• 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

Solid Sheathing and Asphalt Shingles

akabob

akabob

Member
Joined
Aug 17, 2010
Messages
4
Location
Montana
Can anyone give us their definitions for “solid” and “tightly Fitted” lumber roof sheathing? These two descriptions, along with “Skip Sheathing”, are referred to in the IRC and the IBC… but there are no definitions.

Where we’re having an issue is for a reroof with asphalt shingles. Both the IRC and IBC call for asphalt shingles to be installed over solid sheathing. What does that mean? I know that lumber sheathing is acceptable… how tight does lumber sheathing have to be for it to be considered solid sheathing? How big a space can “tightly fitted” lumber sheathing have between each board before it’s considered skip sheathing?

What are your requirements for solid lumber sheathing intended to support asphalt shingles?
 
I like to see no more the 1/4" spacing, with another 1/8" tolerance occaisionally. Otherwise install new sheathing. But, that's just me, like you said, it's not defined.
 
Last edited by a moderator:
akabob,

Welcome to the forum. Hope you stay and become a part of our group. Your questions are most easily answered if we know what State you are in; and which specific code book (and section if you have it) you are refering to.

"“solid” and “tightly Fitted” lumber roof sheathing. These two descriptions, along with “Skip Sheathing”, are referred to in the IRC "

I didn't see them in the 2006/2009 IRC Section R803. Where are they in the IRC?

Uncle Bob
 
Last edited by a moderator:
I do not have a current IRC but spaced sheathing is identified/defined in the IBC

IBC 1507.9.1 Deck requirements. Wood shakes shall only be used on solid or spaced sheathing. Where spaced sheathing is used,

sheathing boards shall not be less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners. Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) o.c., additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards.

“Skip Sheathing”, is one of those construction SLANG terms
 
Last edited by a moderator:
= + = + =

akabob,

Welcome to The Codes Forum! This forum is ' THE ' place to be! ;)

All from the `06 IRC:

See Table R503.2.1.1(1). Also, see Note ' C ' - "Applies to panels

24 inches or wider". Note ' D ' addresses the ' H type ' clips

between the sheathing panels. Typically, around 1/8" inch - - see

the imbedded link.

http://www.tecotested.com/techtips/pdf/tt_edgeclips

Table R803.1 gives the minimum thickness of sheathing.

Section R907 addresses Reroofing.

See the links for pictures of ' skip type sheathing '.

http://www.armstrong1234.com/shingle-process/5a.jpg

and

http://www.google.com/imgres?imgurl=http://4.bp.blogspot.com/_jINTM19DHx0/SxyBv4mCaAI/AAAAAAAAATI/MSo-6gNGv6E/s400/top%2Bof%2Bthe%2Bbarn.jpg&imgrefurl=http://ostmanfarm.blogspot.com/2009/12/appeasing-nisse.html&usg=__XszkS1q7F4SLFZMdGQYzCJb4lMg=&h=360&w=270&sz=21&hl=en&start=19&zoom=1&um=1&itbs=1&tbnid=ms1pVEntjdI2pM:&tbnh=121&tbnw=91&prev=/images%3Fq%3Dskip%2Bsheathing%26um%3D1%26hl%3Den%26sa%3DX%26tbs%3Disch:1

Hope this helps!

+ = + = +
 
Last edited by a moderator:
akabob,

install the comp per manufacturer's installation instructions .they will include the roof decking requirements. most manufacturer' state lumber sheeting should be tightly fitted boards that are a maximum 6" wide. i approve reroofs over 1x12 if the wood is still sound and no gaps over 1/4".
 
Howdy from Montana-

Thank you all for your welcome to the forum, and also thank you for your responses to my question.

Currently we are using the 2006 IRC. We recently adopted the 2009 IBC. The 2009 IRC is on hold for the moment due to issues regarding residential fire sprinklers.

The code sections I was refering to were, IRC R905.2.1 and IBC 1507.2.1. Also, IRC R905.4.1. From those sections, my old carpenter brain translated (without me noticing) "closely fitted" to "tightly fitted", and "spaced sheathing" to "skip sheathing". Opps. Sorry. That's a bad thing to let happen when you're quoting code sections.

This has only recently become an issue... we had a pretty good hail storm a month ago that damaged thousands of roofs. We've got roofers coming out of the woodwork trying to cash in on the roofing boom before winter sets in.

We are trying to clarify the code requirements for the insurance companies who don't want to pay for putting plywood or osb over an existing/older roof structure with spaced sheathing in preparation for asphalt shingles.

