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

Hardwood floors are one of the most enduring home improvement investments you can make. They add warmth, beauty, and real estate value in a way that no other flooring material quite replicates. They also last for generations — a well-maintained hardwood floor can be sanded and refinished multiple times over a century of use.

Installing hardwood floors yourself is a project that is well within reach for a capable DIYer. The tools are accessible (many can be rented), the techniques are learnable, and the results — a room-length run of tightly fitted, beautifully finished hardwood — are deeply satisfying. This comprehensive guide covers every method of installation, the species decisions you need to make up front, and the finishing options that complete the project.

Choosing Your Wood Species

Before you think about installation method, choose your species. Different species vary significantly in hardness, grain pattern, color, and cost.

Janka Hardness Ratings

The Janka hardness test measures the force required to embed a steel ball halfway into a wood sample. Higher numbers mean more resistance to dents and wear — important for high-traffic areas.

Species	Janka Rating	Character
Pine	870	Soft, warm, rustic; dents more easily
Walnut	1010	Dark, rich; slightly soft but premium look
Red Oak	1290	Most common; warm, open grain
White Oak	1360	Slightly harder than red; tighter grain; very popular
Maple	1450	Hard, light, close-grained; shows scratches less
Hickory	1820	Very hard; dramatic grain variation

Red and white oak account for the majority of hardwood floor sales in the US. They are available in every region, come in a wide range of grades and widths, are easy to work with, and accept stain readily. If you are unsure what species to choose, start here.

Walnut is increasingly popular for its rich, dark color and modern aesthetic. It is softer than oak and more expensive, but stunning in the right home.

Maple is the floor of choice for gyms, basketball courts, and high-traffic commercial spaces. It is very hard and very light — nearly white — which makes it less popular for residential use but excellent where durability is the top priority.

Hickory is the toughest of the common species. Its dramatic grain variation is not for every home, but it is virtually indestructible underfoot.

Solid vs Engineered Hardwood

Solid hardwood is exactly what it sounds like: a plank of solid wood, typically 3/4” thick, 2-1/4” to 5” wide. It can be sanded and refinished five to seven times over its life, making it a true lifetime floor. Solid hardwood is moisture-sensitive and should not be installed in basements, over radiant heat, or in humid climates without careful moisture management.

Engineered hardwood has a real hardwood veneer (1/12” to 1/8” thick) bonded over a plywood core. The cross-grain construction of the plywood core makes engineered hardwood dramatically more stable than solid — it moves less with humidity changes, can go below grade (in basements), and works over radiant heat systems. The trade-off: it can only be sanded one to three times depending on veneer thickness.

For most nail-down installations, solid hardwood is the traditional and most durable choice. For glue-down and floating installations over concrete or over radiant heat, engineered hardwood is often the better technical choice.

Acclimation: The Step Most People Skip

Acclimation is non-negotiable. Hardwood expands and contracts with changes in humidity. If you install flooring before it has acclimated to the conditions of your home, it will expand or contract after installation — causing cupping, crowning, gaps, or buckled planks.

Bring all flooring into the room where it will be installed. Open the bundles or boxes and stack them with spacers between layers (or lay them out across the subfloor) for a minimum of five to seven days. The flooring should reach the same temperature and humidity as the living space.

Before and during installation, maintain the home at 65-75°F and 35-55% relative humidity — the same conditions the floor will live in long-term. Check moisture content of both the flooring and the subfloor with a moisture meter. The difference between the two readings should be 4% or less (2% or less for wider planks).

Subfloor Requirements

Your subfloor must be:

Flat: No more than 3/16” variation over a 10-foot span. High spots must be sanded or planed down; low spots filled with floor-leveling compound.
Dry: Concrete must test below 3 lbs of moisture per 1,000 sq ft per 24 hours (MVER test) or below 75% RH. Wood subfloors should be below 12% MC.
Structurally sound: No squeaky, spongy, or delaminated sections. Fasten any loose areas with screws before installing flooring.
Adequate thickness: For nail-down over joists, the subfloor should be at least 3/4” thick (combined with any underlayment). Thinner subfloors need reinforcement.

Installation Method 1: Nail-Down

Nail-down is the traditional installation method for solid hardwood flooring over wood subfloors. It is the most secure attachment method and the standard for 3/4” solid hardwood.

What You Need

Flooring nailer (pneumatic or manual): This is the key tool for nail-down installation. A pneumatic flooring nailer uses a rubber mallet to drive cleats or staples through the tongue of each plank at a precise angle, securing the floor while remaining completely hidden. Renting a flooring nailer is the most cost-effective approach for a one-time installation; purchasing makes sense if you plan multiple projects.
Pneumatic compressor (if using pneumatic nailer)
Circular saw and jigsaw for cuts
Rubber mallet
Chalk line and tape measure
Finish nailer (for first and last rows)
Pull bar and tapping block

Step 1: Install the Moisture Barrier

Roll out 15 lb. asphalt felt paper (or purpose-made flooring underlayment) over the entire subfloor, overlapping seams by 4”. Staple every 6” along the edges and every 12” in the field. This moisture barrier slows vapor transmission from the subfloor and provides a small amount of sound deadening.

Step 2: Establish Your Chalk Lines

Snap a chalk line parallel to the longest, straightest wall — or, more accurately, parallel to what you want the flooring to run parallel to (this may not be the same wall). Check that your starting line is parallel to the room’s main axis by measuring from two points on the line to the corresponding wall. Adjust until the measurements are equal.

For most rooms, you want the flooring to run the length of the room (parallel to the longest walls) and parallel to the main doorway or focal point.

