notched stair stringer question...
notched stair stringer question...
(OP)
Suppose you are calcing some exterior wood stairs, built the traditional way- (2) 2x12 stringers, notched, resulting in a remaining depth of 5-1/2".
I've never been sure what adjustment factors to use, and NDS literature seems to indicate that we are not allowed to notch a bending member more than 1/6 the depth, which would mean we simply cannot build stairs this way. Also, I have spoken to someone at AWC about ripping members, and he informed me that once a member is ripped, it must be regraded before we can know what allowable stress to use. Our notched stringer is quite similar to a 2x12 ripped down to 2x6 dimensions, but with some extra bits above which hold our treads where we want them...
But contractors always build stairs this way, and I would like to accomodate them... so any advice would be appreciated.
Cheers!
I've never been sure what adjustment factors to use, and NDS literature seems to indicate that we are not allowed to notch a bending member more than 1/6 the depth, which would mean we simply cannot build stairs this way. Also, I have spoken to someone at AWC about ripping members, and he informed me that once a member is ripped, it must be regraded before we can know what allowable stress to use. Our notched stringer is quite similar to a 2x12 ripped down to 2x6 dimensions, but with some extra bits above which hold our treads where we want them...
But contractors always build stairs this way, and I would like to accomodate them... so any advice would be appreciated.
Cheers!





RE: notched stair stringer question...
Another trick, if possible, is to provide a mid-span 2x4 stud cripple wall to cut the span in half.
RE: notched stair stringer question...
What may happen is that the 3" to 4" knot or 3" hole, that is allowed in your 2x12 may end up in the unotched area. So instead of having a section equivalent to a 2x6, you might have a section equivalent to a 2x4 or even a smaller section.
I believe one of the reasons, the use of notched 2x12 worked so well in the past was because of the higher level of craftsmanship. In the past I think builders culled out more material. When building a stair stringer they probably selected 2 x 12's which would have mainly clear wood in the unotched section. I am sure some of the framers today if given a notched 2x12 with a 2" hole, would use it. In the past I think most builders would have tossed such a piece aside.
RE: notched stair stringer question...