I understand the reasons for using the H-clips with plywood roof decking … edge alignment and sheet spacing. But what happens when the plywod expands? Does the clip crush the small area of the plywwod and allow expansion?
“When asked if you can do something, tell’em “Why certainly I can”, then get busy and find a way to do it.” T. Roosevelt
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are you 'simple but elegeant'?
The clips provide a gap of about a little more than 1/8" so that in the event it does swell it will swell into the gap and not cause a buckle. Is that what you are asking? I have used them before and haven't yet seen any swelling. If they were to swell I imagine the little dimple on the H clip that causes the gap would be buried into the wood. Specs call for two clips per edge. Not enough to be significant. That dimple is smaller than a pencil eraser.
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
I've never heard of h-clips used for spacing sheathing before. I thought the only reason for h-clips was for 24" centers.That's where I've used them when I did roof trusses and one job that I stick framed @ 24" center. I've never once spaced my roof or deck sheathing anyway.
I space the top of the horizontal wall sheathing with a nail but not the butt joints. I've read about this and mentioned this before. I've never had a problem not spacing my roof sheathing or butt joints on wall sheathing.
Reason I ask, I'm having a new roof built on a new building, with trusses at 24" and they are using h-clips on all edges of the ply: top & bottom, left & right. Just wondering if the clips would interfee with expansion.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
The clips won't hurt expansion since it won't be happening with plywood. I'd wonder why they used clips on the ends of the sheets, hopefully the ends landed on a truss. OSB sheathing can expand but plywood won't be a problem unless there are some very bad conditions. Even then, it's more likely to swell in thickness than overall dimensions.Beat it to fit / Paint it to match
I've never used the clips for spacing....what a waste of money. We always use our speed squares.....just stick it in on each end of the sheet and you have a nice little gap there and it was faster and didn't cost anything.
Sam
I can't even imagine how they manage to put clips on all 4 sides.
I always use ply-clips on top and bottom but cant imagine doing it on all 4 sides.
Seems like alot of wasted effort.
ive never seen the clips cause any problem with expansion, and i would assume that they would only help with it fore the fact that the sheets are more evenly spaced and or consistantly spaced.
>> they are using h-clips on all edges of the ply: top & bottom, left & right. <<Why would they use h-clips on the sides???As far as worrying about expansion, I wouldn't. If that was the case no one would use clips. I don't even space sheathing and I don't have any problems. You can do what you want but clips on the sides makes no sense to me at all, and that's another thing I've never heard of before.Joe Carola
Now that I think about it ... I was watching from the floor as they laid the ply and I saw them put the clips top & bottom, but didn't pay enough attention to the sides. And it would be a trick, wouldn't it.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
What I want to know, if if spacing is so important, why don't hey make sheets that are 95 3/8" x 47 7/8" or similar?
>> What I want to know, if if spacing is so important, why don't hey make sheets that are 95 3/8" x 47 7/8" or similar? <<Matt,I never knew that spacing was so important on roof sheathing and decking before until these forums. Like I said, I've never spaced either. I never spaced wall sheathing until 5-6 years ago when inspectors started saying something.Joe Carola
Actually... I've never heard of spacing wall sheathing. :-)
Our inspectors make us space wall sheathing 1" and drill a 2" hole in any stud space, like below windows, that can't breath.
85005.17 in reply to 85005.15
>>Our inspectors make us space wall sheathing 1" and drill a 2" hole in any stud space, like below windows, that can't breath. <<
One inch: Wow!!! The spacing we do on floor sheathing, for example, is more like 1/8th. Does that mean you have to cut 1" off of 2 edges of every sheet? With a one inch space, does that mean that a stud has to be doubled everyplace a plywood seem is to occur. Am I misunderstanding something here? Maybe the 1" was a typo?
And the 2" hole? What's that about? wouldn't every stud space come under the category of can't breath so do you need a 2" hole in every stud space???
Would you mind expanding on those items? You must live in an area that has special conditions and therefore require special treatment? What area do you live in? Not questioning you - just trying to learn something here....
The 1" is just for horizontal spacing. It leaves a gap at the 4'-0" level of your wall to let water vapour migrate to the outside. As our stud walls are typically 8'-1" it works out quite well. Some framers prefer to have one of their crew drill 2" holes top and bottom in every stud space. Either way it can be a problem if you are siding with a nail gun and don't recognize you have missed the sheathing.
All this and now compulsory rain screens on all new construction including houses in British Columbia, because of rot problems in condos that caused several billion in claims. Rot that was for the most part due to inappropriate design and shoddy construction by large builders. Now we all pay.
All I can say is WOW!
And now that I'm over the initial shock...
So, I guess there are special requirements for the house wrap/felt/etc like maybe a specific perm rating, and you said rain screen - did you mean that literally as 1x3s or similar tacked all over the outside of the house before the siding is applied? Special flashing requirements? I assume there is a sheathing/weatherization inspection before the siding goes on and the insulation goes in??
