What’s the difference in OSB vs. plywood? They are certainly two very similar items that are used in almost identical applications. The general public often calls plywood OSB and OSB plywood. So, what’s the difference, really? Is it like the difference between Coke and Pepsi or is it more serious than that?
While they can be used for the same purposes, there are significant differences between the two and I’ll show you what I’m talking about below. I’m not going to go into the almost infinite varieties of thickness since thickness is not a real concern here. Mostly what I want to focus on is the differences in construction and performance so that you’ll know when to use one over the other.
Since sheathing (what plywood or OSB are called when used on the exterior of a house) is rarely, if ever, seen again once you cover it up with siding or shingles, it’s important to choose the right materials for the job. Failure of the sheathing is extremely expensive since the everything attached to it needs to go as well. You want to make the right choice the first time.
What is OSB?
OSB is short for Oriented Strand Board. Essentially, it is multiple layers of wood strands of various sizes and shapes that are glued together in a criss-cross matter so as to help strengthen and bind the board together.
Since it is made of small pieces of wood rather than larger sheets like plywood or even more so like nominal lumber, it is much faster and cheaper to produce, which means using OSB is a sure fire way to keep costs down.
Early versions of OSB were called waferboard and this sub-standard version gave OSB a bad name initially, but much of the performance issues have been eliminated with improved technology and manufacturing process.
Today you can find OSB in thickness from 7/16″ to 1 1/8″ for different applications from roof, wall, subfloor, I-joists and everything between.
Advantages of OSB
- More cost effective
- 2x greater shear strength than similar sized plywood (Source: University of Massachusetts)
- Meets most building codes for roof and wall sheathing
Disadvantages of OSB
- Edge swelling is common when exposed to moisture
- Sometimes made from wood species with poor rot resistance
- Rough texture not appropriate for finish work
- Provides minimal impact protection compared to plywood of equal thickness
What is Plywood?
Plywood is a sheet good commonly sold in 4×8 sheets consisting of multiple layers of veneer lumber bonded together with adhesives. Plywood is made with an odd number of layers for optimal strength and performance.
Up until 2000, plywood held the majority of the market for wall, roof, and floor sheathing when it was surpassed by OSB, which as of 2018, held about 75% of the market share.
One of the nice things about plywood is the variety of options you can buy. There are pressure treated grades, marine grades that can be used in water, fine hardwood options for finish work and cabinetry, pre-finished panels, or simple down and dirty 1/2″ CDX plywood. The bottom line is that there is a plywood for almost every application.
Advantages of Plywood
- Huge variety of options for every application
- Higher impact resistance compared to OSB (Source: FEMA)
- Better performance in high moisture applications
Disadvantages of Plywood
- More expensive than OSB (about 15% to 30% more)
- Significantly lower shear strength than OSB (Source: University of Massachusetts)
- Natural knots holes in inconsistent locations can cause soft spots
Which Should You Choose?
Well, how should I know? Seriously, it just depends on the application, so I’ll give you a couple ideas of which would work better in each application to get you rolling.
If you’re building a house, then I’m a fan of OSB for almost everything sheathing related. OSB is great for walls and roofs and for subfloors I’m particularly fond of an engineered wood panel similar to OSB called Advantech. The ZIPSystem is a great all-in-one OSB sheathing panel that has the building wrap already attached to it, so all you have to do it tape the seams.
One best practice for wall sheathing that I learned from Matt Risinger is to use pressure treated plywood as the lowest course of wall sheathing to help prevent rot, since that is the most prone to wetting.
This isn’t a big deal for most of the country, but hurricane preparation is one place that you want to make sure do it right since your life may depend on it. When you are boarding up for a big storm, you should be using at minimum 1/2″ CDX plywood. OSB does not provide adequate protection against fast moving storm debris.
My go to option for cabinets boxes and work tables surfaces is 3/4″ birch plywood. It is super smooth and sturdy and makes for a great work surface or a strong cabinet carcass. You can use pre-finished birch plywood to avoid having to paint the interior of the boxes and save a ton of time.
Sure you can bend nominal lumber if you want but building curved projects from multiple layers of 1/4″ finish plywood is a great way to get the job done inexpensively and quickly. I have built curved window jambs and other pieces of furniture by laminating 3 to 5 pieces of 1/4″ plywood together with my favorite wood glue.
Exposed Exterior Panels
For large flat surfaces wider than 12″ exposed to the weather like soffits, board and batten siding, or other decorative elements, there is really nothing better than marine grade plywood. Marine plywood is different from pressure treated plywood. It is not treated with chemicals to prevent rot, but rather, marine plywood is made with perfectly smooth layers and waterproof glue so that it can perform so well against water that you can build a boat from it!
Marine plywood still needs to be painted or finished with some sort of coating or it will not last because while the glue won’t fail, the wood fibers will be damaged by the elements.
There is a great video by Matt Risinger on the topic of OSB vs. plywood especially if you are comparing the two in regard to building and sheathing a house. You’ll get info about pricing and where to use which. Check it out below.
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.