Hardwood Flooring: The Basics

Hardwood flooring
Timber Floors/Flickr/CC 2.0.

Timber Floors/Flickr/CC 2.0

With the increased popularity of porcelain tiles, luxury vinyl, and plastic laminates—all of which can now be manufactured to look remarkably like wood flooring—genuine hardwood flooring has become slightly less common in recent years. But real hardwood flooring remains a premium flooring material that is still the preferred choice whenever a truly genuine look is required. After all, the goal of newer flooring products is to look like wood—no one develops a flooring material with the goal of making it look like plastic.

Solid Hardwood vs. Engineered Wood

A floor that appears to be solid hardwood may be exactly that—solid planks of a hardwood such as oak, maple, birch, or mahogany that fit together with tongue-and-groove joints and nails. But it is equally likely that the floor is made with a form of engineered wood—planks that have been manufactured by bonding a thin layer of real hardwood over 5 to 7 thin layers of plywood glued together with the grain direction alternating from layer to layer. This construction give engineered wood flooring remarkable stability and resistant to warping.

Advantages of solid hardwood flooring include:

  • Can be sanded and refinished several times over the lifetime of the floor
  • Thick flooring layers offers a solid feel underfoot
  • Sound transmission is better than engineered hardwood
  • Normally sold unfinished, so can be stained in any color desired

Advantages of engineered hardwood flooring include:

  • Extremely stable flooring especially when in contact with concrete subfloor
  • Cheaper than solid hardwood
  • Easier installation than solid hardwood; amateur DIY installation is possible
  • Generally sold prefinished, reducing work required for installation

Environmental Issues

Solid hardwood is a truly natural product, and disposal of old flooring is no problem when the floor ends its useful life. Many old solid hardwood floors are recycled for other purposes. Engineered hardwood floors, though they consist primarily of wood products, also use a variety of glues in the plywood layers that form the core. These adhesives may outgas formaldehyde or other toxins in small amounts, and people who are sensitive to these substances may experience health issues.

Subfloor/ Underlayment Requirements

Both solid hardwood and engineered hardwood flooring require solid, sturdy subfloors, and may require some form of secondary underlayment installed over the subfloor. In many cases, an existing old floor, if solidly attached and in good condition, can serve as the base for new solid hardwood or engineered flooring planks.

  • Wood subfloors of plywood or OSB are the standard underlayment for hardwood flooring. If they are in good condition, no interim underlayment is necessary. Otherwise, a thin secondary plywood underlayment can be laid down over the subfloor to create a solid base. Wood subfloors must be structurally sound and free from movement.
  • Concrete: When installing hardwood flooring on concrete, it must be at least 30 days old and must have passed all moisture tests. Engineered wood is considered a better choice for installation directly on concrete. Solid hardwood flooring can be susceptible to the moisture migrating through concrete, so it can be installed on a layer of plywood attached to sleepers laid on the concrete to isolate it from dampness.
  • Tile, or vinyl: Existing tile or vinyl flooring that is in good condition—well attached and perfectly flat—can be an acceptable base for laying new hardwood flooring. The thickness of multiple flooring levels can be an issue, though.
  • Laminate: Existing laminate flooring is usually not acceptable as an underlayment for new wood flooring. Laminates are usually floating floors that are not secure enough to serve as the base for new flooring. They should be removed before installing hardwood flooring over the subfloor.

Tools and Installation Methods

Most of the tool necessary for installing hardwood flooring are ordinary carpentry tools, although specialty nailers can be helpful and shorten installation time.

With most solid hardwood flooring, a layer of felt builder's paper is laid over the subfloor before the flooring is laid. Solid hardwood flooring is sometimes face-nailed down through the face of the planks and into the subfloor, though this is more common with softwood flooring. More often hardwood flooring planks are nailed down diagonally through the side tongue as each plank is installed. This allows the nails to be completely hidden as the groove on the next plank covers up the previous tongue. Pro flooring crews use specialty nailers that snug up the planks at the same time they drive the nails. Other than this, ordinary carpentry tools—table saws, power miters saw, jigsaws, and circular saws—are used to cut the hardwood planks.

There are more options with engineered hardwood flooring, as they can be laid with nails, staples, or glue. Or, they can be "floating" floors in which the planks are secured together with a proprietary type of "click-and-lock" variation of tongue-and-groove joinery. Glue-down types of require notched trowels and other specialty tools, and floating floors may require an interim layer of thin foam underlayment over the subfloor Engineered flooring planks are also cut with ordinary carpentry tools.


Costs of solid hardwood flooring run $5 to $10 per square foot for materials, plus another $5 to $8 per square foot for installation. Cost variations are dictated by the type of hardwood used, and some unsual woods can run higher than these averages.

Costs of engineered hardwood flooring run from $3 to $10 per square foot; installation costs can add $3 to $10 more per square foot. Cost variations in engineered hardwood are dictated by the type of surface hardwood veneer and its thickness. Thicker veneers cost more than thin veneers.

Pro Tips for Surface Preparation

Much of the success of any hardwood flooring installation depends on good preparation of the subfloor and underlayment.

  • Complete removal down to the subfloor is often best. Unless the existing surface is very well bonded, removal of the old floor is the best option.
  • Surfaces must be flat and smooth. Floor-leveling compound can be used to fill uneven spots. Install a plywood underlayment if the subfloor is not smooth and secure. Or perform necessary repair to the subfloor before installing flooring.
  • Test for any moisture issues, especially over concrete. Use a moisture meter to verify that moisture levels do not exceed 4 percent between hardwood and subfloor. A moisture barrier or raised underlayment may be necessary on concrete. Refer to flooring manufacturer's specifications, and do not install any wood flooring that is not designed for the moisture conditions of the room.
  • Test for pH (alkalinity) and calcium chloride before installing any wood flooring over a concrete subfloor.
  • Thoroughly clean and vacuum underlayment before beginning installation of flooring planks.
  • Where possible, remove baseboard foot moldings, doors, and door moldings before installing flooring.
  • Cover the subfloor completely with felt builder's paper to cover the sub-floor and trim the edges. On engineered flooring, thin layers of foam underlayment may be specified by the manufacturer.
  • Store the hardwood planks for several days in the area they will be installed before beginning. This will allow them to adjust to humidity conditions and can prevent later warping.

Pro Installation Tips

Professionals follow several common practices when installing either solid hardwood or engineered hardwood flooring planks:

  • To minimize chipping, use fine-tooth, carbide-tipped blade to cut hardwood flooring. When using prefinished engineered flooring planks, saw with finished side facing down to minimize chipping. A strip of blue painter's tape applied over the cutting line can also prevent chipping from saw blades.
  • Make sure to leave narrow expansion gaps at the walls. These gaps will allow for seasonal expansion of the wood; they will be hidden when base moldings are installed.
  • Using a tapping block to nudge flooring planks into position. Never strike the flooring planks directly with a hammer.
  • Follow the professional pattern of moving left to right as you install planks.
  • Follow the manufacturer's recommendations for removing any marks left on the planks during installation.