Illogical theory? plywood of planks

rl10851 · 01-04-2006, 04:02 PM

Am I totally off the wall with this concept? I am going to replace my roof which has 5 1/2" planks in place with 4 1/4" spaces between the planks. Code requires a solid suface on replacing the shingles. I figure I already have almost 60 % of the roof covered with planks. How illogical is it to fill in the spaces with 4 1/4" planks instead of a solid plywood overlay?
Just filling in the spaces with five 20 foot 1X4s is almost equal to 2 1/2 sheets of plywood and easier to handle. The 4 1/4" spaces are consistent. I do not see anyone else doing this so am I getting into something I will regret.

AaronB · 01-04-2006, 04:51 PM

I have seen it done, nver done it myself. Is it more cost effective? Plywood would be a smoother surface. What lumber comes in dimension 4.5""?

K2eoj · 01-04-2006, 06:42 PM

Too many cracks and the nails will pop through and break the shingle. I just went through this on a 3/12 where the original boards were tight but shrunk and left 1/8 in.+ gaps and the nails breaking the shingle was the cause of the multiple leaks. I think it was Aaron or one of the guys around here that clued me into the problem. Granted mine was a 3/12 but i vote resheath the roof and have less problems for many years to come. <P>

I also started one of those fill in projects back in the 70's. After about an hour of ripping boards we went and bought a pile of plywood and did it right in 1/10 the time. HS.

Teetorbilt · 01-04-2006, 07:00 PM

You don't give the rafter distance but if you're on 24", even a 4-1/2" board with a knot in it could be pretty weak. Here, most board sheathing is T&G and what you are refering to very old buildinds and sheds. I'd deck it over as said before.

Bonus · 01-04-2006, 10:04 PM

If you're putting arch. lam. shingles (or 3 tabs) on you've got to put ply (or OSB) down for the warranty, no? I've replaced roofs that were shingled over boards after only a few years, the shingles were all cracking at the seams between the boards.

Teetorbilt · 01-04-2006, 11:16 PM

Sorry, I forgot about the expansion/contraction aspect. Go sheathing and be done.

AaronB · 01-05-2006, 06:11 AM

It does not need to be plywood. You simply need a tightly butted roof deck. I have torn off 40 year old asphalt shingle roofs on plank that were in pretty good shape, all things considered. Shingles cracking like that most likely had another source of destruction.