And, what about interior vapor barrier - I guess polyethylene is out? (actually we don't use that here any more) What about insulation - is a specific kind required? I'm very intrigued... Who knows maybe this is a glimpse of the future... - or maybe not :-)
To become registered as a builder here, which you have to do to build for anyone but yourself, you have to be registered with one of the companies offering home warranty protection. The government has so far left it up to them to determine the acceptable details - which potentially could vary from company to company. But in general it includes the 1"x3"s, a choice of wraps or felt, gaps in the sheathing, batt insulation and a 6 mil. poly barrier.
The requirement to include rainscreen, with all its attendant details, has been in place for several years for multi-unit buildings. It has spawned a new profession here of Building Envelop Specialists and most medium to large projects employ them.
My beef is with them extending the requirements to include single family dwellings, when there is no evidence that there has been a problem with this building type. No spike in insurance claims - really nothing to support it. To my mind, it will cause more problems than it will solve. The detailing at the top and bottom of the walls and around windows are not straight forward. I have always designed houses with large overhangs to allow the roof to do most of the work and it is hard to understand why a well detailed and executed conventional wall isn't sufficient.
Edited 2/6/2007 8:52 pm ET by fingersandtoes
>> To become registered as a builder here, which you have to do to build for anyone but yourself, you have to be registered with one of the companies offering home warranty protection. << Here, in NC, USA, builders are required to give a 1 year comprehensive warranty, and a 10 year structural warranty. None of this being registered stuff though. The way most builders do it, including the one I work for is we take care of the 1 yr portion, and I do almost anything to make our home buyers happy. Regarding the 10 yr structural warranty, we purchase a policy (if that is what it is called) for the extended warranty from a warranty company, and that is the end of our involvement. To tell you the truth though, as cheap as these warranties are - maybe $500 - I can't imagine they are that good, and I'm sure the policies are riddled with fine print.
>>The government has so far left it up to them to determine the acceptable details - which potentially could vary from company to company. << In a way it makes sense for people who are involved with investigating building failures to set rules, but still, I'm not sure that an insurance co is the best entity to do it. I think we all know that insurance companies tend to be very self serving. You know - the old "you have to conform to a bunch more rules we have, and by the way, we are raising your rates because of 9/11 or some storm that was 1000 miles away... :-) >>But in general it includes the 1"x3"s, a choice of wraps or felt, gaps in the sheathing, batt insulation and a 6 mil. poly barrier.<< 1x3s I think is a good concept, I'm not sure that it is really necessary though. Lapsiding and even vinyl siding provides some ventilation, so I'm not really sure they aren't just adding un-necessary expense to the cost of homes. That alone, I'd put close to $1000 for a moderate sized house. Regarding the 6 mil poly - we used to do that on our walls. The practice has mostly been abandoned in my area, I guess due to mold concerns. I personally quit doing it under advisement of some energy consultants when I was building some Energy Star homes. We have never put vapor barriers in our ceilings other than maybe craft faced batt insulation, which I don't think hardly counts as a vapor barrier. It is what I have installed in my walls too - I know... not the best, but I think it is passable for our climate.
>> The requirement to include rainscreen, with all its attendant details, has been in place for several years for multi-unit buildings. It has spawned a new profession here of Building Envelop Specialists and most medium to large projects employ them. << That's pretty interesting. Is there some kind of certification or something? My siding guy does that, and they are pretty good, but other siding guys I had were not so great, especially if the framers (before them) didn't do a good job at lapping the paper, etc. I wouldn't mind going to a class about that. I think I have all the basics down pretty good, but would like to learn some more about the details.
>> My beef is with them extending the requirements to include single family dwellings, when there is no evidence that there has been a problem with this building type. No spike in insurance claims - really nothing to support it. To my mind, it will cause more problems than it will solve. << Like I said, typical insurance co stuff...
>> The detailing at the top and bottom of the walls and around windows are not straight forward. I have always designed houses with large overhangs to allow the roof to do most of the work and it is hard to understand why a well detailed and executed conventional wall isn't sufficient. << I'm a big fan of overhangs... although the moderately priced houses I build only get 12" overhangs. I can only build what people are willing to pay for, and believe it or not, even the 12" overhangs could be questioned. I just can't understand why so many home buyers just want cheap square footage - the only thing I can say is that they are just ignorant to good building practices. I'm OK with the 12" overhangs considering all the national builders and most of the large regional builders do not put overhangs on their side or back gable ends on cheap to moderate priced houses... BARF!!!
This whole situation of yours is very interesting though. BTW - one probably stupid question - these 1" gaps and 2" holes... obviously they are well covered by the rainscreen building paper so there is no bulk air infiltration - right? Also, if you leave a 1" horizontal gap, doesn't that effect the shear strength of a wall assembly pretty severely? Our code requires shear panels only 4' of each side of a corner and then every 25', which I think is pretty standard, but maybe that is where the 2" holes would come in as an alternate to the 1" air gap?
