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Re: sistering a new joist
function wrote:

Sorry if it seems like I was baiting, I like to gather knowledge from many sources, and the experienced contractors and others here are great for me as my background is insurance and DIY.
If anybody out there has questions about their worker's comp insurance for their contracting company, I'm glad to help from that end.

It's good to know your line of expertise and thanks for offering free advice to whomever needs it.

Re: sistering a new joist

I really don't see that 4x4 providing much support, I'm guessing that you don't have blocking between the joists and that is why it is there. But to answer your question, yes you can, BUT, now the fastening system does become critical and deck screws will not cut it.

If you do that, I still recommend the construction adhesive and at least 6 bolts (1/4-20 4.5" long) with oversized washers. Use a triangle pattern of three on each side of the bad section. The main reason for this is to clamp the two boards together while the adhesive is drying.

Then nail or use 1/4" hex head wood screws about 3" long to finish. If you don't have a nail gun, you will find it really hard to swing a hammer with only 13" of clearance. That only leaves an arc of 9.5", can't get much momentum up in that short of a swing.

You need a right angle drill to drill the 1/4" holes for the bolts too.

Re: sistering a new joist

According to Tom Silva, you should glue and nail sistering joists. Normal screws are too brittle and can break, though I wouldn't be concerned as much with a soft enough screw. With a properly sized sister, it supports only itself and what is above it plus the original as far as how well it is bonded to it So if the load is only on the original, that bond becomes crucial but if the sister goes under the load it becomes less critical.

In my mind you don't take chances with structural members so you use the best method or you might be redoing the job. I've never seen a structure fail from being too strong- have you?



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