Subfloors and Underlay (16)

When building a new home or remodelling a structure, a subfloor is the ideal base for a new floor. It provides a foundation that supports the top layer and protects it from damage. Subfloor plywood is extremely strong and can support most floor types including plywood and treated plywood. Additionally, underlayment plywood is a middle layer that keeps moisture from reaching the surface. For optimal and long-lasting results, consider all three components when installing a new floor.

---

Installing a top layer of hardwood, tiles or linoleum on your floor is only part of the job. It’s important to first lay down a layer of subfloor plywood. This prevents the floor from sagging and helps to increase its overall life.

Underlayment plywood is a different material than that used for other applications, such as deck panel plywood. It’s designed to hold up to the pressure of foot traffic. Without this additional layer of OSB plywood, the top floor would succumb to this pressure and have a shorter usable life.

When laying down carpet, it’s also a good idea to install an underlay. This layer goes between the carpet and the subfloor plywood. It pads the carpet for added comfort and resiliency and provides another barrier against moisture getting under the floor. Since the cold can seep into a home through the floor, a layer of special floor insulation can make the home less susceptible to energy loss. This prevents cold floors in the morning and can save on heating and cooling costs throughout the year. Underlayment plywood comes in different thicknesses. Use the thicker varieties for harder floors and the thinner pieces for carpeting.

One issue that homeowners face is uneven subfloors. This can result in uneven flooring, and can create gaps between the bottom layer and the surface. Because subfloor plywood installs directly over the joists, improperly levelled joists can cause the whole floor to be off. A quick and simple solution is to install levelling shims. These raise up the underlayment plywood without the need to plane down the joists or to make other fixes. Proper installation requires the application of adhesive to the joists, before screwing or nailing, so get wood glue and fasteners when ordering materials.