minimum roof pitch under permitted development

[djdna2000]

Hi all

I am building an extension to the rear of my house under permitted development, so 3m deep. To maximise the height of the bifold doors I want to minimise the pitch of the roof (it is going to be mainly glazed anyhow, prob 80% assuming my SAP calculation comes back OK). The architectural draughtsman who drew the plans isn't being particularly helpful but suggested min pitch was 13 degrees.

I couldn't find any reference to this in the regs so can it be less? I don't care what covering goes on the non-glazed bit, just flat roof stuff if necessary.

 

[freddiemercurystwin]

The pitch of a pitched roof is determined by the type of roof tiles specified as some will go a lot lower than others. Down at 13° you are very limited in what you can use so especially if you want to match your main roof (which really you should be doing in order to meet PD criteria anyway). Also bear in mind that often Building Control will not sign off a roof with tiles lower than their manufacturers specified minimum. Really a roof of 13° is pretty flat in infact a roof of 10° or less is technically classed as a flat roof, that's how low it is! You could consider doing it as a flat roof as well as you're practically doing that anyway as all the common flat roof materials will handle that pitch OK. You could consider zinc as that's (IMO) a very attractive flat roof material and not (too) pricey.

In order to comply with the PD criteria this is a good guide: http://www.planningportal.gov.uk/permission/commonprojects/extensions/

 

[djdna2000]

Thanks for that. OK so you are basically saying that if I use a flat roof material (yes zinc would be nice actually) then I can have whatever pitch I want? I will go back to the guy doing the plans and see what he thinks.

 

[leew2]

If building a single story extension under PD then there is no minimum pitch, roof can be flat if you want a flat roof.

 

[^woody^]

Height of the eaves and ridge are the criteria for PD, not pitch

 

[jeds]

Be careful though. PD rules state that materials must be similar to those used in the main house. So if you have standard tiled roofs a flat zinc roof wouldn't be acceptable.

 

[paulandfrodo]

jeds is correct. You have to use the same materials as in the rest of the property. Your going to be pushing it to get less than 18 degs. Also depends upon where you live as to what laps you need to have on your tiles - due to prevailing weather conditions. Always start at the max point allowed in pd - 4m to the ridge and work backwards knowing what the distance/fall is going to be. Then this will give you the MAX height you can have, less joists, plasterboard ect. It's simple maths. ok, I get my girlfriend to do the maths !

I managed last year to do a 4.2 extension as I found some old records with a toilet on the back of the house. got a written agreement it was present then went ahead and built... All signed off....

 

[freddiemercurystwin]

Pretty sure I recall reading an appeal whereby when an existing dwelling did not have an existing flat roof there was nothing to match therefore the appellant was able to use their flat roof material of choice.

You cannot match something that does not exist.

 

[paulandfrodo]

freddy,

I had to read that post and think about it... Right, i see what your getting at. I think he's going to be safer with a pitched roof with, err, traditional materials. God, if I tried that on in Winchester my local BCO would just raise his eyebrow and walk away... Well, after coughing and muttering a swear word at the same time !