# Roof Sheathing



## Lynell (Mar 1, 2010)

2006 IRC  Sheathing next to peak of roof is it a min. of 24 inches?


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## mtlogcabin (Mar 1, 2010)

Re: Roof Sheathing

TABLE R503.2.1.1(1)

ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF

AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c

c.	Applies to panels 24 inches or wider.

If it is not 24 inches then it would not meet the presrciptive requirements of the IRC


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## Lynell (Mar 1, 2010)

Re: Roof Sheathing

Thanks! Mtlogcabin, That was my thought just need reassured I guess.


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## north star (Mar 1, 2010)

Re: Roof Sheathing

*Lynell,*

*Welcome to the codes forum!   *


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## TimNY (Mar 2, 2010)

Re: Roof Sheathing

Just so I have this clear in my head..

Would this be a scenario where the builder started laying sheathing at the eaves and when he got to the peak had to rip a strip to 12" wide to finish up?

or

Where a contractor starts laying at one rake, and when he gets to the other rake needs to rip a 16" wide strip to finish?

or

Both?

Thanks,

Tim


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## GHRoberts (Mar 2, 2010)

Re: Roof Sheathing



			
				mtlogcabin said:
			
		

> TABLE R503.2.1.1(1)If it is not 24 inches then it would not meet the prescriptive requirements of the IRC


I believe that the code section is there to prevent one from using strips less than 24" (nom) to cover the entire roof. (I have a copula with a hip roof. It violates that code section - the copula roof is not 24" from peak down.)

As I recall the APA website has formula that give the allowable loads on narrower pieces of plywood.


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## Uncle Bob (Mar 2, 2010)

Re: Roof Sheathing

I'm unclear on what's happening here; but, are ya'll stating that dimensional lumber or tongue and grove usually 4- to 8-inch wide boards that  are nominally 1-inch thick (3/4-inch actual thickness) is not allowed to be used for roof sheathing?

It's my understanding that the only reason builders went to plywood and/or OSB; is because it's cheaper to install.

What am I missing here?

Uncle Bob


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## bldginsp (Mar 2, 2010)

Re: Roof Sheathing

Uncle Bob, I believe what these fella's are refering to are for structural panels only.  This code section does not include dimensional lumber.


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## globe trekker (Mar 2, 2010)

Re: Roof Sheathing

Uncle Bob,

I agree with bldginsp!    I believe that the OP was referring to the osb type roof sheathing that is typically

"cut-to-fit" when they get to the roof ridge.    Not compliant mind you, but that's just pretty typical.

At least until Uncle Bob sees it and makes them rip it out and install it correctly.    

.


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## Uncle Bob (Mar 2, 2010)

Re: Roof Sheathing

Globe, & BldgInsp,

Thanks, I checked 803.1, and found that they can still use the "good stuff".

Uncle Bob


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## Anders (Mar 10, 2010)

Re: Roof Sheathing

great post great info.


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## peach (Mar 10, 2010)

Re: Roof Sheathing

of course you can still use "the good stuff", UB..   

If you use a ripped sheet of Plywood or OSB (especially at the ridge, eave or edges), you'll want to block between the rafters (or trusses), so you have a nailing surface for the sheathing... or you could have uplift issues.

Depends on how you propose to piece it in...


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## reelone (Mar 15, 2010)

Re: Roof Sheathing

How would you sheath a hip roof ?


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## Uncle Bob (Mar 16, 2010)

Re: Roof Sheathing

Reelone,

You just keep cutting them shorter as you go up.  Some of the builders around here use 1by; I'll take a picture.  A long, long time ago, when we used 1by for subfloors on pier and beam; we always started in a corner and worked our way diagonally across the floor joists.

Uncle Bob


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## Glennman CBO (Mar 16, 2010)

Re: Roof Sheathing

What is "the good stuff"...?

I had a neighbor (back when I lived out in the sage brush sticks) that had a west facing wall (the weather side) that had OSB exposed on it for at least 14 years. The surface was a bit "flaked" but overall it looked pretty good. I doubt that plywood would last as long. No offense to plywood lovers.


