There will always be options available when doing any construction project. This includes the material used for the roofing deck. Can you use OSB?
OSB is a suitable material that offers many of the same benefits as plywood for roofing. It is less expensive and provides strength, even in high wind and seismic activity areas.
There will be differences in opinion regarding using OSB as a roofing material. For many years before OSB became popular, plywood was the go-to material.
My company uses a combination of plywood and OSB, depending on the roof we install. OSB, when installed properly, is perfectly acceptable, but some of our clients still want to see plywood because it looks better to them.
Considering the differences between plywood and OSB can help you to see why it is a suitable building material. In addition, OSB has come a long way since its early days, and it is now manufactured to very high standards.
The primary reason why many builders, myself included, choose OSB is that it is cost-effective. You must stay competitive in today’s market, and saving money on roofing material is one way to win the bid.
Another benefit of OSB is that it can be purchased in a 9-foot sheet. Plywood is typically sold in either 8-foot or 10-foot sheets, which limits you to a certain extent.
The density of OSB is also something to consider. The strand layers that are compressed in OSB can be very thick, so there will not be any weak spots. The same can’t be said for knot holes in lower-quality plywood.
The big difference between OSB and plywood, discussed in the next section, is the material’s ability to handle water. There’s nothing wrong with allowing OSB to get wet, but you do need to give it time to dry out, or you could have problems.
We will discuss some of the positive reasons why you should use OSB in your roofing business and why you may want to use plywood at times. It comes down to the homeowner’s perception and how they view the use of OSB. After all, we want to win those bids.
The bottom line is APA – The Engineered Wood Association approves using OSB and says it is on par with plywood. There will always be advantages and disadvantages with either type of material, but there is nothing wrong with using OSB for roofing.
Should You Use OSB For Roofing?
As we established, the use of OSB for roofing is perfectly acceptable. You can use it in all situations, providing the same structurally sound benefits as plywood.
That doesn’t mean there aren’t some problems that need to be considered. These issues can be overcome if you know about them in advance.
Weight
One of the problems that are not often considered is the weight of OSB compared to plywood. OSB is heavier than plywood, so you must have more manpower on the job site when hauling it around.
The weight should also be considered when putting it on a roof. This is more of an engineering than a construction concern, but you don’t want to have so much weight on the roof deck that you are causing the roof to become structurally unsound.
Saturation
There is a notable difference in how quickly plywood gets saturated. It might surprise you that plywood soaks up water faster than OSB, but that isn’t the only part of the story.
If OSB is allowed to be out in the weather and it is raining for a few days or a week, it could become completely saturated. This is a problem because OSB takes longer than plywood to dry out.
If you have a problem with OSB getting wet, you must let it dry completely before covering it with felt or any other roofing material. Otherwise, the OSB could deteriorate over time and lead to other issues.
Swelling
When plywood gets wet, it swells. The same is also true of OSB. The difference is plywood will swell evenly across the entire board, but OSB tends to swell more on the edges.
The edge swelling wouldn’t be a problem if OSB returned to its normal shape and size after drying out. That doesn’t happen. When OSB swells on the edges, it will maintain that shape permanently.
Roof Leaks
Although we don’t necessarily want to consider the possibility that a roof will leak, it will happen sometimes. When OSB is subject to excessive humidity and roof leaks, the panels can end up degrading quickly.
The same would also happen with plywood, but since plywood dries out more quickly and doesn’t swell on the edges like OSB, it is not as big of a problem. This issue will be minimized if the roof is constructed correctly and maintained.
Cutting Holes with a Hammer
Many contractors take the short route and punch holes through the board with a hammer. Doing so may be convenient, but you are weakening the deck when doing so.
It has to do with the way OSB is constructed. As you hammer away on the board to punch a hole through it for wiring or plumbing, you weaken the oriented strand bonds.
It will be necessary to cut holes in the roof deck for most jobs, but you should do so using the proper tool, such as a hole saw or reciprocating saw.
Copyright protected content owner: ReadyToDIY.com and was initially posted on March 22, 2023.
What Preparations Do You Need To Use OSB For Roofing?
There are not many things to consider when preparing for an OSB roof deck. The process is very similar to using plywood, with a few exceptions.
1. Allow for Expansion
As we mentioned several times, OSB tends to expand when wet. That is why you must leave a gap of 1/8 inch between the roof panels and the wall or from one board to another. If you don’t, the deck could buckle if it gets wet and swells.
2. Nail at the Proper Location
You should prepare for this in advance. Maintain a 1/2 inch space between the edge of the OSB and any nails. Otherwise, you risk splitting the board.
3. Allow the OSB to Dry
There will be times when the OSB gets wet. Perhaps you have a delay in construction, or the OSB may be out in the weather unexpectedly.
It’s not the end of the world if OSB gets wet, but it is a problem if you cover it with roofing material before it dries. Always ensure that the panels are dry before adding any roofing material. Keep in mind that OSB dries slower than plywood.
Copyright article owner is ReadyToDiy.com for this article. This post was first published on March 22, 2023.
How To Use OSB For Roofing
Now that you have prepared to use OSB for roofing, it’s time to get started. Here are some steps to take.
Pro Tip: Always install OSB with the grade stamp down so it is visible from inside the attic. If the inspector can’t see the grade stamp because of the roofing material, they won’t be able to approve the project.
1. Choose the Proper Layout
The APA recommends not having a panel smaller than 4 feet. You may have to block unsupported edges near ridges or gables.
As you install the sheathing, ensure a 1/8-inch gap is maintained between the edges of the panels, including at the walls. If the OSB does get wet, the lack of a gap could lead to buckling.
2. Choose the Proper Fasteners
When using OSB as a sheathing panel, you should never use a nail smaller than an 8d nail. Another issue that you may run into with OSB is head pull-through, so always use a full-headed fastener.
You must use a ring or screw-type shank nail when you work near a Gable or Ridge. These will have the extra staying power necessary in those areas.
There are also going to be specific guidelines for selecting fasteners and using them in areas where high wind speeds are possible. Always check with the local AHA for more information.
3. Spacing the Fasteners
Your fasteners should be spaced properly on each OSB panel. The last thing you want is for a panel to blow off in a storm, which could cause the entire structure to fail.
The fastener spacing will be a part of the inspection, and most inspectors are very picky regarding this detail. It’s easier to get it right the first time rather than going back and fixing things later.
4. Remember the Ridge Vents
Ridge vents help to pull air across the roof and to bring out the moist, hot air from the attic area. With OSB, it is best to have vent holes rather than continuous vents. This is especially true in areas of seismic activity or high winds.
OSB is an excellent choice for roofing decks. As long as it is kept dry and installed correctly, it is just as suitable as plywood but comes at a reduced cost.
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ReadyToDIY is the owner of this article. This post was published on March 22, 2023.