• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Roof Decking

Uncle Bob

Uncle Bob

Registered User
Joined
Oct 17, 2009
Messages
1,409
Location
Texas
I have been getting inquires about adding a layer of 3/8" osb over lumber roof decking. The inquires come from what is reported to be a requirement of the asphalt shingle manufacturer that you cannot have over a 1/4" gap bettween the decking boards. We recently had a hail storm and many of the homes are being reroofed. My first thought is remove the boards and redeck the roof. Could roof loads be a factor? Engineering required to add load? Has anyone worked with this type problem or request? How do you handle this type of inquiry? Thanks, Uncle Bob
 
I haven't seen 3/8" used in a new application....it is always 1/2"...it hasn't been an engineering problem. I have seen plenty of old roof sheathing that is 3/8" plywood. It is my understanding that the shingle makers require a minimum 1/2" sheathing.
 
Last edited by a moderator:
I agree with mtlogcabin too!

I think GP and LP OSB require a 1/8" gap but not sure if its needed when laying over an existing lumber roof deck. I think the sheets may allow for the gapping and don't measure exactly 4x8.

pc1
 
Put 7/16 over rough sawn 1x on my roof. Nailed through 1x to framing, screwed to 1x where it didn't hit. Less dead load than a layer of roofing. The space as per manufacturer to avoid joints from raising due to expansion
 
You must log in or register to reply here.
Top