# sheathing blocks instead of h-clips, help needed



## roof52 (Apr 8, 2012)

Hi everyone, I need some help here. I just had my roof replaced (tear off) by one of the best roofing contractors in my area. They are A+ rated by the BBB and have GAF certification. I have a gable roof with roof trusses 24" o/c and 3/8 plywood sheathing with h-clips. The roofer replaced all the sheathing along the ridge, but didn't install h-clips on the new sheathing. After researching this, I've found that blocking can be installed at the sheathing seams in place of the h-clips. I have some concerns about this, such as: How exactly is this blocking accomplished (a picture would be very helpful), is adding blocking a good substitute for h-clips, even if the blocking adds support to the sheathing, it doesn't do a thing for the expansion and contraction issue. The replaced sheathing on the ridge of my house was less than a full sheet of plywood and is only about 10" wide. I've read:huh: the narrow sections of sheathing required more support than full sheets, thus multiple h-clips are recommended on all sides. What would be the best course of action to take for area?

I want to resolve this with the roofer but I DO NOT want my roof to be compromised because of an error made by the roofer. Should I demand that he tear it all off and do it over correctly using h-clips? Thank you


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## gregzoll (Dec 25, 2006)

Just because the BBB states that they have a A+ rating, there is information out there to show that the rating can be bought. Also any roofing contractor out there can be GAF certified. If they did not install the clips, and they are required as stated by your AHJ, I would be having the contractor come back and correct it. But first having your city inspector look at the workmanship and state if it passes or fails their inspection, so that you have something to go on, plus the city can play hell on the contractor if they really want to. But on the offside, it can cause headaches for you if they give you a Red tag. First I would go and talk to the AHJ before having an inspector come on site. Also are permits required by your AHJ before tear off, regardless who does it?


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## joecaption (Nov 30, 2011)

I would never ever use 3/8 sheathing on a roof, to thin and not rated to span 24". A bare minimum would be 1/2. Only time I've seen it used that thin is on mobil homes and cheap sheds.
I also would never install a piece along that edge less then 24" wide.
With 24" spans you must use H clips. It would take way to long to do the blocking and your right it would not preset the spacing needed.


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## roof52 (Apr 8, 2012)

Hi gregzoll,

I'm not familar with the initials AHJ, and there is no permits required for any type of roofing in my area. And even when the city requires a permit, they will NOT act on your behalf to force a contractor to correct their work. They will just simple not approve the work and it's entirely the responsibility of the homeowner to get the work corrected so that it received the approval from the city.


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## roof52 (Apr 8, 2012)

Joe caption, thank for your reply. 3/8 sheathing 24"o/c center meets all codes here in upstate NY. What's the issue with a narrow width of sheathing at the ridge? Can you explain exactly what this blocking consists of? and possible include a photo? So, are you saying I should demand that he tear it all out and redo it using h-clips?


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## gregzoll (Dec 25, 2006)

AHJ = Authoritive Having Jurisdiction (ie City hall permit/inspection office/regulatory dept.).


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## gregzoll (Dec 25, 2006)

roof52 said:


> Joe caption, thank for your reply. 3/8 sheathing 24"o/c center meets all codes here in upstate NY. What's the issue with a narrow width of sheathing at the ridge? Can you explain exactly what this blocking consists of? and possible include a photo? So, are you saying I should demand that he tear it all out and redo it using h-clips?


I would and do it at their costs if it is required. That is why I am glad that my roof decking is 1x6 boards, and there is only one area that is 3/4" Exterior rated plywood on my roof, but it is on a dormer that is the entrance to my home.

BTW, did they use any Grace Ice & Water shield for the first 3 feet above the gutters, then 30# felt, or just use the bare min? Can you post pictures of the decking from inside the attic, and from outside showing the workmanship? Especially around any penetrations such as chimney, flue, vent piping? Also, did they do proper venting on the roof, such as ridge venting if you have soffits?


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## joecaption (Nov 30, 2011)

http://osbguide.tecotested.com/pdfs/en/el807.pdf

3/8 Is the bare minimum to meet code.
Personaly I'd never use it on a roof with 24" spans.

Anytime I see a roof done with 3/8 sheathing it's all wavy from all the sagging between the rafters or trusses.
Trying to just get the nails into a narrow piece would not be much fun because of all the bouncing when trying to attach the shingles.


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## gregzoll (Dec 25, 2006)

Joe, even 1/2" is just as bad as 3/8ths. Min. should be nothing more than 5/8ths period, with OSB not being allowed. Even with Ply you have problems with it deteriorating as quickly as OSB if not covered properly.


