I am wondering if screws are considered to be structural fasteners such as in use with rafters, and joists or whether nails are the only structural fasteners. Cheers
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Structural lags are used all the time. Why are you wondering?
I was wondering because sometimes it is easier to screw in joist hangers and screw in rafter tails without splitting them. We generally use the pressure treated screws but by the sounds of things they are too brittle. Cheers for the reply.
Simpson has some special screws they sell for hangers, and GRK screws are good for pretty much anywhere you'd use a nail (and then some). And large (lag) screws are considered reliable in shear, simply due to their bulk. Machine bolts (the type that takes a nut) are available with ratings, and those ratings can generally be trusted.However, as stated a standard drywall or deck screw (or conventional cut thread wood screw) is too unreliable -- some may be great, but others are carp, and you can't tell the difference because there are no standards or ratings.
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Those Simpson ones are 1/4" diameter and are ment for specific hangers. The other ones they have are ment for putting together workbenches and aren't very good at all.Rebuilding my home in Cypress, CA
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I used screws, with the approval of my Building Inspector, on my garage roof reframe. I had the same question as you a few year back that I asked on the board - do a search on my screenname and screws to retrace some of those threads.
Here are some things I can say of my experience:
Use at least #9 or #10 screws, not #8. The larger screws fit the .162 size holes of most of the hangers anyway.
I had great success with #9 DeckMate Square Drive 3.5" screws (only available at HD) for things like toe fastening. For face fastening plates onto 2x, I use McFeely's #10 1.5" round washer head. Unfortunatly neither has a self drilling tip. McFeely's makes a ProMax line that is great for this, I've been working with their 3" #10's alot lately. Unfortunatly the phased out the round washer head of that style. I've not yet compared flat head with washer head on a shear connector.
Neither of those screws is brittle. I can take the Deckmate and bend it into a corkscrew. GripRite brand, on the other hand, is brittle - I snapped a ton of those.
Screws are not cheaper nor faster than nails. The business of homebuilding requires cheap and fast, so you won't find much actual technical information about screws in the uses you are asking about. Not enough demand for that kind of info.Rebuilding my home in Cypress, CA
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Simpson makes screws that are designed for their hangers, in several different sizes.
I have used pocket hole screws for framing fix-ups on my place. But mostly because I messed up my arm, and if I swing a hammer more than a few times my elbow feels like I've been driving the nails through it.
Someone in the past did things like cut studs to build a box in to the adjacent closet to hold a TV, didn't do anything close to "right". Just cut the studs, and laid a 1X4 across them and built a box out of edge nailed 3/4 plywood sticking back into the closet, and then ran an extension cord down into the back of the box and screwed it onto the terminal on the plug in.
That was a fun one to fix.
As I stated earlier, I've only seen the #8 wafer head screw by Simpson for their workbench kits. There are much better fasteners than those. I've only seen them in one size too - I'd love to see a link to screws for their shear/hanger products.
Correct me if I'm wrong, but aren't pocket hole screws only #8 in size? I've snapped the shanks off #8's in shear applications, the way they are made gives a very thin shank to resist the shear loads. That's why I only like #9 or #10 sizes.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Captain America! I command you to... WANK!
Edited 7/12/2007 12:19 pm ET by xxPaulCPxx
Check McFeely's, he has suitable screws for pocket hole work in #10, in stainless if you wish.
For teh simpson do a google for simpson strongtie screw.
Forgot to add a picture to that last post:
View ImageRebuilding my home in Cypress, CA
Also a CRX fanatic!
Captain America! I command you to... WANK!
Check out grkfasteners.com for some samples of structural screws. Pricey but good, roughly 10x the price of nails, not counting labor.
I will sometimes frame with screws to avoid cracking plaster on the other side of the wall from where I am working.
Jim
Never underestimate the value of a sharp pencil or good light.
depends...
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Piffin must be gettin tired tonite, you almost got him going.
Screws can be if they are of sufficient size and grade of material. Drywall and deck screws definitely are not; they are brittle and not especially strong. Even if they appear to hold when installed, shock loading or cyclic loading, such as from weather or a natural disaster can fracture them.
meadordite,
Screws have a great deal of strength if used properly.. Fine Home Building printed an article about their relative strength and clearly they are superior to nails..
a classic case..
Put a roof rafter on with the proper nailing schedule and it takes 208 pounds of force to remove the rafter from the top plate.
Improperly install a 3/8ths inch lag bolt and it takes 2,783 pounds to remove it. (the rafter wood fails before the slag screw gives up) ..