OSB Use
OSB Use
(OP)
With the current state of affairs/pricing with plywood, I would appreciate any personal experiences using OSB as a substitute for commercial projects.
The only side effect that I have read about is that OSB has a sudden failure mode at the limit. I thought that might be less of a concern with a bit of overdesign.
One client claims that it is more stable with respect to delaminating and warpage than plywood, but that is just one opinion.
Any and all opinions will be appreciated.
The only side effect that I have read about is that OSB has a sudden failure mode at the limit. I thought that might be less of a concern with a bit of overdesign.
One client claims that it is more stable with respect to delaminating and warpage than plywood, but that is just one opinion.
Any and all opinions will be appreciated.






RE: OSB Use
RE: OSB Use
As an engineer, it makes no difference to me whether OSB or plywood is used, as long as the material used is APA-rated properly.
RE: OSB Use
RE: OSB Use
Our policy is NO OSB ALLOWED, no exceptions. My boss calls it "wood sponge board". But we don't do new design, remediation only, primarily in the SF Bay area. We also do failure analysis and litigation work. We have plenty of anecdotal evidence that OSB does not stand up as well to high humidity and exposure to moisture. It also seems to be a bit better at providing a growing medium and food source for mold. And the truth is, it is a rare project that building materials are handled exactly as the manufacturer states in their literature, which is usually substantially different from what the sales rep will tell you.
As far as cost, it's variable, but plywood generally runs about $3 more per sheet than OSB.
I'd love to know if there is reliable 3rd party test data comparing plywood and OSB under less than ideal conditions. So far I've not run across it.
RE: OSB Use
Your boss is confusing OSB with particle board. OSB isn't all that bad. As far as mold goes, I found it amusing that it is an issue. After all, every wood stud, joist, beam, and truss is mold food.
RE: OSB Use
Nope, the boss may be over-reacting (he has a tendancy to do that), but he's not confused about the material.
Like I said, I have plenty of anecdotal evidence that does not cast OSB in a particularly good light. For our particular projects and clientele, three bucks a sheet is no big deal. But I would not go so far as to tell any of our contractors to voluntarily substitute plywood for OSB on a competatively bid project.
RE: OSB Use
OSB will swell at its edges even with small amounts of moisture increase. This happens primarily on roof sheathing. The edges swell, the board increases in length and volume, and "picture framing" results. You see waviness in shingle roofs from its dimensional instability.
If you subject OSB to the same testing done for plywood for durability (boil specimens in water), you get a significantly different result (OSB will sometimes fall apart..not always, but not predictable either).
The concept of OSB is great....the process used to keep it competitive with plywood makes it less durable and less predictable.
I have never heard of a class action suit involving plywood. There are numerous class action suits involving OSB and OSB-like materials.
I won't specify it, even though it achieves APA span ratings and the like.
RE: OSB Use
If your drawings specify APA-rated shtg, you are legally not at fault. Lawyers retain unethical "expert" engineers, same as ambulance-chasing lawyers retain unethical "medical expert" doctors. They invent reasons for malfeasance, and OSB is just a handy victim. The judge doesn't know any better. Plywood has a nasty habit of delaminating when rained on before the roofing, and I have heard builders say that's why they prefer OSB for roofs, and plywood for heavily nailed shearwalls.
RE: OSB Use
Given leaking and saturation, both will deteriorate and in different modes. In general, they are not rated for continuous wet service, only intermittent exposure.
I have tested both OSB and plywood. While each has some specific advantages, in my opinion, plywood is the overall better choice.
RE: OSB Use
Comparative product data on Plywood and OSB can be found at CanPly's website. There are engineering values for both plywood and osb on axial compression, planar shear, bending and tension and thickness swell.
JB
RE: OSB Use
Here it the link to comparative data on plwood and osb:
http://w
JB
RE: OSB Use
RE: OSB Use
RE: OSB Use
Seeing as how a client may be a builder of large, repetitive apartment complexes, that are built in many different locations, I think it is "none of my business" to allow ONLY plywood. It is the builder's choice, as long as it is APA-rated. You might notice that manufacturers of OSB tout their product as being superior (grain of salt).
RE: OSB Use
RE: OSB Use
RE: OSB Use
JB
RE: OSB Use
RE: OSB Use
Although the trend of the I-Joist manufacturer today is to provide OSB webs, Trus Joist still have series of joists using Structural 1 Plywood webs. In fact, traditionally, the webs were made with plywood and flanges using sawn lumber. The industry has evolved over the years and now they have various combinations of OSB/plywood webs with LVL flanges.
RE: OSB Use
With that in mine, if there is any question on a prodect's performance or durability, then it is not specified. Some say to merely specify "sheathing" and let the Contractor choose. In my opinion the designer is still liable because he did not prohibit the use of that specific material.
An example comes to mind; twenty years or so ago an Architect wanted to use "fire treated" lumber in prefabricated roof trusses. The industry was unaware of any issues at the time, so the building in mind, as well as several others, was built that way. About 5 or 6 years later the industry accepted and announced the fact that it was wrong to use that material because it was corrosive to the truss connector plates under certain conditions. The Architect, builder, lumber supplier and truss manufacturer all ended up in court. In hindsight, what was deemed alright due to lack of prior knowledge ended up causing many people bad times.
It seems that the OSB negatives outweigh the positives for me just by virtue that negatives exist.
RE: OSB Use
http://ww
RE: OSB Use
In the areas I've worked, OSB is both allowed and more commonly used, primarily due to cost. However, as one who walks on a roof occasionally, there's no doubt that the OSB has less strength than plywood of equal thickness.
I know "H" clips are required when OSB is used, but I'm not sure if "H" clips are required when plywood is used.
The difference, though, comes in when repairing or replacing roofing shingles. The common methods of removing old and/or damaged shingles is "shingle spades". These severely bend existing "H" clips, and no amount of hammering will completely straighten them out. When the roofing felt is laid and nailed (very specific requirements have been recently implemented in Florida, BTW, as a result of last summer's storms), a hole is created everytime you step on the felt over a "H" clip.
This seems like a case of very inconsistent, perhaps not well thought out code requirements. If plywood was required, and/or perhaps closer joist spacing, then "H" clips wouldn't be required, and you'd have a tighter product if/when the roofing is replaced.
RE: OSB Use
H-clips are required for panel edge supp)orts (OSB or Plywood).
In Canada, H-Clips should be spaced:
One at midpoint for supports upt to 600 mm
Two at 1/3 points for suports 601 to 1000 mm on centre
Three at 1/4 points for supprts more than 1000 mm on centre
I've heard about a Plywood T&G (Tongue and Groove) Profile for Roofs called EASY T&G that supposedly eliminates the need for H-Clips.
Does anybody have any experience with this product?
RE: OSB Use
RE: OSB Use
Another question I would have is - who was the local inspector who failed to do his job?
RE: OSB Use
What is the code body you are working in?
RE: OSB Use
If you have ever watched a group of contractors with nail guns, you will see they get the gun bouncing off the deck. This means that the gun is not calibrated correctly. It also means that the fastener is puncturing the top ply and reducing the effective shear value of the panel by 70% (+/-).
This does not happen with OSB. In addition, reports of failed fastener pullout in OSB were actually the result of stable fasteners awith only (1) leg engaged. OSB actually has a better pull out strength that plywood.