Step 3: Install the Starting Row

The starting row is face-nailed (nails through the face of the board, near the wall, where they will be covered by baseboard) and also blind-nailed through the tongue. Pre-drill face nail holes to prevent splitting. Use 2” finish nails or cut nails.

Position the first row with the groove side facing the wall and a 1/2” expansion gap between the board and the wall. The expansion gap allows the floor to expand and contract without buckling. It will be hidden by the baseboard.

From the second row onward, use the flooring nailer. Position the nailer over the tongue of the board, align with the proper angle, and strike with the rubber mallet. The nailer drives a cleat or staple through the tongue at a 45-50 degree angle, completely hidden by the next board’s groove.

Work across the room in a staggered pattern. Stagger end joints by at least 6” between adjacent rows — and 1-2” minimum from joints in the row beyond that. Random-looking stagger patterns look the most natural.

Use the tapping block (a piece of flooring scrap with the groove removed) to tap each row snug against the previous one before nailing. The fit should be tight with no gaps.

Step 5: Face-Nail the Last Rows

As you approach the far wall, the flooring nailer will not fit. Switch back to face-nailing the last two or three rows, as you did with the first row. Use a pull bar hooked over the groove edge to pull each piece tight while nailing.

Cut the final row to width if necessary, maintaining the 1/2” expansion gap at the wall.

Step 6: Install Transitions and Trim

Re-install baseboard (or install new baseboard) to cover the expansion gap at all walls. Do not nail baseboard into the floor — nail only into the wall. The baseboard must be free to move with the wall while the floor moves independently.

Install transition pieces at doorways and between different flooring materials:

T-molding: Where two floors of the same height meet (e.g., hardwood to hardwood)
Reducer: Where hardwood transitions to a lower floor (e.g., hardwood to tile)
Threshold: At exterior doorways
Stair nose: At the top of staircases

Installation Method 2: Glue-Down

Glue-down is used primarily for engineered hardwood (and sometimes solid) over concrete subfloors, or over any subfloor where nailing is not practical.

The Adhesive

Use a urethane flooring adhesive — specifically formulated for hardwood flooring. Do not use construction adhesive or other general-purpose adhesives. Urethane adhesives remain slightly flexible after curing, allowing for the natural movement of the wood.

Moisture-cured urethane is the most common type. It requires a moisture barrier to be applied to the concrete first if the concrete moisture content is above acceptable limits.

Working time varies by adhesive type and temperature — typically 30 to 90 minutes. Work in manageable sections.

The Trowel

Use the notched trowel specified by the adhesive manufacturer. Trowel size (notch depth and spacing) determines how much adhesive is applied — the wrong trowel leads to voids (too little adhesive) or squeeze-out (too much). A 1/4” x 1/4” V-notch is common, but always follow the adhesive manufacturer’s specification.

Step-by-Step

Apply adhesive to a manageable section of the subfloor (no more than you can cover in the working time).
Wait for the adhesive to tack up (5-20 minutes depending on temperature and product).
Lay flooring planks into the adhesive, pressing firmly. Use a rubber roller or flooring roller to fully embed planks.
Work section by section across the room.
Tape planks together (masking tape) across the top to hold rows together while adhesive cures.
Allow full cure time (typically 24-48 hours) before walking on the floor and removing tape.

Installation Method 3: Floating (Click-Lock)

Floating installation requires no nails and no adhesive. The planks lock together at the edges and float over the subfloor as a single connected assembly. This makes it the fastest installation method and the only one that a complete beginner can realistically do solo in a day.

Floating is used for engineered hardwood with a click-lock profile and for laminate. It is not suitable for solid hardwood.

Underlayment

Install a foam or cork underlayment over the subfloor first. This provides cushion underfoot, slight sound deadening, and a small amount of vapor barrier function. Many engineered products now come with underlayment pre-attached — do not double up if yours does.

Installation

Lay the first row with the tongue side facing the wall (or groove, depending on the product’s click system). Maintain a 3/8” to 1/2” expansion gap at all walls.
Click subsequent planks into place: for most systems, angle the short end of each plank into the previous plank’s groove, then lower it flat to engage the long side lock.
Stagger end joints as with nail-down installation.
Use spacers against the walls to maintain consistent expansion gaps throughout.
Cut the final row to width with a circular saw or pull saw.

Important: Do not attach floating floors to the subfloor, walls, or any fixed structures. The entire floor moves as a unit, and restricting movement causes buckling.

Sanding and Finishing In-Place vs. Pre-Finished

Pre-finished hardwood comes from the factory with stain and aluminum oxide-reinforced finish already applied. It can be walked on immediately after installation, has no finish fumes in the home, and the factory finish is generally more durable than anything you can apply on site. The trade-off: micro-beveled edges between planks create visible lines and catch dirt; you cannot change the color later without replacing the floor.

Site-finished hardwood (unfinished boards finished after installation) produces a perfectly smooth, level surface with no bevels between planks. It looks truly seamless and can be stained any color. The process involves sanding the entire floor with a drum sander and edge sander, applying stain (optional), and then two to three coats of polyurethane or hardwax oil — a multi-day process with significant dust and fumes.

For most DIY installations, pre-finished engineered hardwood is the practical choice. It avoids the complexity of sanding and finishing while delivering excellent results.

Final Thoughts

Hardwood floor installation is one of those projects where the preparation work — acclimation, subfloor flattening, moisture testing — determines most of the outcome. Spend the time getting those steps right, and the installation itself will be straightforward. Rushed subfloor prep is the cause of almost every hardwood floor failure: cupped boards, squeaks, loose planks, and buckled sections all trace back to moisture problems or subfloor issues that could have been caught before the first plank went down.

Take your time, use the right tools for your installation method, and you will have a floor that serves your home beautifully for decades.