*
Hey ya’ll, I need advice! Which is better for roof decking and wall sheating? Our local home center has 1/2 cdx for $.69 more per sheet than 7/16 OSB, and I’m not sure which would be the better value. This material is for my own house, so I’m looking the long term value. Thanks for any help.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Fine Homebuilding's editorial director has some fun news to share.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
*
Ed,
On my house, I used 7/16 OSB as wall sheathing and I got 5/8 OSB from a local lumber yard for the roof. (Some older info I had on house and roof design said to use 5/8). The carpenters (poor guys) thought the 5/8 was a pain to carry up to the roof, but that it makes quite nice, solid roof deck. The roofers loved it due to it having less spring when struck.
In my observations, here in the SE USA, plywood tends to warp, and sometimes delaminate when wet. We went with all OSB because 1) it remains stable when wet, 2) at the time we built, it cost less, and 3) because all the engineering data I could find said that it would perform well in the applications for which we used it.
Also, don't fall into the trap of thinking that your large home center can provide you with the best price. Our local lumber yards are often able to meet or beat the home centers on price, they provide much more personalized service, and they deliver!
*Not much personal experience yet, but my framer likes 1/2" CDX (4 ply) under siding because he says the OSB doesn't hold nails as well. Have heard the same comment from several on this board.Suggest you do a "Search" with OSB as your key word -- you'll find lots of info already posted on this.
*If your framer was counting on nails in 1/2" sheathing to hold the siding on, you may have a problem.JonC
*Ed,Plywood all the way. It's been proven over the years, in my eyes. I've replaced a lot of OSB over the years that was subject to water damage and have seen that it rots a lot sooner than plywood. I would recomend fir instead of pine for another couple dollars a sheet, but if pine is what you can afford, 69 cents per sheet over OSB is a bargain. Red dog
*I prefer OSB for both. It lays flat and doesn't delaminate. I was slow to change, wall sheathing first and then switched for roof sheathing. I had a couple of jobs where I had to tear off delaminated sheets on roofs even though it never saw rain. It's bad enough sheathing steep roofs the first time. Also if one man is on the roof he can handle the OSB alone. Getting a sheet of banana plywood down and engaging all the plyclips is murder for one man. P.S. Never depend on sheathing to hold siding nails be it vinyl or otherwise. Nail it every 16" into a stud.
*Ed, I'll jump into the fray. I have been here before. I would say plywood. Just remember all plywood is not created equal. Many places sell seconds or blows at reduced costs which may result in delaminations, warpage etc. A good 1/2inch or today's 7/16 should have 4-ply and few or no voids. You can check the edges of a few sheets to qualify it. 5/8 should be standard for roofs up to 24inch centers. I realize code alows 1/2inch with clips in many places but you end up with a springy roof. Plywood does hold nails better than OSB, but for siding I always lay out my clapboards or beveled siding to hit studs and blocking at cornerboards and window casing. My experience with OSB is it swells with moisture, it crumbles apart with steady exposure to rain or snow, the glues/sawdust mix is hell on my lungs and tools. Any material will suffer from prolong exposure to the elements, but I have found plywood is the better product. Now should I go into my speill on the environmental degradation that is inherent in OSB and their ilk. Check out the archieves for environmentally sound building 6 March 2000 I wrote. I'll step down off my soap box now. walk good david
*Here is my 2% of a dollar on the subject. OSB gets my vote. Given equal exposure to moisture I have had more problems with plywood. I have never attempted to measure nail retention forces with anything that might be construed as accurate, but my calibrated arm hasn't yet detected any difference. Some comments suggest that the product being used was not OSB, but waferboard or even particle board. The latter (particle board) when exposed to moisture, loses any semblance of structural strength and essentially reverts to its basic component, sawdust. Waferboard is a step up from particle board but usually was made with interior rated glues, and while it withstands exposure to moisture considerably better than particle board, it still is not in the same class as OSB and exterior plywood. Waferboard can be identified by the very large wood chips, (flakes 1-2 inches on a side) present on the surface. Neither waferboard or particle board should be use a structural element. Obviously your mileage will vary.
