Extension roof advise

[Sonnypaul]

Evening everyone.

Have a small extension coming up and need a little advise on the roof.

Most of the extensions go out about 3 meters and I tend to measure down about 150mm from the sill to the top of the wall plate.

This extension however is only going out about 2200mm.

I'm going to be using Redlands 49, smooth, min pitch 17.5 degrees as most of you proberly know.

I don't want to go right under the sill if I can avoid it so any help would be great.

Cheers

Read more: //www.diynot.com/diy/threads/pitching-small-extension-roof.416655/#ixzz3HZWr63mr

 

[noseall]

Evening everyone.

Have a small extension coming up and need a little advise on the roof.

Following so far.....

Most of the extensions go out about 3 meters and I tend to measure down about 150mm from the sill to the top of the wall plate.

I think I get it but a wee bit vague.....

This extension however is only going out about 2200mm.

I'm going to be using Redlands 49, smooth, min pitch 17.5 degrees as most of you proberly know.

Do we....?

I don't want to go right under the sill if I can avoid it so any help would be great.

Ah, gotcha!
You intend building an extension that will project 2.2m out from the existing house and wish to have a small upstand of lead beneath the upstairs window sills, yes?

Only way to guarantee this, is to work from the upstairs window sill down and see if your pitch is feasible without compromising head height (usually 2.1m) on the proposed extension window and doors etc. A bit of measuring and a bit of trig' and it is simple for an experienced designer to work out.

Only thing to look out for is large openings with tall lintels that may compromise proposed wall plate height position and unfeasibly low (existing) upstairs window sills.

 

[noseall]

One way you could do it is to mock up a dummy rafter (correct depth) complete with a b/m at the internal wall plate position. This rafter could be cut with a 17.5 degree angle at each end and be the correct length complete with soffit overhang.

You could then pitch up the rafter against the house wall finishing at say 200mm down from the upstairs sills.

You would then fit an upright length of 100mm x 50mm into the crook of the b/m which would act as your prop and represent the internal wall and wall plate etc. You would determine the length of the prop by using an upright level on your rafter plumb cut.

All you would need do then is mark off onto the upright timber the dpc height, the window head, lintel depth and wall plate and see if it works. Hey presto!

Only thing I would do is say fit a long length of timber up along side the rafter rather than try and fit one into the crook of the b/m because it gives you better freedom of movement with the rafter.

 

[Sonnypaul]

One way you could do it is to mock up a dummy rafter (correct depth) complete with a b/m at the internal wall plate position. This rafter could be cut with a 17.5 degree angle at each end and be the correct length complete with soffit overhang.

You could then pitch up the rafter against the house wall finishing at say 200mm down from the upstairs sills.

You would then fit an upright length of 100mm x 50mm into the crook of the b/m which would act as your prop and represent the internal wall and wall plate etc. You would determine the length of the prop by using an upright level on your rafter plumb cut.

All you would need do then is mark off onto the upright timber the dpc height, the window head, lintel depth and wall plate and see if it works. Hey presto!

Only thing I would do is say fit a long length of timber up along side the rafter rather than try and fit one into the crook of the b/m because it gives you better freedom of movement with the rafter.

Hi noseall thanks for replying.

Yes I understand what you mean and glad you understood what I meant ha.
Find it hard to explain sometimes when typing.

I'm going to wait till the brickie is up to wall plate height and like you said cut a rafter at 17.5 and offer it up.

What I'm trying to get around is having lead flashing right under the sill and because this extension is not going out 3 meters I thought there may be a way round it.

So noseall do ya think I should just cut a 17.5 and play it safe, regardless of the height from top of wall plate to sill, weather there's 100mm or 350mm left above.

Hope you understand matey my typing skills are ****e