What’s a roofdeck? Not to mention, you don’t necessarily need to pay the veneer that you will get with the CDX grade of plywood. This is because it is resistant to moisture and therefore, it will not be damaged; at least not for a very long time. OSB production in the United States and Canada totaled 25.4 billion square feet (3/8-inch basis), or 59 percent of the total combined production of structural plywood and OSB in 2004. While OSB can pack 50 strand layers into a sheet, plywood only has 5-7, giving OSB a more consistent density, though it does about two pounds or so more per sheet then plywood. Plywood is made with an odd number of layers for optimal strength and performance. I recommend that all roofdecks, especially in moist climates like Seattle, are CDX plywood and not OSB. Because the actual thickness may vary measuring the plywood is the only accurate way to determine its thickness. Think about how often panels get dragged on their edges across a truck bed or across the floor deck in the process of installing them. Both these manufactured sheets of wood are very essential in construction, and truth be told, you can hardly build your house without using at least one of them. One of the main grading systems when talking about the plywood is the smoothness of its front and back sides. While some people do prefer to go with traditional plywood, many construction experts make the argument that OSB is better for roofing. If you are asking why knowing their differences is so important, here is why. Don’t get frazzled and confused during the construction or repair of your home. He also holds a bachelor's degree in English from Iowa University. It is also used for roof sheathing. Here’s what you need to know. CDX is veneer plywood, which is manufactured by gluing and pressing together sheets of wood. VOCs in Plywood vs OSB. Now that we both agree that knowing the difference between the two is important, let’s start by knowing what they really are. The result is that the tendency for the boards to warp into their original shape is diminis… If you are building a home, one of your first choices you’ll need to make is which Sheathing to use for your walls. A plywood subfloor generally uses 1/2-inch to 3/4-inch-thick sheets of plywood that have one rough side (which faces down) and one smooth side, which faces up. At the end of the day, you should only really use CDX plywood for interior applications or surfaces that will not see much water. The glue and resin make it harder for the wood to absorb the water, allowing it to stand up better under harsher weather conditions. The sheets are generally 4 x 8 or 4 x 12 feet in size. However, in as much as CDX is more expensive in relation to OSB, generally, they are both affordable and easily available in lumberyards and stores. CDX and OSB are used for almost similar things, but because they have different features, one is better applied in some tasks and the other one on other tasks. The result is a wooden sheet that is proportionally as strong as steel, without the weight that comes along with concrete or steel. It is often less expensive than CDX plywood because this manufacturing process doesn’t require the same costly veneers found on the front and back of CDX plywood. Should they go with OSB vs. CDX plywood for the roof? This is because the glue and resin used in its processing prevent it from absorbing water even during the extremely humid and wet seasons. If you have to choose, you need to know the difference between CDX vs. OSB. OSB is ideal for these applications where the CDX simply will not work. Building codes recognize both plywood and OSB to be alike in their properties and use the phrase \"wood structural panel\" to describe them.However, plywood subfloors are stiffer than OSB by about 10%. Even though CDX is not waterproof and absorbs water easily, it also loses this water quickly and goes back to its original shape. Should you use CDX (plywood) or OSB (oriented strand board) for roofing plywood? While this may sound similar to CDX plywood, it is a very different composition process, and OSB board is generally much less durable than CDX plywood. On page 2 you will see the plywood sheathing info. Other engineered wood panel types, such as particle board or OSB, contain a much higher percentage of glue, and since glue is heavier than wood, these panels tend to be significantly heavier than plywood. Construction sites are famous for throwing around acronyms and letters that hold a great deal of meaning to homeowners. Unlike OSB, plywood has been developed into different types over the years in different ways to be used for different purposes. 