osb and roofing

[noslin]

this could apply to osb where used in other aspects of building your home too. OSB has been used for long time. they are now coming with reports that it might not be such a good product to use. I have some literature at work that the boss picked up at the western states roofing convention this year where they pointed out issues in using the OSB. ill see if i can get it from work and post it up or put notes up about it. but i think this link here (pdf) is pretty much noting what is probably on the information he received.

in long , the wood loves to soak up the moisture and expand. one thing i didnt realize is they paint the ends so moisture doesn't migrate in the ends. how many times have you ever seen someone repaint the edges of the osb after they cut it? other issues that i have witnessed is massive mold occurring where OSB was used for substrate on a roof on the coast (california). the roof was toast within four years. it had to be reroofed and all the osb had to be replaced as it was gone and had tones of mold that just ate it up; its crazy to see and unbelievable.

so, from a business standpoint looking at potential issues we are going to stop using it on reroofs. if used, OSB HAS to stay dry, you cut the edges you need to recoat them. this article also says an 1/8" gap is need too for expansion. look at the article, just skim down past the first page or so and it gets into the meat of it. there is more information out there if you search for it. if you have it now, i would make sure you have good attic ventilation on both eave and at ridge.

http://www.google.com/url?sa=t&rct=...lOjuGWCzbGCCQGA&bvm=bv.72197243,d.cGU&cad=rja

anyways, thought i would make a thread about it as i see lot of ppl using OSB on the roof's (and rest of house).

dean

 

[Big Bad Dad]

I built my home and sheathed the roof with OSB 23 years ago. No problems.

 

[8man]

We've been using OSB roofing on the Texas Gulf Coast since 1989 with no problems. Interesting, I'll look into it though.

 

[yeldogt]

I would bet that the dryer the climate the better it is for OSB. At my beach house all the houses around me have been rebuilt over the past 30 years with OSB -- anytime they get damaged or remodeled you can see the evidence of decay. It just does not like water.

It also does not hold a nail like plywood. We had some houses built during the boom a few blocks away -- and you can see where the OSB has bowed on the roof and even on some of the walls.

 

[Falcon67]

I need to get a picture of the shed in the yard across the alley. It was built about 3 years ago and is all OSB with a slant roof. No paint or anything else, just an OSB box about 8 x 8 x 8. It's discolored but is holding up fine. Also, every OSB roof I have seen uses the H type spacers to keep the panels apart.

A house we owned in the way-back had the roof re-done with plywood after the old wood shingles were stripped. In 3 years the roof had waves all over it. So - IMHO, YMMV.

 

[readhead]

Plywood will deform also if it is soaked. OSB and plywood are not meant to be exposed to the weather forever. If you open a roof or wall and the sheathing is rotten from water it isn't the fault of the material. OSB has been proven to perform for what it is made to do. They did make one important change about 45 years ago. It used to be smooth on both sides. After enough people fell off roofs they roughed up one side.

 

[Chuck]

Sounds mostly like a ventilation problem to me, too. It's hard to keep things dry in a coastal environment. I wonder what they are doing in Texas on the coast that builders in CA aren't?

 

[ACDNate]

The big thing to take away from that report is that OSB is fine but you better make sure its all installled correctly.

Someone mentioned the spacing clips, I usually see those on roofing but never on walls. Probably would help.

 

[GTO]

http://www.huberwood.com/

 

[WVBrady]

The big thing to take away from that report is that OSB is fine but you better make sure its all installled correctly.

Someone mentioned the spacing clips, I usually see those on roofing but never on walls. Probably would help.

I used the almost 1/2" osb on my garage roof when I built it 30 years ago and haven't had any problems. We started to use the clips, but I noticed that the sheets were not all of the exact same thickness, so some of the clips did not lie flat. I thought that they would tilt and make holes in the roofing, so we quit using them. I didn't notice that there was any problem with the few that we did use.

 

[Hornman]

Back when OSB first came out, the glue they used was not sufficiently waterproof for roof decking. Combine Gulf of Mexico humidity with tthe poor glue and the OSB manufacturers got to replace MANY roofs in Florida and Texas. After that, they reformulated the glue/waterproofing for OSB and it has been pretty reliable ever since. As long as you use a name brand product you should be OK. This is one case where you get what you pay for: if you save too much money on initial purchase, you may have purchased problems down the line.

 

[jlckmj]

Back in 1975 I built my first garage in Chicago. I did not have enough money at the time to put siding on the walls. I had used 1/2 inch OSB (called aspenite (sp) at the time) as a sheeting on the wall studs. I found a gallon of stain at my parents so I wiped it on the OSB to try and protect it temporarily. We moved and never did a thing with it.

I went by to visit an old neighbor last year and walked to his fence line to take a look at the garage and it still looked good and no one has ever put siding over the OSB. It is now painted to match the house with batten strips covering the vertical seams.

So I guess if you seal it and or keep it dry it will last.