I know in my mind what all of these different types of roof sheathing look like... but because I'm being asked to set policy and interpret what the code is actually requiring, I thought it would be good to get input from others on the question... this seemed like the perfect place to do that. I discovered this forum recently when I found a link for it in the new ICC discussion forum.

I actually asked for a definition from ICC regarding the different sheathing types and they were unable to provide them. So here I am.

Thanks again for your help with this.

Bob
 
Last edited by a moderator:
Bob,

"We are trying to clarify the code requirements for the insurance companies who don't want to pay for putting plywood or osb over an existing/older roof structure with spaced sheathing in preparation for asphalt shingles."

If the roof has "spaced sheathing" (R905.7.1) with 1" X 4"s spaced, for wood shingles and/or shake; and the owner wants to change to asphalt shingles; then, the roof must be fully, "solidly" sheathed (R905.2.1); for example with plywood or osb sheathing. Installing asphalt shingles over the open spaces between the 1" X 4"s, is not an option.

Some confusion may come from the difference between "spacer clips" to allow for expansion and contraction between sheets of plywood or osb sheathing; and " spacing" between 1" X 4" strips for wood shingles (905.7). Totally different kinds of spacing.

The insurance company "knows the code requirements"! The agreements between insurance companies and owners; is not relevent; and the Building Safety department should not become involved with any disputes conserning that agreement.

The asphalt shingle manufacturer will also not warranty the shingle if not attached to code and/or manufacturer's sheathing requirements.

Uncle Bob
 
Last edited by a moderator:
Welcome to the board judging by the leaf less trees in the background I would guess you may be an eastener and this seismic requirement may not be applicable

R803.1 Lumber sheathing.

Allowable spans for lumber used as roof sheathing shall conform to Table R803.1. Spaced lumber sheathing for wood shingle and shake roofing shall conform to the requirements of Sections R905.7 and R905.8. Spaced lumber sheathing is not allowed in Seismic Design Category D2.

FWIIW

Skip Sheathing

The normal base for shake, shingle and some tile roofs. 1" x 4" or similar sized boards are nailed at 90 degrees to the rafters leaving a space of about 4" between each row and allowing for better ventilation.
 
"Can anyone give us their definitions for “solid” and “tightly Fitted” lumber roof sheathing?"

Usually the boards are laid tight together - without the 1/8" spacing that is normal on decks. The boards dry and shrink. The resulting gaps are ok.
 
George, what do you feel is an exceptable "resulting gaps" in the realm of installing asphalt shingles?

Serious question, I am interested in your response,
 
6" wide boards are not going to shrink more than 1/2". 1/2" might make nailing a pain in the neck, but it will not change how long a roof will last. I guess I would prefer gaps to be less than 1/2", but I don't see how 1/2" gaps will harm the roof.
 
Thanks, supports my opinion of 1/4" typical to 3/8" max.

Back in the day, about 25 years ago, I installed asphalt shingles on a 10/12 roof that had 1 1/2" to 2" spacing. Like you said, pain to nail, surely voided any warranty on the product, but got it done, looked good, and did for years to come.
 
If I may, I'd like to hijack and steer in a slightly different course. Assuming the rafters are capable of supporting the loads, and assuming proper ventilation is provided, would you allow new solid sheathing and shingles to be installed over the top of one layer of wood shakes?
 
I don't think I would allow it. How is it going to be fastened? Even with 16d nails, you wouldn't have much fastener penetration after going through 1/2" decking then a layer of shakes, which would be what, another 2" typically? Don't think so, unless they could get an engineer to buy off on it.
 
I would go with the 3/8 inch max after the wood shrinks for board sheathing.'

NO the new plywood cannot be put over old wood shingles--too much dead load and no way to properly attach.
 
I'll quit after this question, because obviously this is of little interest, but: §R907.4 (IRC2006) says that if "...new roof covering over wood shingle or shake roofs creates a combustible concealed space, the entire surface shall be covered with gypsum board, mineral fiber, glass fiber, or other approved materials securely fastened in place". As described in my earlier question, if a wood shingle roof were to be sheated over with new decking, would that create the "combustible concealed space" refered to in this section, even though it would not be one, continuous concealed space, but rather a series of very small concealed spaces?
 
Code Neophyte said:
If I may, I'd like to hijack and steer in a slightly different course. Assuming the rafters are capable of supporting the loads, and assuming proper ventilation is provided, would you allow new solid sheathing and shingles to be installed over the top of one layer of wood shakes?
Click to expand...
Not in my AHJ, especially if you live in a wildland interface area.

CBC requires a complete tear-off if you are changing roofing materials and additional restrictions are also placed on what type of materials are allowed on roofs in high fire areas.

Sue, in sunny CA
 
You must log in or register to reply here.
Top