What thickness lag bolts should I use?

Question

I am building some stairs for a church and it needs to be pretty durable and be able to hold significant weight 12 people. Any ways, I am using 4 x 6 's and I was wondering what should the diameter of the lag bolt be to hold some weight?

Answer 1

B.Hog is correct.  For standard residential stairs I use 3/8", but for commercial I would definitely step up to 1/2"  Predrill the hole 5/16", then run the lag in.  Be sure that you have at least 1-1/2 to 2" of penetration.

Answer 2

1/2" will do it

Answer 3

1/2" will do.  Make sure they are long enough and in the right place to bite on solid wood inside the wall you are attaching to.  You'll want two lags one above the other every 18".