Image showing the glue down installation of a hardwood flooring

How to Install Glue Down Hardwood Flooring

Written by: BuildDirect



Time to read 8 min

There are multiple methods of installing hardwood. Your budget, pre-existing flooring and sub-floor can all play into the decision of which method to choose. If you have decided that glue down hardwood flooring is right for your home, we’ve provided everything you need to know before and during the installation process.

What to Know Before You Begin

Installer/Owner Responsibility

Hardwood flooring is a beautiful product of nature with inherent variations in appearance. It is important to note that prior to installation, the installer and/or owner of assumes responsibility for carefully inspect the flooring as to grade, manufacture, color and finish. Typically, the owner’s responsibility also applies during his/her absence from the installation site. If a flooring board is not acceptable, do not install it and contact the seller immediately. Once a board has been nailed or glued down, it is deemed accepted by the installer and/or owner . Manufacturers generally deny any responsibility for judgment errors and/or for poor installation quality of their products.

Tools and Accessories Needed for Glue Down Hardwood Flooring Installation

  • · Industry Standard Adhesive
  • · Trowel
  • · Concrete nails (to secure holding block)
  • · Blue adhesive painters tape

Temperature and Humidity

Hardwood is a living material which reacts to changes of relative humidity. It absorbs or releases humidity according to seasons. To allow for proper acclimation, the heating/air-condition system must be operational for least 14 days prior to installation and thereafter at a temperature of 65°F- 75°F to reach desired humidity level. The relative humidity level at home is best kept controlled between 35% – 55% at all times prior, during and subsequent to installation.

In summer, when humidity is high, hardwood absorbs the humidity in the air and expands. The expansion causes the strips/planks of wood to push against each other. This is called cupping. YOu can minimized these variations with proper ventilation and dehumidifying. On the other hand, in winter, the relative humidity level at home is much lower due to the usage of heating system. The wood releases its own humidity and the strips/planks contract or shrink. To minimize extreme shrinkage effects it is best to use a humidifier in these conditions.

Storage and Handling

It is best to store hardwood flooring in a controlled environment within the above mentioned temperature and humidity. In order to meet minimum installation requirements for moisture content, material delivery should occur 72 hours prior to installation, or as long as necessary for the hardwood flooring to acclimate. Acclimation within a closed carton may not be adequate due to lack of air movement. Handle and unload with care. Store the flooring in a dry place and provide air space under cartons.

Do not unload or transport flooring during wet conditions (i.e. rain, sleet or snow) because the wood will absorb moisture, which will cause it to swell. The swelling of the wood will cause problems, because eventually the wood will shrink back to its normal moisture content, and the resultant shrinkage may produce gaps in the finished flooring.

Considerations for New Homes

If installing glue down hardwood flooring in a new house, completely close the building in with all outside doors and windows in place. All “wet” work (such as concrete, masonry, framing members, drywall, paint, etc.) should be thoroughly dry. The wall coverings and painting should be completed before the installation of the hardwood flooring.

In order to avoid damage caused by moisture, make sure basements and under-floor crawl space are dry and well ventilated. Plastering and concrete work must be completely dry with minimum of 90 days curing time. Freshly poured concrete slabs emit many gallons of moisture as water vapor. No concrete should be poured after the flooring is installed.

Exterior grading should be complete with surface drainage offering a minimum drop of 3″ in 10′ to direct flow of water away from the structure. All gutters and downspouts should be in place.

Job Site Requirements

Solid hardwood flooring only can be installed on or above ground level with a plywood subfloor. Engineered flooring can be installed above grade, at grade and below grade level. Do not install hardwood flooring in bathrooms. Check with the manufacturer’s instructions to determine if your hardwood floor can be installed over an in-floor radiant heat system.

Crawl spaces must be a minimum of 24″ from the ground to underside of joists. A ground cover of 6-8 mil polyethylene sheeting is essential as a vapor barrier with joints lapped six inches and taped. The crawl space should have perimeter venting equal to a minimum of 1.5% of the crawl space square footage. These vents should be properly located to foster cross ventilation. Where necessary, local regulations must be met. Crawl spaces must be dry and well ventilated. Use a moisture meter to check the plywood (subfloor) moisture content. Delay the installation if the moisture content of the plywood (sub-floor) exceeds 12%.

Engineered flooring can be installed over a dry concrete subfloor. In order to test the moisture level of the concrete subfloor, tape 18″ x 18″ clear plastic sheeting to the floor in two spots, sealing all sides with moisture resistant tape. Leave in place for 48 hours and then remove. If after removing there is no condensation on the underside of the plastic sheeting, the concrete slab can be considered dry enough to install the engineered flooring. If there is moisture on the plastic sheeting, there is a problem and the flooring cannot be installed.

A professionally installed moisture barrier would be required. Using the moisture meter, check the moisture content of the hardwood flooring to ensure that it is within the acceptable moisture range of 6% to 9%. The installer and/or owner has full responsibility for moisture testing the wood or concrete subfloor and the hardwood flooring prior to installation.

