Another shed question - screws or nails?

Egon · Apr 7, 2015

KennyG said:
Screws are great for tension applications (like holding flooring down). However, keep in mind that they will generally only have half the shear strength of nails and, from a structural rating viewpoint, are not intended to be used in shear. For the jobs we are discussing, it probably doesn't make a difference, but an inspector would fail a structure if screws are used where nails or bolts are called for because of shear loading.

There are some screws which will meet the present building code. Can't remember the name but a Google will find them. In building construction they are used a lot with the metal hangers etc. The ones I've seen have bolt type heads with a pronounced washer area.

There are also many different types of screws specifically designed to hold boards together. They have varied screw thread patterns for different applications.

I'd use the Robertson Screws for PT lumber if building a shed that does not have to be to code.

s219 · Apr 7, 2015

Egon said:
There are some screws which will meet the present building code. Can't remember the name but a Google will find them. In building construction they are used a lot with the metal hangers etc. The ones I've seen have bolt type heads with a pronounced washer area.

I use those a lot, but they are only for metal to wood applications -- like attaching structural hardware. They will have numbers or symbols on the heads that give the load rating. Haven't seen any for wood to wood fastening though. That's generally left to deck-type screws or construction screws (normally star-drive aka torx). But as noted, they are poor in shear -- they are more brittle than nails.

dhagood · Apr 8, 2015

timberlok screws are used in specific instances for wood to wood applications, but as others have mentioned this is primarily in tension.

ultrarunner · Apr 8, 2015

KennyG said:
Screws are great for tension applications (like holding flooring down). However, keep in mind that they will generally only have half the shear strength of nails and, from a structural rating viewpoint, are not intended to be used in shear. For the jobs we are discussing, it probably doesn't make a difference, but an inspector would fail a structure if screws are used where nails or bolts are called for because of shear loading.

I've seen jobs with screws that failed to meet the seismic requirements here in California... nail, type of nail and nailing schedule are carefully checked because just about anything with plywood has a sheer component.

s219 · Apr 8, 2015

dhagood said:
timberlok screws are used in specific instances for wood to wood applications, but as others have mentioned this is primarily in tension.

I have used them, and they are very good, though I kind of view them more in the "lag" category even though they have some skinny sizes. They have very good pullout resistance from what I remember looking over the specs. The ones I used on my boat house roof were rated for something like 400# pullout when screwed in 6". Don't recall what the shear ratings are like. I was using them for uplift resistance. Saw on their website they are approved to screw into roof rafter seats through the top plate of a wall, eliminating the need for hurricane ties. Great idea if you have access to do that.

EddieWalker · Apr 8, 2015

For a building type structure, it really doesn't matter. When I say building, I'm talking something along the lines of how a house is build. Framing walls on a secure foundation, sheething, rafters or trusses and siding with headers, and secure corners. The way a house is built is that everything is resting on top of something. If you have to hang a piece of lumber off of another, it's done with approved brackets. Otherwise, it's all held there by gravity.. Imagine a world with no wind or movement of any kind and your framing will stand there without a single nail or screw. The nails and screws are just there to keep the wood from moving. Not to support anything.

The big advantage to screws over nails is with decks and exposed outdoor structures. With the extra movement and shrinkage of the wood as it dries, screws are hands down a better choice.

Eddie