Inspected a house about 30 yrs old and found that no h clips had been installed. Is this a concern?
Gary,
there are too many variables to be able to answer that question, such as thickness, OC between rafters, thickness of sheathing, and whether or not is was marked “for spacing”
Regards
Gerry
Gerry, what then do u recommed for wording? When inspecting the roof are we looking 4 things like thickness, OC, etc?
Gary,
you need to look for the manufactures imprint on the sheets to see what the specification is.
I would recommend that you take this course from APA it’s free
register and take unit 3
Regards
Gerry
In addition to getting a little more background information, look for visible signs of defects at the sheathing edges around mid span between the rafters, such as buckling or bowing. H-clips become more important with thinner panels and OSB type sheathing, possibly combined with larger rafter spacing (such as the usual 2’-0" roof truss spacing).
Also, if you are in an area that does not have significant snow, wind, or earthquake loading it is more likely that thinner roof sheathing is used where H-clips become more important to help support minimum roof live loads from people on the roof (e.g. roofing construction).
JMO & 2-nickels … 
I don’t think H-clips have been around for thirty years, probably within the last 20 years at least. But then again…
H- clips were not being used 30 years ago in Hawaii (and I would imagine the rest of the nation.) We started using them around 22 years ago after Huricane Iwa. This changed alot of requirements with regards to home building.
I would check with your AHJ to see when they became a requirement in your area.
In my humble opinion H clips are used because the framers and builders are too cheep to use proper tounge and groove sheeting on the roof and could get away with inferior crap.
Larry
Larry,
Tell us how you REALLY feel 
tg
I am getting a little frustrated with this H-clip scene, because 30 years plus ago, a sheet of plywood used to lay flat on the roof or the floor.
Doesn’t that raise a red flag? Today, you could make skies with the 5/8" plywood. No wonder that someone invented the h-clip. It would not surprise me that it was the manufacturer himself. Ironically, I was unable to find the background on the h-clip, hmmmm.
Didn’t this problem start when Contractors started to save a few bucks and intall 1/2" plywood on the roofs instead of 5/8"?
It is amazing how some people will go to the extremity of actually designing something or product to compensate for the lack of ethical Manufacturing Products the way they were.
Saving labour and Money is what it is all about.
Marcel 
</IMG>
I build my first house in the mid 70’s and used H-Clips with roof sheathing panels as per CMHC Wood Framed House Construction recommendations; many factors came into play as Gerry mentioned including geographic area (snow loads)…
H-Clips in addition to re-enforce roof sheathing also provides spacing for expansion. Panels expand as wood normally does when moisture content increases.
As someone said: Saving labour and Money is what it is all about…
So what is the rule on spacing for the H-clips? I normally have seen them about every 2’ but wonder if a 6’ space between two is ok? The rest of the attic had a clip between each of the 2 rafters but one area had quite a gap. Do you call it out and how would they fix it other than pulling the shingles and felt off? I’m not sure this pic is going to be too clear.
They are usually installed between trusses. If they were omitted, I recommend installing 2X4’s between trusses for proper sheathing support.
They are suppose to be every two foot…often what happens is they fall out during installation. I don’t know how many of you have stood on a two story 10/12 pitch roof with a 4x8 sheet of 1/2 plywood blowing in the wind all the while trying to get the plywood to fit into the clips without them falling down to the to the ground while keeping your balance…it can be a challenge. I definitely don’t want to have to be lifting a 3/4 inch plywood or osb over my head while standing on a roof…plus its just not needed…its overkill. I thought we were suppose to be building smarter and better…isn’t that what Green is all about…but I digress…plywood clips have been around at least since the 70’s.
While some older building practices are fine…many are not as is evident by the problems we see in older homes. I will take 3/4 Advantech over the 1/2 plywood & 5/8 particle board any day…as well as the 3/4 diagonal 1x6 with 1/2 ply over same. Many of the materials used today are far superior to what was used back then.
Marcel is correct in that when 7/16 osb is installed on rafters or trusses at 24" o.c. their would be clips or blocks under same.
It’s an engineer’s or architect’s call whether to install them. If you don’t see them it’s not a defect unless you know for a fact that they were required in the jurisdiction in which the home is located at the time the home was built. Many, many homes have been built without them. I would never call lack of them a defect without documentation showing that they were required.
Their purpose is to help support panel edges, not act as spacers, since sheathing is butted tight to them. When they’re used, it’s usually one per rafter bay.
When I started building in the early 70s, we were using h clips. Don’t know when they first started being used but it was definitely (at least in my area) more than thirty years ago. Kenton is right except for in areas where they are required (like where I live).
Copied from: http://www.tecotested.com/techtips/pdf/tt_edgeclips
H-clips provide the recommended spacing between two adjoining panel edges,
allowing room for panel expansion if the panels get wet during construction…
1/2" plywood on the roof, you must be kidding…how about 3/8"!
Plywood in adjacent courses butt tight to the H-clips and I’ve seen it buckle at the clips after getting soaked by rain. That means each panel buckles in 4 places along it’s length. If it buckles enough to show- and it can… it’s a defective installation.