Every flooring system is actually a complex system of multiple layers: structural joists, subfloor, underlayment and floor coverings. These structures carry the weight of several components, such as interior walls, furniture, appliances and the floor itself.
Joist is the first component of the flooring system. It is located at the bottom, and supports the weight of the entire floor. The joist system is the series of parallel structural members that run between beams or load-bearing walls and which holds up the entire floor. Over the subfloor, there is an underlayment that smooths out the subfloor and provides a flat, level surface for the finished flooring surface. Underlayment is used in some flooring systems as a smooth flat surface for the subfloor. Floor covering is the decorative top layer of flooring. The floor covering is the visible, decorative surface that you walk on—the hardwood planks, stone or ceramic tiles, vinyl tiles or sheets, carpeting, laminate planks, etc.
Subfloors are essentially the important structural layers upon which the decorative flooring rests. It is the structural component of a building that provides rigidity to the floor structure, supports live loads, and serves as the surface to which floor finishes can be applied. They serve to support the floor finishes and in some cases, they include the layers that separate the main structural parts of the floor from decorative floor coverings. Some form of subfloor is found beneath every type of floor, whether it is hardwood, carpet, ceramic tile, natural stone, vinyl, or laminate, and choosing the right subfloor material and installing it correctly is the key to a great floor that performs well. We have focused on different types of subfloor materials used in construction.
Types of subfloors materials
There are five types of subfloor materials each of them is discussed below.
Plank subfloors are usually made up of 3/4″ thick x 4-8″ wide southern yellow pine boards. Installation usually consists of nailing these boards to the floor joists. Since this type of sub flooring is usually found in older homes and can loosen up over time from the boards expanding and contracting, it is very important to remember to re-secure these planks to the floor joists using 2-1/2″ deck screws prior to installing any floor covering, as loose or damaged boards will affect the performance of the finished flooring. Many remodeled homes have wood plank subfloors covered with particleboard or hardboard underlayment to help bridge variations among the boards and create a flat surface for carpet and vinyl flooring.
Plywood is made from glued thin strips of wood veneer (called plies) that are layered at alternating 90-degree angles and placed in a hot press; the resulting cross-laminated and layered material is structurally enhanced and resistant to the expansion and contraction that affects solid wood. Plywood has been a standard subfloor material since the 1950s and remains the preferred subflooring for many builders. Standard plywood can be used for subfloors, but a better material is 3/4-inch tongue-and-groove plywood subflooring. The tongue-and-groove edges interlock to resist movement along the panel edges and create an overall stiffer floor.
Plywood subflooring also comes in 1/2-inch and 5/8-inch thicknesses. Thinner subflooring may be suitable for carpet or resilient floorings, such as vinyl or linoleum, but thicker subflooring is recommended for nail-down hardwood and is required for floor tile.
When OSB came on the scene as an alternative to plywood, detractors were quick to point out its deficiencies. Its affordable price aided its growing popularity, and it soon surpassed plywood as builders’ choice in home construction—floors as well as wall and roof sheathing.OSB stands for oriented strand board. OSB has the appearance of giant cornflakes pressed together to form structural panels in sizes similar to plywood, such as 4′ x 8′ x 5/8″.OSB subfloor is mostly serving as a base under the finish floor (hardwood, engineered wood, vinyl tile, etc.) and even below the underlayment, in some cases. A few builders say that they prefer OSB over plywood for flooring because the surface (when new) is always clean, flat, and knot-free. Many contractors find OSB to be a more consistent product than plywood or other types of material for subfloor: every sheet is the same. OSB compacts as many as 50 layers of strands into a single sheet the same thickness as that plywood, ensuring a much denser—and heavier—product throughout.
A concrete slab makes for a very hard, solid, durable, and often very smooth subfloor. Tile and stone flooring can be installed directly over concrete, but most other flooring materials require some kind of underlayment and/or a moisture barrier laid over the concrete. Concrete slabs usually consist of a 4-6″ thick, 3,500-5,550 lb strength concrete pour. Water used within the mix of newly poured slabs can take up to 3 months or more to dry out. Moisture testing should be performed prior to any installation of hardwood flooring.
Water is an inherent part of the hydration process of concrete. However, allowing excess moisture to leave the slab after it’s poured is crucial to a successful flooring installation. Once the slab is poured, the excess moisture must leave the slab in order to strengthen the concrete bond. The slab must also dry to a specified level of moisture before flooring materials can be installed on top of it. Moisture-related damage to the flooring materials is possible. Concrete slabs need to be flat. Use a self-leveling cement type floor leveler to fill any depressions within the slab and allow to dry before installing any flooring.
There are cases in which a concrete slab is paired with plywood or OSB elements to create a composite subflooring. One method includes fastening 2”sleepers over the concrete and covering them with plywood subflooring. Another method consists of laying down a floating subfloor made with tongue-and-groove OSB panels, adhered to a base layer of plastic or rigid foam insulation. This base serves as a moisture barrier from concrete dampness, and OSB works as a flat subfloor ready for finishing layers.
Lower-quality subflooring can swell or delaminate when exposed to water during construction. This can create uneven panels, which can lead to loosened connections and bonds over time, increasing the chance of squeaks. Sanding swollen, uneven panels during construction is a common practice, but it can cause costly construction delays. Current building code standards are designed to make sure floor systems can adequately resist the weight of a given design. However, they are not necessarily written to specifically eliminate squeaks, bounce or uneven floors. Proper installation plays an important part in flooring performance, as does choice of material. By using high-performance materials in critical unseen places, builders and their clients can improve long-term flooring performance. Choosing subflooring with code strength, stiffness and fastener-holding-power values can help reduce construction delays and minimize the risk of callbacks for squeaky, bouncy floors.