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01-11-2011, 07:23 PM #1
Hello to all, this is my first post (new member). i am a new inspector down in Houston,Tx. My question is in regards to purlin requirements. I have inspected a few homes where purlin boards/support appeared to be missing! What is the code requirement for purlin installation? I know the size recommendation i.e. rafters. Do all roof structures need purlin support? Please see photo!
01-12-2011, 08:30 AM #2
This will partially answer your question: http://www.inspectionnews.net/home_i...e-purlins.html
Added rafter support (e.g. purlins) is only required if the rafters can not span the entire distance on their own, kind of like determining whether another beam is needed for proper deck support.
01-12-2011, 10:11 AM #3
Steve always look at a roof from the out side and the inside.... 99% of older roof will have some kind of a dip in the roof line at one point or another.
If you can see a dip in the roof you should point that out in your report.
01-12-2011, 10:26 AM #4
Re: purlinsScott Patterson, ACI
Spring Hill, TN
01-12-2011, 01:47 PM #5
By the looks of that attic I would say that the 2x6 rafter is a minimum of 12 to 16 feet long. 12 feet is a pushing it to have acceptable deflection. 16 feet is way to far. High winds coming up through the eves and the roof bouncing in the wind could easily pull that roof of in a sustained higher wind. Wlaking on them over 12 feet long is stretching it as far as cracking one. It is not always something in a book that tells you to write something up. Just explain the condition you found while inspecting.
01-12-2011, 02:35 PM #6
Re: purlinsJim Luttrall
01-12-2011, 03:10 PM #7
Here's a clickable link to the American Wood Council's joist & rafter Maximum Span Calculator (its set to default with #2 SYP but you're free to change any of the settings and values): Maximum Span Calculator for Joists & Rafters
Last edited by H.G. Watson, Sr.; 01-12-2011 at 03:28 PM.
01-12-2011, 03:23 PM #8
Kinda goes hand in hand...I know, I know...proper terminology.
In any case bounce on the roof. If you have lots of bounce..no good. If rafter cracks or breaks, no good. A lot of sag when stepping directly on the rafter, no good. The roof should feel nice and stiff. I doubt it does as it is.
If in fact it is a least 12 feet and I do believe it is that or more, it needs support seeing how it is a 2x6
01-12-2011, 03:31 PM #9
Ted, rafter spans are determined horizontally.
01-12-2011, 04:23 PM #10
01-12-2011, 05:20 PM #11
HG is just a stickler on terminology. Yeah he is right but anything crossing an open area, trench ditch, top plate to ridge, one side of the river or another, spans that void, expanse, whatever but also has a particular length to it. I know why he is saying it and I also Know HG.
Use the term that fits the item one is referring to.
I got it HG
01-12-2011, 05:57 PM #12
He's absolutely right, span of a rafter is not measured ridge to wall, but I'm surprised HG called it out so civilly! I was commenting on his change of attitude, not his correction. Nothing wrong with correcting a mis-statement if it is done politely.