Undersized Purlins

[William M. Fossier Jr.]

Sorry: I posted in wrong area.

I recently did a builder's home where the purlins are smaller then the rafters. Should I call this a repair or just note it. The home was built in 2000 and we are in Texas. Is there an exception to standards.

Thank YOu

[Barry Adair]

I answered here

[Richard W. Washington]

Purlins and purlin supports should be no smaller than the rafters they support at least from 2000. 2000 IRC 802.5.1

[Kenton H. Shepard, CMI]

It's like confiming that something is built according to plan or to the engineer's specs, can't do it. I have no problem with a purlin which is smaller than the rafters. A 2x8 or 2x10 purlin under 2x10 or 2x12 rafters is fine as long as it's adequately braced.
I like to see 2x6 purlin braced every 4 ft. It really depends on the rafter span.
2x4 purlins are common in older homes around here and they aren't great but they're a lot better than nothing and that's what I tell people verbally but I don't mention them in the report unless they have visible failure. If 2x4 purlin has held up with no failure for 50 years, I'm not going to call it out as being in need of repair.

I call it out as inadequate if I see signs of failure, like sagging rafters or purlin.

[Richard W. Washington]

If the home was built in 2000 though a 2x6 rafter must be purlin braced by doubled 2x4's, with likely a 2x6 purlin. Most purlin framed system homes in Texas are braced that way.