Skillion roof for Garage

[JohnSmith]

Hi all,

Happy New Year.

I have a question about a Skillion roof for a garage.

The rafters rest on the top plate. If the angle of slope is 10°, is it a requirement to 'birdsmouth' the rafter onto the top plate, even though it is minor?

Regards,
John

[Stuckster]

Hi John,

No, not a requirement.

Standard AS1684 2021

7.3.13.3 Birdsmouthed and non-birdsmouthed rafters
Where rafters are not birdsmouthed over top plates... Rafters shallbe supported by means of wedges or other alternative support systems, such as framinganchors that provide equivalent bearing support.

Nominal fixings for rafters to top plates of Non-coupled roofs are 2 x 75mm skew nails. That's the bare minimum. Multigrips or triplegrips (framing anchors) with connector nails will be much stronger. Structural screws down through the top edge of the rafter into the top plate should also be acceptable. A birdsmouth will create a more stable connection, but not mandatory.