225 Broadhollow Rd.Suite 310W Plywood and OSB manufacturers try to improve this by sealing the panel edges, but the sealant, whether it is a wax or a paint, tends to get scuffed off. Both plywood and oriented strand board (OSB) are equal in strength and durability. The National Roofing Contractors Association and the Asphalt Roofing Manufacturers Association both gave the thumbs-up of approval to use OSB for roof sheathing, provided that each sheet has approval from the APA – Engineered Wood Association. Plywood vs. OSB (Oriented Strand Board): Major Differences . Moisture resistance ... with less glue than plywood. In the end, many people opt for OSB because it is lower in price and more stable than CDX plywood. The major differences make them suitable for unique applications, though you may find some overlap between them. Press Esc to cancel. Even after losing the water, it will take time for it to go back to its original state. They are known as wood structural panels. OSB and plywood offer similar (and sufficient) performance in terms of strength and functionality, though plywood is about 7% stronger. (339.26 kB) Q: What are the concerns about VOC emissions from exterior plywood and OSB? ACX and CDX are both exterior plywoods and aren’t specifying the type of wood. OSB is best for substrate underneath shingles or decking. This can result in visible deflection of the panels between the supports and can telegraph through causing a wavy appearance to the roof. But take care, it also requires that you use water-resistant coating at the edges. The glue and resin that is mixed in with the wood chips makes it much less permeable, so OSB holds up longer in harsher conditions. COPORATE HEADQUARTERS This is because the glue and resin used in its processing prevent it from absorbing water even during the extremely humid a… Which is the better option, plywood vs. Advantech? In fact, recent price quotes from Denver, Boston and Atlanta put 7/16-inch osb $3.00 to as much as $5.00 per sheet lower than 1/2-inch cdx plywood. Before you can really grasp the different ways to use CDX plywood vs. OSB, it can help to have a better understanding of what each of them is. OSB absorbs water more slowly than plywood, which can be beneficial in areas of low dampness. Alternatively, OSB tends to be more waterproof than traditional plywood. This includes interior and exterior plywood of any thickness. Plywood Holds the Moisture Advantage Over OSB. OSB, on the other hand, stands for Oriented Strand Board which is a cheaper version of CDX. This means that the plywood allows being exposed to moisture, but just for a limited period of time A prolonged exposure will lead to water damage. OSB also seems to be good for roof sheathing. OSB holds up to water quite well, and it is easily seen as water-proof. CDX plywood is created by bundling layers of wood together. It may also make it more likely that the roof will rot over time. Alternatively, OSB tends to be more waterproof than traditional plywood. This is a question most people seem to seek answers to. In the case of CDX plywood, the X at the end denotes that it is rated for exposure. My personal opinion is that OSB performs well on the wall and floor but stick to CDX Plywood on the roof. Each layer is held in place by quality binders and adhesives. Since it will never be visible, it may just be a waste of money. However, once it has absorbed water, it dries more slowly. Structure or Basic Composition. If you are big on saving, then you would want to go with OSB since it is a cheaper version of CDX. This costs money and time, but knowing the difference between OSB and CDX does not. By Clayton DeKorne Download the PDF version of this article. Cover it on both occasions and maintain it regularly to ensure it does not get damaged. A: Clayton DeKorne, chief editor of JLC, responds: VOC emissions are pretty much a nonissue for exterior-grade plywood and OSB. This won’t imply the actual quality of wood itself, e.g. What is the difference between CDX and OSB? The National Roofing Contractors Association, the Asphalt Roofing Manufacturers Association. While plywood is generally limited to 8 to 10 feet lengths, OSB panels can be manufactured in lengths up to 16 feet. The biggest difference is how both react when exposed to large amounts of moisture over an extended period of time. However, it needs to be covered and protected long-term. On the other hand, OSB is produced very differently. Melville, NY 11747, Terms & Conditions The ‘best is classified by the least knots, shown grain, etc. But, as we have seen each one of them has its strengths and weaknesses, making each one of them, best for different tasks. OSB is now used for about 70 percent of all floor, wall and roof sheathing in North America. It isn’t ideal to use for sheds, roofing, or other areas that see consistent rain. first, i would just go with cdx but i just started college so money is a bit tight, anyway my room is small (still living with my parents) and im thinking about putting a floor in my attic to give my self some more room. than CDX plywood. It isn’t ideal to use for sheds, roofing, or other areas that see consistent rain. Plywood is often sold in 1 / 4 “, 1 / 2 “, or 3 / 4 ” nominal thicknesses, but the actual thickness is often 1 / 32 ” thinner. As mentioned above, the X in CDX stands for exposure. In 2001, oriented strand board surpassed plywood in terms of square footage produced. When choosing a new roof, don’t forget to consider what surface the roof will