Before embarking on the installation journey, meticulous pre-installation considerations are paramount. Assess the concrete subfloor thoroughly, checking for moisture content, flatness, and smoothness. Excessive moisture can adversely affect wood, leading to warping and other issues. Acclimating the solid wood flooring to the environment helps prevent future complications such as cupping. Choosing the right wood species during this phase is essential, considering factors like hardness, grain patterns, and color variations.

Subfloor Preparation

The drying time for a newly poured concrete floor can vary depending on several factors such as the type of concrete mix, ambient temperature, humidity levels, and thickness of the concrete slab.

Here’s a rough estimate of drying times based on thickness. For a 4-inch (10.16 cm) thick concrete slab, it may take anywhere from 28 to 56 days to fully cure. For a thinner 2-inch (5.08 cm) slab, it might take around 14 to 28 days.

Check the moisture content of the concrete using a moisture testing kit. Ensure it’s within the acceptable range for installing wood flooring. Clean the concrete thoroughly, removing any debris, dust, or grease. Fill any cracks or holes in the concrete with a suitable patching compound and allow it to dry completely.

Moisture Barrier

Lay down a moisture barrier over the concrete subfloor to prevent moisture from seeping into the wood. Overlap seams by at least 6 inches and tape them securely.

Here are two common methods for installing solid wood flooring over concrete.

In this method, the moisture barrier is laid directly on the concrete subfloor. The moisture barrier can be a plastic sheeting or a specialized moisture barrier underlayment designed for this purpose.

The moisture barrier helps prevent moisture vapor from penetrating the wood flooring, protecting it from potential damage. Once the moisture barrier is installed, the solid wood flooring is laid directly on top of it.

Another option is to install a subfloor over the concrete, with a moisture barrier placed between the concrete and the subfloor. The subfloor can be made of plywood or oriented strand board (OSB), which provides a stable surface for attaching the wood flooring.

The moisture barrier is placed directly on the concrete subfloor before installing the subfloor material. The solid wood flooring is then installed on top of the subfloor, providing an additional layer of protection against moisture.

Both methods can be effective in preventing moisture-related issues with solid wood flooring installed over concrete. The choice between the two methods may depend on factors such as the condition of the concrete subfloor, local building codes, and personal preference.

Acclimate the Wood Flooring

Bring the solid wood flooring into the installation space and let it acclimate for at least 48 hours. This allows the wood to adjust to the temperature and humidity of the room.

The room temperature should ideally be between 60°F (15.6°C) and 80°F (26.7°C) throughout the installation process and for several days afterward.

Avoid extreme temperature fluctuations during and after installation, as they can affect the stability and performance of the wood flooringThe humidity level in the room should ideally be between 30% and 50% relative humidity.

Maintaining consistent humidity levels helps prevent the wood from expanding or contracting excessively, which can lead to issues such as warping, cupping, or gaps between boards.

If the humidity level is too high, consider using a dehumidifier to reduce moisture in the air. Conversely, if the humidity level is too low, consider using a humidifier to add moisture to the air.

Plan the Layout

Determine the direction in which you want to lay the flooring. Typically, it’s best to lay it perpendicular to the floor joists for stability. This orientation provides better support for the flooring and helps minimize the risk of sagging or unevenness over time.

Measure and mark the starting point for the first row of flooring, ensuring it’s parallel to the longest wall in the room. Use a carpenter’s square to ensure that the starting line is perfectly perpendicular to the walls.

It’s essential to leave an expansion gap between the flooring and the walls to accommodate natural expansion and contraction of the wood. Typically, this gap is around 1/4 to 1/2 inch (0.6 to 1.3 cm)

Lay planks in advance

It’s highly recommended to lay out your planks in advance as part of the planning process before securing them in place. This practice, often referred to as a “dry fit,” involves laying out the planks in the desired pattern and orientation without actually attaching them to the subfloor.

By laying out the planks in advance, you can visually assess how the flooring will look once installed. Dry fitting the planks enables you to check for any fit or alignment issues before permanently installing them.

During the dry fit, you may discover potential problems or challenges that could arise during installation. Dry fitting allows you to plan for transitions between different flooring materials or areas of the room. By laying out the planks in advance, you can optimize the layout to minimize waste and maximize material usage.

Adhesive

When installing solid wood flooring over concrete, it’s essential to use a high-quality adhesive specifically designed for this purpose. One popular option is Bostik’s BEST Ultimate Adhesive, which is moisture-resistant and provides a strong bond between wood flooring and concrete substrates.

To apply the adhesive, ensure the concrete subfloor is clean and dry, then use a notched trowel to spread the adhesive evenly. Work in small sections, allowing the adhesive to become tacky before laying the wood flooring. Once installed, clean up any excess adhesive and allow it to cure fully before walking on the floor.

Install the First Row

Apply adhesive to the back of the first row of flooring using a notched trowel. Place spacers along the wall to maintain an expansion gap.

Press the first row of flooring firmly into place, ensuring it’s straight and aligned with your reference line. Use a tapping block and rubber mallet to gently tap the boards together if needed.

Continue Installation

Apply adhesive and install subsequent rows of flooring, staggering the end joints for stability. Use a circular saw or table saw to cut the last board in each row to fit, leaving an expansion gap along the walls.

After spreading the adhesive, you can install the rest of the wood flooring using the tongue and groove method. Apply the adhesive to the concrete subfloor in small sections, then press the tongue of each flooring plank firmly into the groove of the preceding plank.

Use a tapping block and rubber mallet to ensure a tight fit between the planks. Continue this process, working row by row, until the entire installation area is covered.

Secure the Flooring

Once the adhesive has dried according to the manufacturer’s instructions, it’s time to secure the wood flooring to the concrete subfloor. Using flooring nails or screws, place fasteners at regular intervals along each board, ensuring they penetrate both the wood and the concrete.

Be mindful of the manufacturer’s recommendations for spacing between fasteners and their placement. This additional securing ensures a sturdy and long-lasting installation.

Finish the Installation

Once all the flooring is installed and secured, remove the spacers. Choose a wood filler that matches the color of your wood flooring as closely as possible. Wood filler is used to fill in any small gaps, cracks, or imperfections in the wood flooring.

Apply the wood filler to the gaps or imperfections using a putty knife, pressing it firmly into the area to ensure it fills completely. Smooth the surface of the filler with the putty knife or a damp cloth.

Allow the wood filler to dry completely before sanding the area smooth. Once dry, sand the filled areas lightly with fine-grit sandpaper to blend them seamlessly with the surrounding wood.

Molding, such as baseboards or quarter round, is used to cover the expansion gap between the wood flooring and the walls or other fixed objects in the room.

Measure and cut the molding to fit the perimeter of the room, ensuring a snug fit against the walls. Use a miter saw to cut the molding at 45-degree angles for clean, tight corners.

Attach the molding to the walls using finishing nails or adhesive, making sure to leave a small gap between the bottom of the molding and the flooring to allow for expansion.

If using baseboards, you can either install them directly onto the walls or onto a separate base shoe molding for added aesthetic appeal.

Once the molding is installed, fill any nail holes with wood filler and touch up with paint or stain as needed to match the surrounding trim.