Anatomy of Your Wood Frame Floor

Your home's wood frame floor includes many parts that add both to the stability of your home and to your comfort. Learn more below about such wood-frame floor parts as joists, subfloors, underlay and the best adhesives to use for specific floor coverings.

Live and Dead Load

The floor and walls of your home support weight known as live or dead load. The live load is the furniture and appliances you bring into the house when you move in. The dead load includes the permanent fixtures of the house such as plumbing, pipes, ventilation system and floor coverings.

Floor Joists

The floor joists are the cross beams that support your floor. They are made of 2-inch by 8-inch solid wood, or 2-inch by 10-inch, and are usually 16 inches apart at their centers. Both ends of floor joists are fastened into, and supported by load bearing walls or 90-degree angled beams.


The floor beams that support the joists may be made of solid wood or they may be steel.


The subfloor in a house whose main floor is above an open basement or crawlspace is made of plywood. Most building codes require that this subfloor be at least 5/8 inch thick. In a home built on a concrete slab with no open foundation or crawlspace, the subfloor is solid poured concrete.


An underlayment is necessary for carpeting, laminate flooring and some kinds of hardwood floors. The underlayment helps trap moisture that can cause mold growth in carpets and can warp wood floor paneling. Underlays with an aluminum vapor barrier can help stabilize and level an uneven subfloor surface. Specialized underlays have been developed to provide improved heat transfer and protection for floor surfaces installed over heated flooring systems. Other underlays insulate floors and reduce transmission of sound. You might want to install these underlays in second-floor bedrooms to make them quieter for sleeping.

Flooring Adhesives

The kind of flooring adhesive used will depend on the type of flooring you install above it. Use a solvent-based or urethane adhesive under a hardwood panel floor, a parquet floor or an engineered wood floor to prevent moisture seepage into the wood. Use a water-based low emission adhesive to secure carpet to a plywood subfloor. New types of heat-resistant adhesives have been created to add floor surfaces to heated floors. Ensure the subfloor surface is clean and level before applying adhesive for any floor covering.

Floor Coverings

From ceramic or terracotta tile to hardwoods in a range of types, your floor coverings will help unify and define the style of your home. Install durable floor coverings, such as tile or laminate, in areas where people walk most often and where spills may occur, such as the kitchen. Choose a soft and invitingly textured floor covering, such as carpeting or area rugs over hardwood, for family rooms and bedrooms.

Why You Need to Know About Your Wood Frame Floor

If you decide to install heavy furnishings in your home, such as encyclopedia bookcases or a 20-gallon aquarium, you need to know if your floor can support this concentrated weight.