Home Repair

What is the difference between through bolting and lagging?

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I read your comments in another article on the site about attaching a ledger to a house for a deck:
TheGuru wrote:
Most towns require through bolting for the ledger rather than lagging. So ask your building department.
So, what is the difference between through bolting and lagging?

Thanks, Guru!
If you drill a pilot hole and put a lag bolt into the rim joist or into the sill plate, that would be lagging. A lag bolt looks like a giant screw with tapered threads and a hex head.

Through bolting is when you drill a clearance hole all the way through the material, the siding, the sheathing and the rim joist. Slide a carriage bolt all the way through, put on a washer and a nut, then tighten with a wrench. A carriage bolt has machine threads and the head is round with a square area underneath. This square spot will grab into the round hole and keep the bolt from turning when you tighten the nut on the other side.

Remember the siding needs to be cut away and flashing installed, or small blocks made from upside down shingles put where the bolts are. Otherwise the ledger will be tilted on the siding.


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