Roofing question

[suitcase_sally]

Which is better to use for roof decking, plywood or OSB?

[RosewoodfarmVA]

Of the 2, ply. Osb will disintegrate if one drop of water gets through the roofing. Better than either ply or osb is plain old sheathing boards. Get some rough cut 1x boards in whatever width is cheapest and use them. Your roof can leak for several years before they will get damaged. With ply or osb by the time a leak is noticed in the living space, you'll have to replace extensive amounts of ply or osb as it soaks up the water like a sponge then rots.

[Harry Chickpea]

5/8" plywood is the minimum allowed in Florida, where hurricanes happen. Ring tip nails, 3" apart, etc.. OSB is not suited for this purpose. I remember the 1x roof decking. Works fine if lapped or better yet tongue and groove, but otherwise if you step on a knot, you can break it. There can be condensation issues with it, since the joints can shrink and be colder.

[tab]

There is OSB that is exterior rated and coated with a rubberized coating. Used in NNY where there's all kinds of weather, I have seen the stuff left out in the weather for weeks. OSB has changed dramatically over the last few years. Talk to a building materials rep. SOME of them know the products.

[PyroDon]

I'll take exterior grade OSB over cheap ply wood any day .
do the same test I have lay a sheet of each out in the field leave them there for six months and then see which will still support you on a 2 ft center
I'll bet the 3 ply , ply wood wont (which BTW is currently $4 more per sheet)
Now granted 5 ply ply wood will beat OSB hands down but there your looking at nearly $28 a sheet. where as good quality OSB is around $9 a sheet.
as for the myth of OSB falling apart with a drop of water . obviously they havent dealt with it in years . Sturdy floor OSB will stand up to weather better than any ply wood sub floor no swelling or seperating after 6 months exposure

[Bentley]

Originally Posted by PyroDon

I'll take exterior grade OSB over cheap ply wood any day .
do the same test I have lay a sheet of each out in the field leave them there for six months and then see which will still support you on a 2 ft center
I'll bet the 3 ply , ply wood wont (which BTW is currently $4 more per sheet)
Now granted 5 ply ply wood will beat OSB hands down but there your looking at nearly $28 a sheet. where as good quality OSB is around $9 a sheet.
as for the myth of OSB falling apart with a drop of water . obviously they havent dealt with it in years . Sturdy floor OSB will stand up to weather better than any ply wood sub floor no swelling or seperating after 6 months exposure

What Don said is exactly right. I built a small workbench under a lean to behind my shop. I built it out of material left over from other projects. The bench top is made of two sheets of 7/16 osb. A piece I cut off of one end has been laying on the ground now for about four months. If I needed it, I could pick it up, wipe the dirt off, and use it anywhere.

[rambler]

Typically, plywood is much better. OSB has so much more pieces on the edge, if the edge of it gets wet - especially if you cut a fresh cut on it - it swells up & disintigrates.

You can find real poor plywood that is worse than premium extra special OSB.

But if you are comparing proper materials of similar ratings, I'll take the plywood any day!

--->Paul

[Yvonne's hubby]

I usually have some input on most subjects here, but roofing is simply over my head.

[glazed]

Dadgummit made me laugh ... argh.

[PyroDon]

One question where are you planning to get the sheathing from ?
I do not suggest using the OSB sold at Home depot .
warehouser OSB however is high quality and made with water proof glues as is Georgia pacific. . Ive been using both for years and never had an edge swell problem .
which ever you choose OSB or Plywood dont forget to put spacer clips between each rafter .
The main problem Ive seen with plywood is that on a poorly ventilated roof it will warp causing bulges and troughs .
if your working with 2 ft centers I do recommend using 5/8 in either case and clips .
as for the old 1x rough decking the boards cup making the roof look like a wash board which leads to leaks . when we encounter such decking we cover it with 1/4 underlayment to smooth the deck and to conform to the shingle manufacturers requirements .
Most homes in the US do not have enough ventilation . go with a full length ridge vent, and the peal and stick ice shield on the first course of felt. (it will save your eaves in the long run .

[MushCreek]

The best would be Zip System sheathing, which is plywood with a waterproof coating. The seams are taped, so the whole thing is quite water-tight. I don't know what the cost would be, though. I plan on using this when I build.

[Jolly]

OSB will hold a roofing nail better.

The house is 5/8 plywood, the shop is decked with 5/8 OSB. Gustav blew a few shingles off of the house, nothing off of the shop...

[PyroDon]

Originally Posted by MushCreek

The best would be Zip System sheathing, which is plywood with a waterproof coating. The seams are taped, so the whole thing is quite water-tight. I don't know what the cost would be, though. I plan on using this when I build.

I know quite a few builders who are trying this stuff so far there are mixed revues . the tape doesnt always hold . the biggest complaint so far is that the yape releases when rained on (the glue is not water proof )
Another question is what do you do about the nails taping them as well adds to the cost and labor.
cost is roughly $3 more a sheet here locally and the tape adds to that .
from a working stand point its very hard on saw blades and when damp with morning dew or a sprinkle its very dangerous (slick) .

[suitcase_sally]

Thanks to all for the info. Our roofer wants to use OSB, but I thought ply would be better. I see I'm not necessarily right.

RosewoodfarmVA, you may be thinking of the old particleboard from the 60's.