Questions for 2x8 T&G roof decking nailing

[Lennyzx11]

Hi all.
I'll get right to it.
I have a Bostitch 21° framing nailer that I'd like to use putting my roof decking on but want to make sure it's the right choice vs screws.
The pitch(es) are 7:12 & 8:12.
The boards are 2x8" by 16'.
Thank you for advice.
Lenny

1. 16 penny nails are called for 2" t&g I researched. That's a 3 1/2" length. What would be the corresponding recommended size (wire)? Galvanized, framing, finish, etc?

2. The ends are NOT face t&g. Do I need to land on a rafter with each connection and not out in "free air"?
(The rafters are 24-28" apart).

3. Is it 2 nails per supporting member for 2x8 face nailed? This will be covered with underlayment and shingles.

[doc henderson]

good morning.  will the deck be seen from the underside?  My framing nails are also referred to by the penny gauge.  I have used ring shank, but I do not recall them coming as large as that.  i think the ends should join over a rafter.  you could use a spline if it will be seen, and you need max. coverage.  you would hate to have an end stick up or down especially if seen.  My two cents, no charge!  

[beenthere]

Lenny
What species? What is the underlayment intended to be?

Are you following manufacturer's recommendations with this fastening plan? 

[Lennyzx11]

good morning.  will the deck be seen from the underside?  My framing nails are also referred to by the penny gauge.  I have used ring shank, but I do not recall them coming as large as that.  i think the ends should join over a rafter.  you could use a spline if it will be seen, and you need max. coverage.  you would hate to have an end stick up or down especially if seen.  My two cents, no charge!  

I agree Doc. I didn't know if the T&G. Was consider sufficient support. I'll be safe and cut to the rafter support.
Thanks

[Lennyzx11]

Lenny
What species? What is the underlayment intended to be?

Are you following manufacturer's recommendations with this fastening plan?

It appears to be EWP or hemlock. I'll have to ask the local mill that made it.
There are no manufacturer's plans.
The Timberframehq plans stop at the frame and only the notation "2x t&g decking" is on the plans.
Hence I thought I'd ask you guys best practice guidelines.

The underlayment is intended to be old school 30lb felt but I'm open to suggestions otherwise if warranted.
Lenny

[rjwoelk]

I would go with self adhesive  ice and water shield membrane.  Why are the rafters 28 inches?

[beenthere]

I understood underlayment as OSB or plywood. 
With felt, I think you will telegraph the individual deck boards through to your shingles unless wood shingles. The decking is going to move, I believe, with mc changes and drying in place. 

[doc henderson]

any insulation anywhere?

[Don P]

This is from the nailing schedule in chapter 6 of the IRC, check out item #25



 

My gun shoots 0.131's so by that table I'd put in 4 per bearing. Most people have never driven a 16 common, I think a sinker is .149.

This is from the AITC Timber Construction Manual. It explains controlled random layout patterns.


 

[Lennyzx11]

any insulation anywhere?

No. It's an open carport/pavilion.

[Lennyzx11]

I understood underlayment as OSB or plywood.
With felt, I think you will telegraph the individual deck boards through to your shingles unless wood shingles. The decking is going to move, I believe, with mc changes and drying in place.

Hmmm... I never thought of that. I assumed the 2x8s as structurally sound but never thought about the flexible layers on top forming to the board lines. 
Something to think about.
Thanks for the heads up!

[Lennyzx11]

I would go with self adhesive  ice and water shield membrane.  Why are the rafters 28 inches?

The plans called for 30" on center. With the way it worked out due to a small extension to accommodate some length added to tie to the old shop, the distances ended up being 24" between to be uniform. So 28" on center.
I have been leaning to using the membrane. I used it on my wraparound porch that I built on the house and liked how it turned out.

[Lennyzx11]

This is from the nailing schedule in chapter 6 of the IRC, check out item #25



 

My gun shoots 0.131's so by that table I'd put in 4 per bearing. Most people have never driven a 16 common, I think a sinker is .149.

This is from the AITC Timber Construction Manual. It explains controlled random layout patterns.

Thanks Don. Mine shoots .131 also. So that recommendation of 4 per support sounds like a plan. 

[scsmith42]

Most framing nailers won't shoot 3.5" nails, so be sure to check your maximum length.

I had to buy my 3.5" ring / spiral shank nail gun nails from Maze.  Expensive but top quality.

Locally I can only buy 3"

[Ljohnsaw]

My Porter Cable will shoot 3.5" nails.  I bought some to toenail the blocking in my floor joists.  It's a 21° gun so it uses the plastic connectors on the strips.  The nails shoot fine but the thicker wire with the plastic doesn't slide well in the magazine.  So, after each shot you have to bang it or physically push the strip forward.  Kind of a pain.  BUT, much better than hand nailing!