Jim

 

[noslin]

here is a few pics of a roof with osb used on it. first roof was built up, next roof was single ply, third roof was single ply with a complete tearoff, including all the sheeting on the roof. was couple hundred squares. this all happened within four years. the second guy didnt do a good job and just went over the bur roof. he should of told the owner how bad it was. i think the roof was shot within the first two years.

the problem arises in keeping the roof dry and getting it covered quick. problem is on some commercial jobs they dont roof it too fast and just one rain, the morning dew, etc can ruin the day. there is more too it, so this will give you an idea how important venting is too even though its not a house.

ill find the article from work and get it posted up.

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dean

 

[ACDNate]

Wow, I didn't think you could use OSB for flat roof applications.

 

[Falcon67]

the problem arises in keeping the roof dry and getting it covered quick. problem is on some commercial jobs they dont roof it too fast and just one rain, the morning dew, etc can ruin the day. there is more too it, so this will give you an idea how important venting is too even though its not a house.

Rains often here on new uncovered roofs. 1/2 of my shop attic floor is OSB that was laying open and held rain water during the build morw than a few days. It's been three years, the OSB is no more "fuzzy" than it got once it dried out. Those pics look like serious long term moisture issues. Also, our house is now 14 years old. We bought it in 2010. First thing I noticed was that there were plenty of soffitt vents and zero roof vents. I added 5. The decking (OSB) hasn't suffered either way. The shingles are about 5 years "older" than they should be because of the trapped heat over 10 years.

As above - article doesn't say it's bad, just says be sure it's properly installed and venting is handled based on the local climate.

 

[readhead]

OSB and plywood are interchangeable for any application. All of these horror stories have nothing to do with the material. If you have a roof leak the substrate will rot no matter what it is. Trying to make OSB evil has no purpose and shows a complete lack of understanding of building material.

 

[Average_Joe]

OSB and plywood are interchangeable for any application. All of these horror stories have nothing to do with the material. If you have a roof leak the substrate will rot no matter what it is. Trying to make OSB evil has no purpose and shows a complete lack of understanding of building material.

Quoted for truth

 

[Chuck]

... i think the roof was shot within the first two years...

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dean

That actually looks to me like a ventilation problem. Blame the architect, actually, or whoever modified the roof design against the architect's directions if that's what happened.

Specifically the second layer of OSB below the roof joists created an unventilated space. A good wall or roof design should never, ever create an air gap between layers that isn't ventilated to the interior of the building (if it's inside the insulation layer) or to the outside of the building (if it's outside the insulation, like the cavity on a brick screen wall, which is ventilated and drained).

I have to pound this into the brains of some of our architects all the time. This is supposed to be one of the critical core things they are trained to do right, and you'd be amazed how many times some of them still screw it up.

Moisture will always move through a wall or roof sheathing. If there's a part of the assembly where the moisture is allowed to linger on the cold side of the insulation, it will condense, and the inside of the cavity will stay wet. If this was an air conditioned building in the south and that cavity was sealed off too thoroughly from the air conditioned space, but under the flat roof insulation, that moisture may well all be condensation (assuming it wasn't just a leak from a poor roofing install, no amount of proper ventilation will save that).

If that looks bad, you should see how quickly steel structure rusts in the same conditions. It's awful.

OSB and plywood are interchangeable for any application. All of these horror stories have nothing to do with the material. If you have a roof leak the substrate will rot no matter what it is. Trying to make OSB evil has no purpose and shows a complete lack of understanding of building material.

Yes. Yes, yes, and yes!

 

[w33b8t1]

If you want something to last 1000 years you should build it from rock. Life is full of trade-offs.

 

[wnstwolf]

Good friends are top end house builders and swore by the use of plywood in his house construction. Actually used it as a selling point. Even those paying $750k and higher are cheap and do not want to pay for something they can’t see. He hated to go to OSB more about stubborn than anything else. In 1998 a guy from Huber wood products asked him to use a coated wood system on his homes. Reluctantly he took a stab at it. He should have bought stock.. It was his first intro into in Zip walls and Advantec products.. All of the Huber selections show extensive R&D even keeping one of the T&G products in a pond for a month.. we are living in 2014 not too many trees around to sustain plywood like the good old days. Forests maintained just for the OSB world are the norm and the glues are refined to meet today’s needs. Installing this stuff properly is an entirely different matter and anything installed wrong will fail..

 

[ACDNate]

we are living in 2014 not too many trees around to sustain plywood like the good old days.

Um? What? There is far more standing timber today that there has ever been. Were talking before Columbus landed on the shores.

 

[NUTTSGT]

here is a few pics of a roof with osb used on it. first roof was built up, next roof was single ply, third roof was single ply with a complete tearoff, including all the sheeting on the roof. was couple hundred squares. this all happened within four years. the second guy didnt do a good job and just went over the bur roof. he should of told the owner how bad it was. i think the roof was shot within the first two years.

the problem arises in keeping the roof dry and getting it covered quick. problem is on some commercial jobs they dont roof it too fast and just one rain, the morning dew, etc can ruin the day. there is more too it, so this will give you an idea how important venting is too even though its not a house.

ill find the article from work and get it posted up.

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dean

That's not an OSB issue, that's a hack install issue.

I can see where it appears where the roofing has pulled away from the srew in edging on the right side. In the background, you can see where they applied the roofing right over the shingles. It doesn't matter what type of roofing materials you use, the lower layer/course is never applied over/on top of the upper layer/course.