boltsjoistslumberwasher
I am fitting some new joists in my roof and will be bolting the new joists to the existing rafters. Both joists and rafters are 47mm thick.
After some advice from a friend (which may of course be incorrect!) I plan on using M12 x 110 hex bolts and timber connectors in-between:
My problem is I am unsure which combination of nut & washer to use. Some possibilities:
Which is best?
I guess I'm curious why you wouldn't simplify the layout like this:
Yellow = deck joists
Green = support beams
Your decking would run diagonally over the joists. If you use 2x boards for decking, that should be fine if the joists are 16" on center. If you want to use 5/4 decking, you should probably put the joists 12" on center so that the diagonal run is closer to 16".
If there was only one washer, it generally will go on the nut side as the nut has less surface area in contact with the thing being connected than the bolt side.
Best Answer
The spikey washer needs to go between pieces of wood. I doubt its usefulness, since the strength is either going to come from the bolt in shear, or friction between the wood surfaces, depending on how tightly it's bolted. The teeth won't fix poor clamping.
A lockwasher needs a lot of compression to function properly, it's really intended for metal. If backing off is a concern, use the nylok or a second "jam" nut.
You'll want large metal washers against the wood on both ends, otherwise the bolt heads will just sink into the wood when you try to torque it down.