Nails protruding through roof boards

[dynamorph]

Is there a way to apply either cedar or asphalt shingle so that the nails will not go through the other side of a 3/4" roofing board? If the nails go through then I will have to put siding on the inside of the roof. It's just a rustic porch and I don't want to have to cover the inside walls. I could put 1/2" ply on top of the roof boards, but was wondering if there is a simpler way, such as applying 2 layers of #30 felt paper. I've done cedar shingle over 1" roof boards in a shed and only a few nails came through and are not noticeable, but the roof boards I am using now are only 3/4" thick. Thanks,

-- Jeff

[dean]

Can you not use shorter nails?

[xrongor]

ill let you take it from here.

randy

[dynamorph]

Ha. Didn't think of that. I just thought you had to use the proper length nail according to the shingles.

[Robert Allison]

You do have to use the proper length of nails and according to the instructions with the shingles, they MUST protrude through plywood sheathing material or 3/4" into planking. If they don't, then you don't have a shingle warranty.

The way around this is to have two layers of decking, one for the nails to protrude through, and one for the nails to protrude INTO. The other option is your original one, and that is to cover the protruding nails with something underneath for looks.

[xrongor]

exactly.

randy

[dean]

That extra inch of nail protruding through - what exactly is it doing to hold anything down?

[Robert Allison]

I will answer, but I am not sure who you are talking to here.

If you have an inch protruding through, then your nails are too long. The nails should JUST protrude through plywood or OSB sheathing. As far as I know, it is an expansion and contraction thing. The nail that is all the way through will not expand outward because it has nothing to push against as a nail that is seated in the sheathing material does. If it is not all the way through, then as it expands, it can ONLY expand outward, which will loosen the nail and cause failures.