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

[JohnSmith]

Further to my previous post, the standard talks about either birdsmouthed and non-birdsmouthed rafters. The later requires a wedge or framing anchor but none specifically refer to skillion roof rafters.

[r3nov8or]

In stating that, the standard is requiring full bearing on the top plate. Type of rafter doesn't matter (or it'd state the difference). Remember that AS1684 is a "minimum safe" standard.

But have a chat to your certifier in terms of "tolerance"

[JohnSmith]

Thanks for your reply.

How does the standard achieve such full bearing on the top plate with a framing anchor? The wedge I understand, but definitely never seen them either.



The only reason I ask is I have never seen skillion rafters with a birsdmouth.

[r3nov8or]

I guess a framing anchor adds bearing to the inside edge of the top plate, and the rafter itself bears on the outside edge. But would depend on what achor is used - it would have a bearing on the amount of bearing (joke, sorry )

When I demolished my c.1950s skillion garage about 12 years ago to rebuild it, the original rafters had birdsmouths And every stud was rebated into the bottom and top plates. The days when things were done "right"

[JohnSmith]

I agree with you about how things are done with less quality in mind these days.

You can thank the standard too though. Had they left the requirement to rebate the plates, it would still be done today.

If you did frame construction today, would you still rebate the plates?

[r3nov8or]

I agree with you about how things are done with less quality in mind these days.

You can thank the standard too though. Had they left the requirement to rebate the plates, it would still be done today.

If you did frame construction today, would you still rebate the plates?

Timber drying and production methods changed the game. In the 50s my old garage (indeed my house!) was built of wet forest timber from the Otways (I actually met the builder once!), and the rebates reduced the risk of the timber twisting. Not really required any longer. (Hence the inverted commas and smiley on "right")

To the birdsmouths, if you do them equidistant at each end of all your rafters, regardless that it will be a better result generally, you will also be quite sure the top of your wall frames are perfectly parallel (but 'perfectly square' and vertical will still require further measurement )