Rafters meeting flat roof section, how to fix.

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OrangeJuice09

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Hi,
I'm constructing a roof for a single storey extension. The roof is composed of two parts, one gable (vaulted ceiling) and one flat roof. I've attached image. I'm under the understanding that usually rafters from an inclined section are connected by a birdsmouth, but internally this will create a 6inch vertical offset, which I want to avoid.
In the attached drawing, option one is not totally accurate as I havent added the birdsmouth which would reduce the offset a little.

Option 2 is ideal, internally there is no offset but not sure how to secure the rafters meeting the 2No 2x6 timber. I was thinking of using some sort of hanger/bracket.

With option 2 if fitted without offset then I cannot add gutter, so the water from the inclined section will run onto the flat roof. I assume this wont present a problem.

In terms of fixing, not sure what the inspector will pass and grateful for some advice.

Thanks
 

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What is supporting the roof where the pitched and flat meet - or is it a narrow span

I can’t 2no 6 x 2 doing the job

What is the flat roof - warm or cold?

If you run the flat roof joists the other way they can go in between the pitched rafters and it gives you more flexibility on position

I would do a warm roof: strip back tiles then take flat roof deck up the rafters, flat roof membrane too, then dress tiles back down over.
 
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The flattie will have insulation on top and the rest of the difference in height will be advantageous as an upstand.
 
The 2x6 would have a twisting force from hangers so you would need to pay attention to that force and the fixings holding them upright.
 
Notch7 said:
What is supporting the roof where the pitched and flat meet - or is it a narrow span

I can’t 2no 6 x 2 doing the job

What is the flat roof - warm or cold?

If you run the flat roof joists the other way they can go in between the pitched rafters and it gives you more flexibility on position

I would do a warm roof: strip back tiles then take flat roof deck up the rafters, flat roof membrane too, then dress tiles back down over.
Click to expand...

The span between the existing wall and the new extension is 3m to outer wall (2no 6 x 2) .
Its a cold roof (want to maintain minimum height due to neighbouring property)
2no 6 x 2 is this not adequate?
 
noseall said:
As per your top image really but with a dedicated birdsmouth as per the the opposing set of rafters.
Click to expand...
Do you mean like this new image (it still has offset though)
 

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“[GALLERY=media, 101967]Inso3 by noseall posted 3 Oct 2018 at 11:33 AM[/GALLERY]
[GALLERY=media, 101965]Inso1 by noseall posted 3 Oct 2018 at 11:33 AM[/GALLERY][GALLERY=media, 101966]Inso2 by noseall posted 3 Oct 2018 at 11:33 AM[/GALLERY]
 
OrangeJuice09 said:
The span between the existing wall and the new extension is 3m to outer wall (2no 6 x 2) .
Its a cold roof (want to maintain minimum height due to neighbouring property)
2no 6 x 2 is this not adequate?
Click to expand...

Im not sure but it sound like much support for a tiled roof one side and a flat the other.

the detailing of a cold flat roof to pitched roof junction needs to be carefully considered….you might be fine with the ventilation given the direction of joists
 
The flat roof is supported by several timbers at 450 centres running parallel to the 2No 2 x 6. So there shouldn't be much weight from the flat roof?
 
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