notches for rafter blocking

[chrisbrowning]

John,

AS far as the blocking between rafters tell me about the notches. I assume you start at the top with the cuts and go 1 1/2 inch. I think plans call for 2 on each block. (This is on the clipped roof). Is it better to drill holes or cut slots with a saw blade?
My question deals more with width here than anything.
thanks!

[John Raabe]

You can certainly drill holes and that is fine as well. The notched blocking that I show is much easier to do however. You precut the blocks, clamp them together and then set the saw at 45º - make 4 cuts and your done. Staple screen to the inside and your ready to put them up.

Cut the depth of the notch about the same as the ventilation space you have above the insulation. It's not critical.

[chrisbrowning]

Just want to make sure I have got this straight.
There are two layers of blocking.
1) blocking between rafters with notches  cut from the top side.
2) blocking on the outside of the sheathing centered AT each rafter with insect screen on the bottom stapled to the inside and outside of the block.
Is this correct ?

[John Raabe]

If you are using the clipped eave detail in the upper left corner of the large format 14x24 Builder's Cottage plan you don't want to do what I just described.

I just described how to do vent blocking for extended eves. Where you want a roof overhang.

If you are doing clipped eaves then use the detail with 2x8 solid blocking. This is sheathed right along with the wall and the space above it left open to the top of the rafter. Then the vent blocking and screening is done on the outside of the wall. No need to double screen or notch that blocking.

[chrisbrowning]

Ok- So in the clipped roof.
If I used 2x8 joist use 2x8 blocking
do I still notch it?

And if I used 2x4 for collar ties use 2x4 blocking.

[John Raabe]

Use blocking with a vent space above. It can be either solid blocking — full height of the rafter cut WITH notches (no need to screen) OR blocking that is shorter and leaves a 1" vent space above.

Adjust the blocking to the rafter size but keep it the same everywhere whether you have collar ties or joists.