nailed onto. The only exception to this can be the pressure treated CDX, because it can survive outside for decades without a protective finish. But, there is an exception to pressure-treated CDX; they can withstand extreme moisture without getting water damaged. Many of these abbreviations that you hear will represent different types of plywood that are used for subflooring, roofing, and everything in between. Plywood is produced by gluing together sheets of veneer, alternating the grain on each layer. Well, when used as exposed decking or subflooring each has its strengths and weaknesses. When it dries, it is more likely to return to its … AC is used when a very nice finish is necessary. Each layer is placed on top of the other with the graining running in the opposite direction for the opposing layer. OSB is much more waterproof than plywood and CDX plywood. OSB vs Plywood: Fast Fact. comparing the quality of luan and pecan tree, but rather the finish of surfaces. Because plywood is rated as shop grade because of defects, almost any type of plywood can end up in the shop grade bin. Although, OSB typically offers a higher shear rating which adds rigidity to your structure. While you may want to consider a different type of roof sheathing, CDX plywood is still not a great choice for your roof. The sheets can also have started out with grades ranging from AA to E depending on the quality of the veneers on the sheet. Sherwood Lumber uses cookies to ensure that we give you the best experience on our website. Plywood is composed of approximately 92% - 97% wood, with the remainder made up by primers, sealants, and adhesives such as phenol formaldehyde resin. However, OSB does not absorb water easily, but when it does, it takes quite a while to lose the water. Are there any roofing situations where osb should NOT be used? If you continue to use this site we will assume that you are happy with it. CDX PLYWOOD vs. OSD PLYWOOD OSD and CDX plywood are both commonly found on construction sites, because builders and contractors rely on both types of plywood to get the job done. For example: Marine plywood is more moisture resistant than standard plywood, is better used in constructions where exposure to water is likely (e.g. There are real differences between the various grades of plywood. Each of these materials has its own unique properties and qualities, and so each is used in specific applications. Specializing in building and renovating homes, Thomas Luttrell has worked in homebuilding since 2002. Secondly, OSB panels have a higher shear rating than plywood panels and are thus often installed with greater spans than plywood of the same thickness. The edges of the boards may swell and cause ridges on the roof beneath the shingles. Type above and press Enter to search. 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. Imagine when you want to do your subfloor or roof sheathing and you confuse the two, then two months later, the wood start cracking and rotting, due to water damage. It is made of wood chips, resin and glue, cast and baked together to produce a CDX-like sheet. It is only manufactured to hold up to water for a short period of time. You will need to remove everything and start all over or ask a specialist to correct the mistake. But, there is an exception to pressure-treated CDX; they can withstand extreme moisture without getting water damaged. Making the right choice is easy when you understand the inherent differences between these starkly distinctive types of materials! The main difference between the two is how they handle moisture, and oddly enough there are wildly varying conclusions - from very reputable sources - as to just how vapour permeable they are. For a decking, or substrate underneath shingles, you can usually use either material. A 3 / 4 ” sheet is actually 23 / 32 ” thick. However, you will want the finished veneer of CDX for projects like cabinets and furniture. Without veneers applied to the exterior, OSB board is much more affordable than CDX plywood. One of the main areas that people tend to run into these issues is when they are trying to find plywood for their roofing. This means that the plywood allows being exposed to moisture, but just for a limited period of time A prolonged exposure will lead to water damage. Because the adhesive and resin make it more difficult to absorb water, OSB is less likely to expand and contract with exposure to moisture. As mentioned above, the X in CDX stands for exposure. To get more informed insight on which one to use for what, you can always ask an expert. Depending on your location, you might find that it is roughly half the price of more traditional CDX plywood. Far too often I see OSB “sag” between the trusses making your roof look wavy. What is the Actual Thickness of a Sheet of Plywood. Others, however, prefer to stick with plywood. Both oriented strand board (OSB) and plywood are considered the same by building codes. OSB or CDX plywood for subflooring? CDX plywood is produced by gluing together sheets of veneer, with each layer being glued the opposite