Anyone who has ever observed how a house is built knows that framing the structure is one of the early steps in the process. Once a house is fully framed, the builder’s next step is to add exterior finishes such as plywood and wrap and, inside, lay the subfloor. The builder also completes the roof early on in the process so the inside of the structure is protected from the elements.

Protecting the subfloor inside the house is important because too much exposure to rain and dampness can negatively affect the subfloor material. And, while protecting the flooring before construction is complete is important, so is using a subfloor type that minimizes damage to a floor in the event of a flood or plumbing disaster after the home is built.

Not all subflooring panels are created equal, however. The different types of materials that can go into a particular type of floor, as well as the manufacturing and engineering processes used to make the floor panels, mean subfloor types differ on a variety of characteristics and qualities. The most common subfloor products used are plywood and oriented strand board (OSB). A third type, AdvanTech®, is also popular among builders. Here we examine all three types of subfloor material.

What is plywood?

To make a sheet of plywood, thin strips of wood veneer – usually at least three – are glued together and placed in layers at alternating 90-degree angles. The wood is then hot-pressed and bonded together. The end result is a layered material with an improved structure that resists the normal expansion, contraction, and warping that occurs with solid wood. In other words, plywood is stronger and more stable than solid wood lumber, and also uniform in strength. The downside is when plywood gets wet, for example in the construction phase, the edges soak up the moisture and swell. This results in extra work for the builder, who must go back and sand the edges to flatten the floor board again.

Plywood can be made from different wood types, with the most popular being oak, mahogany, and birch, each with a varying degree of strength. But, plywood thickness can vary by as much as 1/32” from the stated thickness. To counter potential issues and ensure consistency with plywood thickness, it is always advisable to buy the full amount needed for the project at one time.

What is OSB?

Oriented strand board – OSB – like plywood, is made of layered and cross-laminated wood. But the strands of wood measure three to four inches, which is much smaller than the sheets used in plywood. Additionally, OSB is denser and heavier than plywood, as it can be made from up to 50 evenly compressed strand layers. Given its density, OSB absorbs less moisture than plywood, but when it does, the edges can swell just as occurs with plywood. And, OSB takes longer than plywood to thoroughly dry.

Manufacturers have taken steps to address moisture absorption in both plywood and OSB by adding water-resistant sealing to the edges. The seal can, however, degrade or be lost altogether as panels are cut or moved around.

What is AdvanTech®?

AdvanTech is a highly dense engineered wood. AdvanTech’s qualities combine strength, stiffness, and moisture resistance.

AdvanTech is specially engineered so that the layers create a “woven matrix of fibers.” This process makes the product stable throughout, which means it is less prone to squeaking. And its dense composition means nails/fasteners hold better than they do with plywood or OSB.

To protect against warping or swelling from water or other moisture, moisture-resistant resin is applied to every strand of wood that goes into the flooring. This step makes AdvanTech more moisture resistant than both plywood and OSB.

AdvanTech costs more than plywood and OSB, but some professionals believe the extra cost is worth it – given the product’s qualities of strength, consistency, ease of use, stability, and moisture resistance.

Plywood, OSB, and AdvanTech are all popular choices for subfloors. When deciding which to use, it’s important to take all qualities into account. If necessary, speak to a professional for a recommendation on the best type of subfloor material for your project.

Steve Rush of Sovereign Construction Services knows all there is to know about the different types of subflooring materials available. His years of experience in the home building and remodeling business mean he can make the most appropriate recommendation for your home. If you are thinking about building new, or replacing a floor in an existing home or addition, call Steve today at 610-639-2986 for a free consultation.