Amongst the many kinds of plywood available, is ACX plywood. This is a type of softwood plywood of a very high grade. While it is not a hardwood plywood, it is as if it is trying to compete with it. This is the highest grade of softwood plywood commonly manufactured, with a face-side surface which can be used for furniture or architectural applications where the wood is exposed and either stained and varnished or painted. It is essentially a cabinet-grade softwood plywood. There is also a AB softwood plywood rating, but it is rarely found.
The name “ACX Plywood” doesn’t refer to a specific type of tree or wood, although all softwood plywood is made of some variety of pine, fir or spruce. The name refers to the grade of wood, and glue, used to make the plywood product. It has nothing with strength, since it mostly depends on thickness. Grades are determined by the quality of veneer on the face and back of each plywood panel.
Almost all plywood has face and reverse sides, with the face side having a better finish than the reverse side. This better finish includes the number and size of knotholes allowed, whether or not splits are allowed and how smooth the finished surface is sanded (if it is sanded).
Softwood and hardwood plywood are graded slightly differently. In both cases, the face and reverse side are graded separately, with the face side listed first in the grading, followed by the reverse side. In hardwood plywood grading, the face side receives a letter grade, while the reverse side receives a number grade. With softwood plywood, both the face and reverse side is given a letter grade.
Since this is softwood plywood, both the face and reverse side are given letter grades.
To begin, the “A” refers to the face side of the plywood, which is always the better side. This side will have fewer noticeable blemishes, such as wood knots. “A” grade wood, specifically, is known for having very few defects or knots. If there are defects, they are usually fixed by inserting wooden plugs, adding synthetic patches, or synthetic fillers to provide a smooth, unbroken surface and turn the wood into an “A” grade wood. Also note these surfaces are always sanded to make them smooth enough to provide a good finish when painted.
The “C” side, or the back side, is of lower quality than the face. These wood panels often have several defects, including both open and closed knots, as well as cracks and splits. Wood discoloration is also common for this grade of plywood. Even so, the number and size of these defects is limited by specifications.
“A” and “C” grade plywood veneers are commonly seen on the same piece of plywood, since most projects only require one “good side”. The “good side” will always be the visible side, such as being used on the outside of a home, where it will not be covered by other material.
As with any plywood, ACX plywood is made of a number of layers of wood veneer. An odd number of layers is always used, with the face and reverse sides being laid in the same direction. Each adjacent layer is laid so that the grain is perpendicular to its neighbors, ensuring both strength and stability.
The various layers are bonded together with a rosin adhesive under pressure. There are a number of different adhesives used, but the ”X” used in this plywood’s rating shows us that a specific choice was made in the selection of the adhesive. The “X” means “exposure” and refers to the plywood being usable for exterior applications on a home, where it will be exposed to the elements while the home is being built and is not fully dried in yet.
Please note that even though this plywood is graded for exposure to the elements, that’s not advisable. While the adhesive used in the plywood can withstand moisture, the wood fibers themselves will soak up some water. This will happen mostly at the edges of the board, but can also happen along the face. Soaking up moisture in the face of the board will cause the grain to raise up, essentially eliminating the finely sanded surface, requiring sanding to smooth it back down.
Another important note is that “X” rated plywood really isn’t waterproof, as pressure treated plywood is. The wood fibers themselves will still decay if exposed to enough moisture, even if the glue still holds. This provision exists, indicating that the plywood can be used in architectural applications where the home is not yet dried in and there is a chance of it being exposed to moisture while the home is under construction.
Softwood plywood is predominantly used for construction purposes. Since ACX plywood is a higher grade material than say CDX plywood, it is specifically used in cases that require good appearance or a smooth finish, along with durability. Because this plywood is more expensive than other grades of softwood plywood, it is only used where needed, not in all situations. One important use for it is for subflooring, underneath vinyl flooring.
Although this is an exposure graded plywood product, it is rarely used for sheathing. All sheathing applications, whether in roofs or walls, will be covered by other materials, eliminating the need for the high quality appearance that ACX plywood provides. It should not be used in situations where the plywood is likely to be subject to moisture on a regular basis, such as for a shed. Using it for floorboards or for wallboards which will come into contact with the ground will guarantee that the plywood will rot within a few years, requiring replacement.
ACX plywood is an excellent choice for use by the handyman or do-it-yourselfer for projects around the home, including children’s furniture, workshop shelves and any other shelving or furniture which will be painted. The lower cost, when compared to hardwood plywood products, helps to keep the cost of these projects down, while
When used for children’s furniture, the smooth surface of the “A” face gives an excellent finish when properly primed and painted. If a lower grade of softwood plywood is used, in place of ACX plywood, the surface will not be smooth and will usually need to be filled, before sanding.
While ACX plywood is more expensive than lower grades of softwood plywood, it is still readily available, especially as “project panels” rather than full sheets. You may have to look around a bit, if you want to find full sheets. Some retailers, such as Menards, The Home Depot, or Lowes, may have these products available online, although I would imagine that shipping would be cost-prohibitive.
Check your area for vendors who specialize in selling architectural trim to contractors. They will often carry a better selection of plywood products, including ACX plywood and hardwood plywood, as both are used in cabinetmaking. Just avoid those vendors early in the morning, as that’s when most of the contractors go there. It might be a little bit difficult getting waited upon with all those contractors, many of whom are regular customers, in the warehouse.