Can a 20' 6x12 rdwood be safely supported by 2 redwood corbels at each end 17'apart?
Question:This is for an arbor over a 16' garage door. The house is stucco'd and there's 5 1/2" of foam trim around the door, so the closest I can get the corbels mounted is at 17'. They're 6x10 or 6x12 corbels. They're bulged at the bottom and end to end they're 31.5" with about 7" of landing at the wall end as well as at the top. If this is possible, can these simply be lagged-in thru the stucco and into the wall? I think there's 6x's in therenext to the kings. There will be a 2x12(20')ledger lagged into the gar. header and 4x4s laying across the top at 16-20 in. on center. Any help guys, please and thanks.. Is 7" 3/8 lag-screws enough? Maybe little clips on the side? It just doesnt seem like this will work.
Answers:
red wood is a soft wood eventually the lags will pull threw the cor-bell your better off using L brackets to secure the beam then cover the brackets with a false cor-bell even then i think it would sag over time.
I wouldn't do it. You need more structural support. You are seeing this first hand not me. If you are already questioning the stability then make some different plans. Don't chance it. Do it right the first time.
The question needs additional information. What is the arbor weight on the 6x12? this load is transfered to the corbels. The corbels should be anchored to the wall (I'd specify through bolts w/ blocking between the studs. More importantly the edge distance for the fasteners into the corbel.
Parallel to grain loading is 7 diameters minimum edge distance, perpendicular to grain loading is 4 diameters.
You might want to consider knee braces in lieu of corbels.
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