Hardwood Floor Installation: Nail-Down, Floating, and Glue-Down Methods

Acclimation

Wood flooring must acclimate to your home's humidity and temperature before installation. Stack the flooring in the room where it will be installed for a minimum of 3 days — 7 days is better. Leave the bundles open so air circulates around the planks.

The room should be at its normal living temperature and humidity during acclimation. Running the HVAC system is essential. Do not acclimate flooring in an unheated garage or a freshly drywalled room that has not dried.

Check the moisture content of both the flooring and the subfloor with a pin or pinless moisture meter. For solid hardwood over plywood, the moisture difference between the flooring and subfloor should be within 2 to 4 percentage points. A larger gap means the wood will move significantly after installation.

Subfloor Preparation

The subfloor must be flat, clean, dry, and structurally sound. Check for flatness with a 6-foot straightedge. The floor should be flat within 3/16 inch over 6 feet. High spots can be sanded down. Low spots can be filled with floor leveling compound.

For plywood subfloors: walk the floor and mark any squeaky spots. Screw those areas down with 2-inch screws into the joists. Squeaks under hardwood flooring are nearly impossible to fix after installation.

For concrete subfloors: test for moisture using a calcium chloride test kit or a concrete moisture meter. Concrete must read below 3 pounds per 1,000 square feet per 24 hours (calcium chloride test) or below 75 percent relative humidity (in-situ probe). High moisture readings require a moisture barrier.

Remove existing baseboards and door casings. Undercut door casings with a jamb saw or oscillating tool set to the thickness of the new floor plus underlayment. The flooring slides under the casing for a clean look without gap-filling.

Nail-Down Installation

Nail-down is the standard method for 3/4-inch solid hardwood over plywood or OSB subfloors above grade. You drive cleats or staples through the tongue of each board at a 45-degree angle using a pneumatic flooring nailer.

Rent a pneumatic flooring nailer and mallet. The first 2 to 3 rows must be face-nailed and drilled because the flooring nailer cannot operate close to the wall. Pre-drill holes to avoid splitting, and fill the nail holes with color-matched wood filler.

Start along the longest, straightest wall. Snap a chalk line 3/4 inch from the wall (this gap is the expansion space, hidden by baseboard). Lay the first row with the tongue facing the room, groove against the wall. Face-nail this first row.

Work across the room, driving cleats through each tongue. Rack the boards — stagger end joints by at least 6 inches between adjacent rows. Avoid H-patterns where end joints align in every other row.

The last 2 to 3 rows also require face-nailing because the flooring nailer will not fit. A pry bar pulls the last row tight against the previous one while you nail.

Floating Installation

Floating floors are not attached to the subfloor. The planks lock together with a click-lock or tongue-and-groove system and the assembled floor floats on an underlayment pad. This method works for engineered hardwood over any subfloor type, including concrete.

Install the underlayment first. For concrete, use a combination underlayment with a built-in moisture barrier. For plywood, a standard foam underlayment provides cushion and sound dampening. Overlap the seams and tape them.

Leave a 3/8-inch expansion gap along all walls and fixed objects. Use spacers. This gap is critical — a floating floor that is pinched between walls will buckle.

Angle the tongue of each new board into the groove of the previous row at about 20 degrees, then press down to click it into place. Use a tapping block and mallet for stubborn joints — never strike the exposed edge directly.

Floating floors feel slightly different underfoot than nailed floors. There is a subtle hollow sound when walking that some people find objectionable. A quality underlayment reduces this effect significantly.

Finishing Touches

Reinstall baseboards to cover the expansion gap. If you plan to paint the baseboards, do it before installing them so you do not get paint on your new floor.

Install transition strips at doorways, where the hardwood meets other flooring types, and at any change in floor direction. T-molding, reducers, and stair nosing each serve a specific transition purpose.

Wait 24 hours before moving furniture back. Use felt pads on all furniture legs. Do not drag furniture across the new floor — lift and place.

Frequently Asked Questions