It seems like for your area's situation they would identify a "breathable sheathing" with a high perm rating that also had structural characteristics... This whole thing makes me wonder (even more) about using foam board for sheathing, which generally is not breathable, and further, I wonder the same about foam insulation. Obviously, in your case, I guess there is no reason for insulated sheathing if it is going to have large holes in it... Also, the idea breathable sheathing is contrary to insulated sheathing. Confusing...
Exterior side foamboard sheathing considerations again come into play bringing with it the whole vent/no vent, tight house, hot roof, cold roof issues and the continued controversy they employ.
It would seem fingersandtoes recent requirements for multi-unit buildings being broadened to also include single family dwellings must make whatever government enity that decided on this expansion think they have a handle on the situation.
Apparently batt insulation is still the norm there seeing the stringent 1" gap and 2" hole requirements so foamsheathing would be out of the question ie your example of breathable/insulated sheathing.
I had no idea the ventilation issue was under such attention up there.
is it Saturday yet?
This is earthquake country. In the Loma Prieta Quake of 89 , buildings in SAn Francisco had the plywood pop off. The stress and distortion of one sheet pushed on the next on down a wall and when it got too great the sheets started exploding off the building, gaps allow the building move and releve the stress.
That's pretty interesting. What sized gaps?
What I want to know, if if spacing is so important, why don't hey make sheets that are 95 3/8" x 47 7/8" or similar?
I dunno if they still do or not, but years ago, I was joisting a floor (300'x50' or so) with the sheathers following behind. Aboout halfway thru, the foreman and lead sheather came up and told me my layout was off!?!?!?
Walked back to where the sheathing was done and they were all butted tight, with the printed side up. Guess what the printing said. Yep. "Sized for spacing." The sheets were only 47 7/8" x 95 7/8".SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
Any T&G floor sheathing is undersize. Over all dimensions are 4'x 8' , but the 4' dimension is reduced by the amount the tung seats in the grove.
Learned that lesson on a bank roof where we had bolted 2x4 to the bar joist for T&G plywood. At 2' o.c. the small difference in the plywood size had it fall short of the sleepers about halfway up the roof. Oop!
Advantech calls for 1/8" spacing on the ends and 1/16 at the T&G joint. If you drive it up tight, the warranty may be void, if there are any problems down the road.
Dave
Right - but why don't they make the sheet 95 7/8" long?
BTW, another minor point: if one is working with floor trusses and some I-joists. spacing on the 8' dimension gets a lot easier because of the wider joists. Of course, that doesn't happen with roof sheathing, except maybe in the rare instance when you use I-joists for rafters.
A 1/16" spacing on the long axis means somewhere between five and eight sheets before you crowd the break point on rafters or joist. Shaving an 1/8" off every fouth sheet solves the problem for me, but I work alone most othe time and don't need to keep reminding a crew to not pull joist or rafter out of line. I can see how it can become a problem for framing crews though. a shorter sheet would present the reverse problem for those same crews. No spacing and the shorter sheets would evenually fall short.
That's why they pay us the "big buck", to think through and fix issue like this.
Dave
If they layed out on 24" and they used clips on the 4' ends by the 6th sheet they aren't hitting a truss.
I get PO'd when my sheet's get off a 1/4".
Since when does the plywood on a roof deck expand? I've never heard of or seen this take place. If the plywood is expanding then I would think there is a leak somewhere that would have to be fixed.
The only justification for using the H clips is where a roof is shallow enough to be walked on, like an 8 pitch or less. This reduces the risk of someone stepping on a seam and causing the plywood (which is usually 1/2 inch) to bow, which in turn could damage the roof.
"Since when does the plywood on a roof deck expand?"Anytime it is laid dry and then absorbs moisture from the air or from getting rained on. It is not always that super dry when laid and does not often absorb enough to make it noticeable, but it happens nonetheless. There have been threads here started by those who have ahd to go back and re-roof and run a saw kerf to relieve the pressure from this problem. There is a reason why the manufacturers of the sheet goods like plywood, /OSB and Advantec recommend spacing and why some codes and inspectors require it.Personally, I think we don't see more probelms from this phenomenon because the sheet goods are damp when applied, so they don't do more swelling after application.
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We had problems with a house where we sheathed the roof with OSB. We guessed that the edges absorbed moisture and swelled (we didn't space them--butted all our roof sheathing tight whether we used OSB or plywood). We finished the "problem" house and were working on one across the street and every morning at about 10:00 you could look across the street and the light hit the roof just right so you could see a ridge at every joint in the OSB through the shingles. (House has since burnt to the ground--not our fault! (I think it was an electrical fire))