*In my experience OSB is alright for wall sheathing-structurally eqivalent to plywood,just make sure to flash the exposed ends,moisture causes catastrophic failure quite quickly(w/in 5-8 yrs). For roof decking,I would recommend plywood as it is more torsionally rigid than OSB-especially under heavy,prolonged snow loads. This is opinion based on experience only-just remember the axiom when comparing prices-"You get what you pay for...". Best of luck.
*
View Image © 1999-2000"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Hello Gordon,Here's a little more accurate info on Wafer Board and its intended uses. Just FYI - "Here is some info for determining the grade quality, and the use of Wafer Board. I learned this through the Wafer Board Association, and the Council of American Building Officials (CABO). First of all, Wafer Board is the actual name of these panels. They areclassified into two groups: 1) Random Wafer Board, graded as R-1, and 2) Oriented Strand Board, graded as either O-1, or O-2. These panels are commonly, although erroneously, referred to as simply OSB (Oriented Strand Board). Indeed, there are two types and grades. Now here's the difference, and where they are supposed to be used. Wafer Board is simply chips of wood (usually Aspen) that are sliced off of a log. They are sliced in the direction of the grain, so as to provide the tree material strength. The chips are driedand sorted according to size. Once separated, the chips are mixed with specially formulated waterproof phenolic resins. They are then assembled into mats, and subjected to 400 degrees of heat, and 650 pounds per square inch of pressure. Wafer Board may have three, four, or five layers (depending on thickness of the panels, and complexity of the forming process). Where the distinction comes in is when the chips are placed for processing. Random Wafer Board chips are randomly placed on both inner and outer layers. The chips basically look like they go every which way (north, south, east, and west) These chips are long andthin, and when talking about which way they go, I am referring to long ways. Random is just that. The strands are just randomly placed. These panels are used for general purpose, and have the least amount of strength or fastener holding power. Attic decking, dog houses, filler pieces, etc... are the most common uses of the Random Wafer Board panels. Oriented Strand Board (OSB) has two gradings. O-1 is the best, and the strongest. With O-1, the strands are placed facing the length of the panel. This provides the greateststrength and fastener holding power. O-2 has the exterior (or face) strands facing the length of the panel, but the interior layers are random. This is still better than Random Wafer Board, but not quite as strong as O-1. Both O-1 and O-2 are recommended for subflooring, sheathing exterior or interior walls, and for roof decking."Most people have no idea that there are two very different types of Wafer Board in use, and some use the wrong one on their project.I live in a very humid, very hot climate, and Wafer Board (OSB) does not stand up to the test of time here. It does not hold a nail worth a darn (most nails are over driven with a powerful nailgun). Plywood, if good quality is used, will last a lifetime here, provided there are no major leaks for a long period of time. Just my two cents worth...James DuHamel
*I had a guy ask me once:"Why do they call it i orientalstrand board anyway ?"
*Ed,I too like plywood better.What Joe Matus says about OSB being stable when wet seems like B.S. to me. Roofs that leaked and were sheathed in OSB tended to disintergrate. OSB has a waxed side and an unwaxed side. on walls the waxed side is exposed to the exterior, but on roofs, the waxed side is usually installed inward to avoid having roofers falling off.Since the unwaxed side is exposed to moisture, it holds the water from leaks like a sponge. Plywood will also fail if left exposed to water for a long time, but OSB fails a lot faster in my opion.Use the plywood. it is more stiffer and I believe it holds nails better too. So what if it bows. Your'e gonna be nailing it down anyhow. It will straighten back out. Don't use anything less than 5/8 sheathing for your roof. If your roofers can't manhandle 5/8 ply, then they're not roofers at all! They better go find another line of work.Also, make sure that what you are buying is rated for exterior use (exterior glue) and not for interior use. There is a difference you know.Davo
*
Hey ya'll, I need advice! Which is better for roof decking and wall sheating? Our local home center has 1/2 cdx for $.69 more per sheet than 7/16 OSB, and I'm not sure which would be the better value. This material is for my own house, so I'm looking the long term value. Thanks for any help.