grain to the one below it. One of the nice things about plywood is the variety of options you can buy. Learn how to tell these two apart and how to use each one. The major distinction between these categories is the actual construction of the sheets. Plywood vs. OSB Protect an unfinished home from the elements—and a finished home from the consequences of plumbing disasters—by starting with a … That is why OSB is sometimes used to secure houses when a hurricane draws near. On page 6 is OSB Sheathing info and a 24/16 L/180 has a uniform load of 68 at 24″o.c. The first piece of wood is placed so that it rolls “up” while each subsequent layer is laid 90 degrees to the one below it, and upside-down. While CDX is strong and will give good results, it is important that you take care of it. OSB and plywood vary in terms of durability. At the end of the day, you should only really use CDX plywood for interior applications or surfaces that will not see much water. Oriented strand board (OSB) and plywood are wood structural panels made by compressing and gluing pieces of wood together. Plywood is made by cutting thin layers of a tree all the way around its circumference. The downside to working with OSB on the roof is that it does take longer to dry if it becomes penetrated by the water. This comes as a surprise to many consumers because OSB looks simply as if lots of pieces of wood were glued together. It also warps or swells after water absorption and will not return to its original shape. © 2020 Sherwood Lumber Company. Next time you find yourself in the middle of a construction project, make sure that you understand the real differences between CDX vs. OSB plywood. The letters C and D represent the grades of either side of the plywood, while X stands for exposure. Trubord 7/16 is rated 24/16 and 15/32 and 1/2 are rated 32/16. This price spread means that a builder can save $700.00 on a 2,500 square foot house if osb is substituted for plywood sheathing on floors, walls, and roofs. The protection of the shingles isn’t likely to be enough to prevent the plywood from becoming warped and delaminated over time. The roof deck is the surface underneath your roof and roofing underlayment. This is to prevent the wood from absorbing water because when they do. Within 10 … OSB holds up to water quite well, and it is easily seen as water-proof. If you are not among the people searching for such answers, then you should be because it is important to know what the two are and their differences. These boards are then laminated together using a hot press (basically a giant iron that fuses wood and glue together under heat). Is Rain on a Steel Roof Louder than on an Asphalt Roof? This makes its dimensional stability better. However, there is one area of concern in which plywood beats OSB. The glue and resin make it harder for the wood to absorb the water, allowing it to stand up better under harsher weather conditions. Save my name, email, and website in this browser for the next time I comment. Despite these disadvantages, OSB is still commonly used for roofing. While OSB and plywood appear similar and are generally interchangeable, the different ways that each material is manufactured contribute to … CDX is used as an upgrade over OSB aesthetically, but no, it’s not winning any beauty contests. Plywood absorbs water more quickly, but it also dries more quickly. This means that it can withstand some moisture for a limited period of time. In such places, it does not get in contact with a lot of moisture, which prevents it from getting damaged. Oriented strand board (OSB) combines wood chips, glue, and resin into the shape of a sheet of plywood and bakes them together. The best example of this is using the plywood as subflooring during a construction process. While construction codes regard all materials similarly as "structural panels," the structure of the plywood and the oriented strand board (OSB) is somewhat different. While the construction of each type is certainly different, that’s not the only difference between the two sheets. CDX vs OSB sheeting. BY SEAN GROOM Drawings this page: Don Mannes. Plywood for the Roof: What Should You Choose. There you will see that a 24/0 plywood panel has a uniform load at L/180 of 57 at 24″o.c. ACX, CDX, and BB Formply are the most common types of plywood sold. L Plywood vs. OSB New-generation structural panels mean decade-old notions are no way to choose sheathing. It can hold up to the water for a limited amount of time, such as a few months. Determining how well they can hold up to water also determines what types of applications each one is best suited for. Similarly, there are major differences between plywood and OSB. Some design and construction professionals have come to swear by oriented strand board. (Most people mistakenly think that it stands for “exterior”.) CDX is best for sub-flooring. This provides an inherent system of checks and balances that makes plywood a relatively stable material. As a result, OSB floors are more li… CDX plywood. 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