Sub-Floor Surfaces and Conditions

  • · Preferred ¾” CDX grade plywood with minimum of 5/8″ CDX grade plywood over joists subfloor.
  • · Existing wood boards over joists subfloor and
  • · Dry Concrete sub-floor ( only for Engineered Hardwood Floors )

Note:  Particle board or other similar type products are not suitable subfloors.

Sub-flooring must be clean, smooth and free of wax, paint, oil, sealers, adhesives, curing agents and other debris. Subflooring must also be straight, flat and leveled. Sand high areas or joints to achieve this. Flatten low spots with layers of builders felt, plywood or shims (not leveling compounds). Subflooring must be structurally sound. Nail or screw any loose areas that squeak. Replace any damaged, swollen or delaminated subflooring. Sub-flooring must be completely dry and meet with moisture content requirements.

Sub-floor preparation is a very critical step prior to the installation of your new floor. The hardwood and bamboo floor is only as good as what is underneath it. Laminated rosin paper or construction paper acts as a moisture retarder and may be used to reduce movement caused by changes in subfloor moisture. Therefore it may reduce cupping and warping. It may also reduce sound transfer, and to prevent noise caused by minor irregularities and debris.

General Instructions Prior to Installation

  • · It is recommended that the flooring be installed at a 90 degree angle to the joists for wood subfloors. An additional 5% flooring must be added to the actual square footage needed for cutting and grading allowance.
  • · Plan out the installation determining an appropriate color match of boards. Floor should be installed from several cartons at the same time to ensure good color and shade mixture.
  • · Remove any existing base molding, other moldings, door sills and old floor covering where applicable. Using a hand saw, undercut the bottom of door frames ¾” to slide hardwood board beneath.
  • · Do not use flooring pieces with obvious defects. It is the installer’s/owner’s responsibility to ensure that the conditions of the flooring are acceptable prior to installation. The manufacturer declines any responsibility for flooring which is installed with obvious defects and/or flooring which is installed under improper jobsite conditions.

Glue Down Hardwood Installation Guidelines (For Engineered Floors Only)

Ensure that all the above sub-floor conditions and general instructions have been met.

Determine a starting point. When possible, always begin the layout from the straightest wall, which usually tends to be an outside wall. Measure out from this wall at each end the width of two boards (including the tongue) and then add an additional 3/4″ for expansion. At these measured locations, mark a chalk line parallel to the starting wall. The chalk line is the starting line for the placement of the floor. Note: The working area between the starting wall and the chalk line will be the last floor area installed. We recommend nailing down a holding block or securing it between the chalk line and the outside wall to secure the first row of floor and prevent movement.

Ensure that the room is well ventilated.

Apply the adhesive to the sub-floor area in accordance with all manufacturer’s instructions to cover the width of approximately the first two rows of planks. Spread the adhesive holding the trowel at a 45 degree angle to the sub-floor, in accordance with the manufacturer’s recommended spread rate. As a general rule, limit the application of adhesive to the subfloor to the area which can be covered in 30 minutes so as to prevent drying out of the adhesive. However, the drying time will vary depending on job site conditions.

Use the longest, straightest boards for the first two rows.

Leave a ¾” gap alongside both the left wall and right walls which are perpendicular to the starting line to serve as expansion gaps Install the first row of planks along the chalk line/holding block with the tongue side propped against the holding block, and press the board down for adhesion to the subfloor. Select a long board as the last board of the row. You can use the cut portion of the last board as the starting board of the next row to minimize waste.

Ensure that the first board used for the second row is at least 6″ longer or shorter than that of the first row.

This staggers the floor joints to achieve a more favorable appearance. Insert the tongue end of the second row board into the board groove of the first row board and slide securely into place. Press board down for adhesion to subfloor.

Follow the same procedure for the installation of subsequent rows.

Again, be careful to stagger the end joints by at least 6″. Do not walk on the freshly laid floor. Apply blue adhesive painters tape perpendicularly to the seam of adjoining rows to prevent the rows from spreading apart. Any adhesive which gets on the surface of the flooring needs to be removed as soon as possible by using damp, clean towels and followed by immediately drying the cleaned surface. Replace the towels often to ensure effective cleaning.

When installing the row adjacent to the end wall leave an expansion space of approximately ¾”.

After installing the end wall row, go back to the area between the starting wall and the chalk line. Remove the holding block and proceed to glue down the first two rows between the chalk line and the starting wall. Remember, your measurement from the starting wall already should have provided for a ¾” expansion space. After the installation is complete, wait 24 hours before walking on the floor and moving any furniture or objects onto the floor.

Complete the Installation

  • · At completion of the installation, vacuum thoroughly and clean the floor with proper wood flooring cleaner on a soft, cloth mop. Then wipe the surface clean to remove loose dirt or soil.
  • · Reinstall all base and/or quarter round moldings. Nail the moldings into the wall, not the floor.
  • · Install any transition pieces, such as reducers, T-moldings and stair nosing.
  • · Keep several spare boards from the installation in the event of future repairs.