I've got a short load-bearing post that sits on a 12" deep glulam header, connected by angle brackets (HL55's). What length 1/2" lag screws should I use to attach to the glulam (going perpendicular to the planes of the glued layers?). I'm guessing too short and it doesn't hold well, too long and the seasonal swelling will eventually cause the threads to lose grip? The header's already shrunk an 1/8" in the hot, dry Sierra Nevada Summer despite being nominally dry on arrival.
Also, I'm gonna be dropping in my main 30ft x 6 3/4" x 18" beam in a week or so (with the help of a crane). Should I pre-drill the bolt holes for the CC67 column caps or drill them once it's sitting in place?
FYI, the beam cost $530 inc. CA tax, a crane (from the local truss company) is $130 hour with driver, minimum 2 hours, with most of the time being spent driving to the cabin. CC's are about $75/piece ex. tax, 3 needed, with maybe $15 of bolts in each one. So somewhere around $1100 all-in to buy and install the one piece of wood!
Looking in the NDS, min penetration is 8diameters so a 4-1/2" screw min. Pilot a full 1/2" for shank portion and lead hole full depth 60-75% diameter.
...
Checking the AITC manual, the glulam manual,
1/2" shank clearance hole, for group II (I'm assuming you have dougfir) 5/16" lead hole soap or wax lube is suggested
Lateral;
4" with 1/2" steel plate-610 lbs parallell to grain, 320 perp to grain
5"-840, 440
6"-950, 490
7"-970, 500
8"-980, 510
9"-990, 510
more additional length does not increase lateral strength
withdrawal in .49 specific gravity wood, 1/2" lags, 367 lbs per inch of penetration
My Simpson beam seats and column caps came with the SDS screws. They say no predrilling needed, but I used soap when I put 'em in with a 3/8" drive air impact (very carefully so as to avoid stripping!)
Fasteners less than 3/8 dia in withdrawal are not required to be piloted :)
Quote from: Don_P on July 14, 2009, 09:06:09 PM
Looking in the NDS, min penetration is 8diameters so a 4-1/2" screw min. Pilot a full 1/2" for shank portion and lead hole full depth 60-75% diameter.
...
Checking the AITC manual, the glulam manual,
1/2" shank clearance hole, for group II (I'm assuming you have dougfir) 5/16" lead hole soap or wax lube is suggested
Lateral;
4" with 1/2" steel plate-610 lbs parallell to grain, 320 perp to grain
5"-840, 440
6"-950, 490
7"-970, 500
8"-980, 510
9"-990, 510
more additional length does not increase lateral strength
withdrawal in .49 specific gravity wood, 1/2" lags, 367 lbs per inch of penetration
Thanks for all the great info - yes, it is DF. It looks like 6" screws are the way to go.