planning on putting a two story extension (3m depth x 5m width) on the back of our detached house. We currently have a double fronted house with a pitched roof to the main part (approx 9x3) plus a flat roof to the rear part of the house (approx 7.5x3). The new extension will butt up to the flat roof. My query is will be allowed a flat roof on the new extension or will we have to pitch it and therefore add a pitch to the part we all ready have. And also what the rough cost difference would be to being able to just add an extra bit of flat roof as opposed to doing a full pitch. We are based in Surrey. Thanks for your help.

Furts

My local Building Regulations Department is not keen on flat roofs. I believe they issue guidance notes suggesting to applicants that flat roofs either will not be approved or only approved if no alternative is possible.

Builders such as Barratt, Persimmon. Bellway etc never put flat roofs on conventional houses. In addition the NHBC dislike them.

Flat roofs are bad news and best avoided where ever possible.

System

Furts wrote: »

My local Building Regulations Department is not keen on flat roofs. I believe they issue guidance notes suggesting to applicants that flat roofs either will not be approved or only approved if no alternative is possible.

Builders such as Barratt, Persimmon. Bellway etc never put flat roofs on conventional houses. In addition the NHBC dislike them.

Flat roofs are bad news and best avoided where ever possible.

I don't know where to even start with that one, so much mis-information there

Furts

the_r_sole wrote: »

I don't know where to even start with that one, so much mis-information there

I will agree to dis-agree on this one. The gist is there were so many flat roof new build failures after the seventies and eighties building style, then issues with warm roofs and cold roofs, plus ventilation issues on extensions continuing after this. this is the technical side.

Then from aesthetics, no houses within a mile of my home would be allowed a flat roof on the front or side extension.

Pitched roofs have a life span far exceeding that of flat roofs - this is recognised by NHBC and by Building Control. They can cost more - which is why builders went for the flat roofs in the first place.

My local authority tries to encourage applicants not to specify them. But it also accepts there are situations where they are required, plus everyone is looking for the cheapest build option.

System

ok, I'll break it down a bit

Furts wrote: »

My local Building Regulations Department is not keen on flat roofs. I believe they issue guidance notes suggesting to applicants that flat roofs either will not be approved or only approved if no alternative is possible.
.

this is completely outside the remit of building regulations departments - they are there to ensure that regulations are adhered to, they can't and won't say that things will only be approved if there is no alternative, they can only refuse permission for something that does not meet the regulations.

Furts wrote: »

Builders such as Barratt, Persimmon. Bellway etc never put flat roofs on conventional houses.
.

they never put flat roofs on standard houses as pitched roofs offer a cheaper instal and give extra room in the roofspace - however they will put flat roofs onto contemporary housetypes or where required by planning departments.

Furts wrote: »

In addition the NHBC dislike them.

but they do have nhbc approved details for flat roof contruction?

Furts wrote: »

The gist is there were so many flat roof new build failures after the seventies and eighties building style.

so you think there has been no advance in flat roofs since the 70's and 80's?! it much like telling someone not to use windows as they leak heat since they are single glazed!

Furts wrote: »

, then issues with warm roofs and cold roofs, plus ventilation issues on extensions continuing after this. this is the technical side.

all these issues could occur with any roof, it's all about it being detailed and constructed properly

Furts wrote: »

Then from aesthetics, no houses within a mile of my home would be allowed a flat roof on the front or side extension.
.

really? i'd like to see proof of that

Furts wrote: »

Pitched roofs have a life span far exceeding that of flat roofs - this is recognised by NHBC and by Building Control.

i'd like to see evidence of that, again it's down to the detail you can't say all flat roof contructions are x and all pitched roofs are y

Furts wrote: »

My local authority tries to encourage applicants not to specify them.

really? they overstep their remit like that? do they have published information to that effect?

Kiran

I was going to reply but I think the_r_sole's response covers the main points. lol

ritesh

Flat roofing materials have come a long long way. A little research shows materials such as EPDM for roof covering. Also the use of celotex for insulation in warm roofs. In fact flat roofs are quite popular!

I am in the processs of converting three garages into a garden office and looking to use a flat roof construction.

Furts

My post may not be popular with some mse users. But all posts are archived. In the future someone may be looking for professional advice on the subject of flat roofs. With this is mind, I stand by each comment I made.

Beckyt1205

Thanks for your responses. Does anyone have an idea on rough cost comparisons. 1) installing a 3m x 5m flat roof on an extension and butting it up to an existing flat roof. Versus 2) installing a 3x5m pitch roof on an extension and also adding a pitch roof to 3x7m to a current flat roof.
I realise this is difficult to estimate but even a rough idea of costs would help us decide whether to try and save money short term and pursue the flat roof option. Thanks