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## Gary in WA (Mar 11, 2009)

Check to see if you are under the "I" Codes, they accept 3/8" sheathing (rated 24/0) or roof = 24" on center support rafter/truss, floor = not applicable. BUT, *24" o.c. require clips or edge support*; first chart, second column =3/8"----footnote "d"; http://publicecodes.citation.com/icod/irc/2006f2/icod_irc_2006f2_5_sec003_par004.htm

Without the support, you can span *maximum 20" *o.c. He needs to add 2x4 blocking, flat, directly under the joints of sheets, perpendicular to the rafters, tight to the sheathing.

Gary


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## Ravenworks (Oct 31, 2010)

gregzoll said:


> Joe, even 1/2" is just as bad as 3/8ths. Min. should be nothing more than 5/8ths period, with OSB not being allowed. Even with Ply you have problems with it deteriorating as quickly as OSB if not covered properly.


 Everything on my roof is 3/4" wouldn't have it any other way.


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## sixeightten (Feb 10, 2009)

In 30 years, I have only installed 3/4 on a roof once. 5/8 is a nice premium upgrade, most are done with 1/2" and perform just fine. 3/4" is overkill for no good reason in my opinion.


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## Ravenworks (Oct 31, 2010)

sixeightten said:


> In 30 years, I have only installed 3/4 on a roof once. 5/8 is a nice premium upgrade, most are done with 1/2" and perform just fine. 3/4" is overkill for no good reason in my opinion.


Ummm it was free is good enough reason to use it, I don't know the name of the product but it was red and designed as sheeting.


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## roof52 (Apr 8, 2012)

* GBR in WA*, Hi Gary, You stated "He needs to add 2x4 blocking, flat, directly under the joints of sheets, perpendicular to the rafters, tight to the sheathing"

Can you show me a picture or two of what this exactly looks like? This is what I invision. A 2 x 4 fitted between the 24" span of the truss, pressed tight against the sheathing edges and toenailed in place with 2 screws on each end of the 2 x 4 for a total of 4 screws per 2 x 4. Also, would it be advisable to use an adhesive sealer or glue in between the 2 x 4 and the sheathing? Does it matter if some of the sheathing has h-clips and some has blocking? What about expansion and contraction were the blocking is used? And as I said a picture of what this would look like would be very helpful. 

thanks roofer52


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## packer_rich (Jan 16, 2011)

I have done more than a few roofs with clips and there were times we used blocking. With a small rip, the size you mentioned, I don't think expansion and contraction will be a big problem. You should make sure the blocking is installed just as you said above.


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## roof52 (Apr 8, 2012)

Hi everyone, Can anyone post a photo or two of "blocking roof sheathing". I can't seam to find a picture of exactly what it looks like. Thank you


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## Gary in WA (Mar 11, 2009)

Just install the 2x4 with the 3-1/2" side tight and centered under the sheathing joint. No adhesive. The panels should be gaped for expansion, especially if OSB. 1/8- 1/4" gap. Read the printing on the attic side of the sheathing. Use nails (3") through the rafter/truss into the blocks. H-clips OR blocks, not both.

Gary


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## roof52 (Apr 8, 2012)

Gary, thank s for the clarification. The sheathing that were replaced do not have any gaps, so blocking the panels will only resolve one aspect of the missing h-clips (adding support to the sheathing between truss spans) but will do nothing about the expansion and contraction issue, right? This is what I was referring to when I mentioned using both h-clips and blocking. The roofer did use some h-clips on the replaced sheathing but on all of it. So were are talking about maybe 15 sheets of replaced sheathing and of that maybe 10 sheets do not have h-clips. If there are some 4 x 8 sheets of sheathing that have h-clips and some sheets that have blocking and some sheets have h-clips on one side and blocking on the other side, is that going to be ok?





Just install the 2x4 with the 3-1/2" side tight and centered under the sheathing joint. No adhesive. The panels should be gaped for expansion, especially if OSB. 1/8- 1/4" gap. Read the printing on the attic side of the sheathing. Use nails (3") through the rafter/truss into the blocks. H-clips OR blocks, not both.

Gary


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## Gary in WA (Mar 11, 2009)

First; check the ink stamp in the attic on the sheathing for the span rating and thickness. If 24/0, it requires; clips or blocking, one or the other, not both. Here is how to read it and what to look for; http://constructionmanuals.tpub.com/14043/css/14043_75.htm

As to “If there are some 4 x 8 sheets of sheathing that have h-clips and some sheets that have blocking and some sheets have h-clips on one side and blocking on the other side, is that going to be ok?”----- This is acceptable.