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## Pcinspector1 (Mar 16, 2010)

Re: Roof Sheathing

I believe plywood clips can be used in some applications where the plywood is cut under 24" in width (a strip at top ridge area is real common to see)


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## JayHawkInspector (Mar 16, 2010)

Re: Roof Sheathing

I have a unique question; what if you have a four inch piece at the ridge, how good would the nailing of the ridge cap shingles? Even if you have clips in this situation the nails from the ridge cap shingles would be right into the joint.


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## Mule (Mar 16, 2010)

Re: Roof Sheathing



			
				Lynell said:
			
		

> 2006 IRC Sheathing next to peak of roof is it a min. of 24 inches?





			
				mtlogcabin said:
			
		

> TABLE R503.2.1.1(1)ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF
> 
> AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c
> 
> ...


This is not what Lynell is referring too. Lynell is referring to "how tall" is the top strip required to be. This section of the code refers to the width.



			
				TimNY said:
			
		

> Just so I have this clear in my head..Would this be a scenario where the builder started laying sheathing at the eaves and when he got to the peak had to rip a strip to 12" wide to finish up? Tim


No. It is okay to have a strip less than 24" tall.



			
				TimNY said:
			
		

> Where a contractor starts laying at one rake, and when he gets to the other rake needs to rip a 16" wide strip to finish?Thanks,
> 
> Tim


This is where the width needs to be a minimum of 24"



			
				peach said:
			
		

> If you use a ripped sheet of Plywood or OSB (especially at the ridge, eave or edges), you'll want to block between the rafters (or trusses), so you have a nailing surface for the sheathing... or you could have uplift issues.Depends on how you propose to piece it in...


Uplift issues???? I thought this is what collar ties or ridge straps are for!

And as far as hip roofs, I believe as long as the bottom triangle portion of the OSB is 24" then all is well because you have the entire hip to nail the OSB to up the edge of the triangle.

These are my opinions.


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## peach (Mar 16, 2010)

Re: Roof Sheathing

Think of high winds as a vacuum cleaner sucking the roof up.  If the sheathing isn't properly nailed (which includes blocking).. the roof sheathing will fail (and therefore.. bye, bye roof)


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## Pcinspector1 (Mar 17, 2010)

Re: Roof Sheathing

OP, said peek not ridge, is this the triangle piece on the gable sidewall he is calling out as a peek or is it the ridge on the roof he is calling the peek?

Happy paddy day! : :mrgreen:


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## GHRoberts (Mar 17, 2010)

Re: Roof Sheathing

mule wrote "This is not what Lynell is referring too. Lynell is referring to "how tall" is the top strip required to be. This section of the code refers to the width."

The APA load capacities are based on how wide ("tall") as plywood strip is.

The length of the strip also needs to have 3 bearing points.

But I think too much attention is being paid to this issue.


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## JBI (Mar 17, 2010)

Re: Roof Sheathing

George, you're probably correct... on all three counts.

IMHO, if you need a 12" strip of roof sheathing at the top of the roof plane, you didn't lay out the job properly. If you need to place a 16" strip at the rake, you didn't lay out the job properly.

But that's just my opinion, and opinions will vary.


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## north star (Mar 17, 2010)

Re: Roof Sheathing

*But John,  you know that `ol Paco and his crew `no habla Englais!    What codes... ?*

*What dimensions... ?   * 

*Also, how many code officials on here have actually made a fine, upstanding builder*

*in that community, ...who is paying their [ the code officials ] salary, ...who is*

*providing jobs in that community, ...who is providing a needed service in that*

*community, ...who has been doing it that way for 40 yrs. and never had any*

*problems,  [ said "tongue in cheek"   *  * ] tear the roof decking off and re-do it*

*correctly, or to install additional approved type fasteners [ nails or screws ] in to*

*that "less than code compliant" roof decking strip,  or as peach mentioned,*

*actually install the correct type of blocking?*


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## peach (Mar 17, 2010)

Re: Roof Sheathing

doesn't have to be at the peak or ridge or edge... any piece that's not secured on all edges is liable to fail ..


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## Pcinspector1 (Mar 19, 2010)

Re: Roof Sheathing

peach,

You are correct in your analysis. HD does not sell #5 sky hooks anymore, I checked! :roll:


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