3/4" pine boards instead of plywood or osb sheathing

[Jmeng1026]

I was contacted by an individual who is constructing a barn with a gambrel style roof. He is using pre-engineering gambrel roof trusses. He asked if he could use 3/4" pine boards (8" wide) for the roof sheathing. He would install them tight together(not spaced apart like strapping). The boards would not be tongue and groove, just butted up to each other.

Any issues with this?

Should he use h-clips?

Attached is a picture of the roof truss. There will be floor joists fastened to the side of the trusses where they sit on the wall.

 

[driftLimiter]

If you need the sheathing for a diaphragm you would need to check with NDS to see if that qualifies as a diaphragm and if it has enough strength.

Should he use h-clips? Is there enough Dead load to counter the wind uplift at the truss connection? Or perhaps is there some other mechanism to resist the wind uplift?

Kind feels like your passing the buck here... What calcs have you done? What calcs should be done for something like this?

 

[BridgeSmith]

If the roof sheathing needs to act as a diaphragm, you could specify installation of some of the 1x8s as diagonal braces along the underside of the sheathing boards.

 

[phamENG]

NDS SDPWS has diaphragm tables for lumber diaphragms. This is exactly how wood floors and roofs were built before plywood was invented/available/trusted.

By H clips do you mean the little clips that go between plywood sheets? I'd say no, but it also depends on the roofing material. If it's metal roofing, no. Some sort of fragile shingle that will break with minor variations in the roof plane? Maybe pick a different roof for your barn.

 

[SWComposites]

Yeah, thousands of barns were likely built with lumber roof sheathing.

And my 1914 Seattle house had skip sheathed 1x6 boards covered with cedar shakes.

 

[gte447f]

"Any issues with this?" No, of course not, but it depends. A few thoughts:

There are probably 10's of millions of barns (and old homes) built with wood plank floor and roof decks (i.e. diaphragms).

In general, wood plank diaphragms have less in-plane shear strength and stiffness than modern plywood or OSB panel diaphragms. As phamENG said, NDS SDPWS has diaphragm tables for lumber diaphragms if you need to design or check them.

H-clips are for vertical load sharing between the edges of crappy (i.e. relatively thin) plywood and OSB panels.
Personally I think they are kind of a waste of time, certainly for design for strength. They probably help with long term serviceability deflection so that panel edges don't telegraph through shingled roofs as bad when using thin panels. I wouldn't think of specifying them for a lumber deck.

In many locations, barns and agricultural buildings are exempt from building code requirements. Your mileage (and location) may vary.

 

[DoubleStud]

you can do perpendicular but the value is very low. Diagonal will be a lot better and will outperform plywood.

 

[XR250]

If screw-down metal roofing is installed, that would likely provide the diaphragm required unless you're in a high wind or seismic area.