We can go from there.

Gary


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## dougger222 (Feb 25, 2011)

We rarely put h clips between osb or plywood when doing repairs instead we install 2x4's between the truss's at the seams. If we are pulling off all old decking and installing new then we will install h chips with OSB. 

If you have a parelled vault the 2x4 blocks may prevent air flow so in these cases you want to run h clips.

A framer turned roofer from hail I know goes inside homes with buckly plywood and puts 2x4's between all seams.

We've done hundreds of roofs with Plywood and OSB without h clips and no 2x4's.

IMO, OSB has better qualities than plywood. LP Smartside a siding product made to compete with James Hardi is OSB based and NOT plywood based.

The only plywood I like is 5/8in 5 ply.

At best the roofer may have to tear off and replace just the area were h clips were used. It would be better IMO to have him put some 2x4's under the seams...

BTW,
We've torn off a lot of roofs were the plywood or OSB without h clips was not gapped and 20-30 years later there's been no signs of issue. When we put OSB over spaced plank boards we don't gap them. Keep in mind the idea of redecking is to make a solid deck surface.


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## roof52 (Apr 8, 2012)

dougger222, thanks for your response. I have a few questions.

What is a parelled vault?

You said, "A framer turned roofer from hail I know goes inside homes with buckly plywood and puts 2x4's between all seams"

I believe you mean "buckled" plywood, right. If that is correct, what good would it be, to block seams that have already buckled.. The blocking only adds support to the roof sheathing and does nothing for buckling caused by expansion and contraction.

I also realize that sometimes a roofer can do all kinds of things wrong and the home owner may not have problems. But, if your paying for a proper roof replacement and it isn't done properly, the question should not be, will problems develop down the road. The only question should be, does the roofer tear off and correct the problems(as if they never happened) or does the roofer reduce his price by a dollar amount equal to what the home owner can hire an expert to correct the problems, plus 20% for his (home owner's) aggravation. Just my opinion.


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## dougger222 (Feb 25, 2011)

roof52 said:


> dougger222, thanks for your response. I have a few questions.
> 
> What is a parelled vault?
> It's a roof system that the trusses are the same as the top and the bottom. Cathederal may be another term. With this system you need to have open air flow of an inch or two under the decking to allow air to move from soffit to ridge vent. With this system you have to install ridge vent and can't do turtle or louvered vents. Putting 2x4's with this truss system will block proper air flow.
> ...


IMO,
The lack of h-clips in one little area of your roof won't do much harm. I'd be more nervous with 3/8in plywood 24in O/C!!! Never seen that before, been on thousands and thousands of roofs... To put a dollar amount on it? I don't know, a couple hundred. 

Last year ago I inspected the roof on a house for a buyer who's roof we just did. From the ground you could see buckly spots all over it. In the attic we found plywood and no h clips. The original builder hired a framer to go in the attic and run 2x4's on the really bad spot. Keep in mind the house was almost 20 years old and sold for about a million. The house we roofed that she moved out of was HUGE. She downsized...


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## roof52 (Apr 8, 2012)

I looked at the areas without h-clips and there are nails coming through the sheathing near the seams. I can't fit the 2 x 4 blocks up against the sheathing because the nails are in the way. I'm not sure what these nails are holding, but if I cut them off flush to fit in the 2x 4, I'm concerned something will loosen up. What do you recommend? Also, should the blocks be toenailed or fastened straight in from the opposite side of the truss? With screws or nails?


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## rossfingal (Mar 20, 2011)

Cut the nails that are protruding through the bottom of the roof with a
Saw-Z-All (Metal-blade) or a "Multi-Tool" - the ones that are in the way
of any blocking.
Toe-nail or screw the blocking in -
Install the blocking "every-other", rafter-bay -
Than, go back and fill in the remaining "bays".

rossfingal


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## roof52 (Apr 8, 2012)

I want to thank you all for your great assistance with all my roofing questions. 

I'm pretty much set on the blocking issue, there's just one last think I'm not sure on regarding fastening the blocks to the trusses. Is there any advantage to using screws instead of nails? If screws are used should pre-drill holes first? I do not want any wood splitting on the trusses. And is there any need to nail into the blocks from the shingle side of the roof. 

regards roof52


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## Gary in WA (Mar 11, 2009)

Screw or nail, they only give support to the joints. If in a high wind area, I wouldn't "cut the nails" as the shingle above could pull away because now the fasteners are not even to minimum code. I'd get after the installer....

gary


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