The Glue Down Method of Installing Hardwood Flooring
Glue down is When using the glue-down method, hardwood adheres to the subfloor, or to a moisture barrier that is mounted directly on the subfloor, using a strong adhesive. Although some exceptions may exist, we recommend attaching only engineered hardwood products. The subfloor must be completely dry and level to ensure proper installation. There are several different types of adhesives on the market. A professional installer will use the type of adhesive that is specifically recommended for your wood flooring products.
How it works
There are numerous reasons why people opt for glue-down installations as their preferred fixing method. Whilst we’ll get to the pros and cons in a minute, let’s look at what glue-down floors entail.
As with all fixing methods, you’ll need to ensure your subfloor is completely level. Gluing is often used when laying over concrete or wood. A strong adhesive specifically made for wood flooring is required to ensure longevity and premium quality. The adhesive is then applied to the subfloor in small, workable sections. This is done to ensure the glue doesn’t dry prematurely. As with laying any wood floor, you need to ensure an appropriate expansion gap is left.
Glue-down floors, technically, are usable on all wood flooring types. However, it is mostly used on solid wood boards which do not have a click or tongue and groove system. Whilst it can be used on flooring with these systems, it’s often seen as less cost-effective due to the extra materials and time needed for installation.
If you are laying over concrete, it’s crucial to ensure there is no dampness within the subfloor. Even the smallest amount can lead to issues in the future. If you can’t be certain there’s no damp, you can use a liquid damp proof membrane (DPM) before you glue your flooring down. This adds a protective layer to prevent the moisture getting into the wood.
The Benefits and Drawbacks of Glue Down Flooring
Glue down hardwood flooring often sounds more like real solid hardwood flooring than floating floors do. Because of the way it is installed there isn’t a hollow sound when walking across the floor or a spongy feel, this is something that can be an issue with floating floors if they aren’t installed perfectly and with optimal conditions.
- Glue down hardwood flooring also doesn’t require a vapor barrier because the glue itself acts as the barrier. This can reduce the installation costs for this type of flooring a bit, though they are comparable to one another when you account for the cost of glue and increased labor costs.
- Glue down flooring also shifts a bit less, and it can be used in surfaces that aren’t quite as level as what is required with floating floors.
Even though glue down hardwood flooring types come with quite a few benefits, they also take much longer to install than floating floors do.
- They are more difficult to install and will come with higher labor costs if you have professionals put them in.
- These floors are more difficult to remove if you decide you want to replace them down the road, and you’ll be working much harder to take off the adhered boards than you would with a simple click and lock type of floating floor.
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.
Before you begin
Before the installation begins, it is important to perform a thorough job-site inspection. Ensure that the HVAC is operational and the hardwood product is completely acclimated to the temperature and humidity at which the room will be maintained when occupied. The floor will be glued directly to the sub-flooring using a hardwood flooring adhesive. With that said, one of the most important factors while dealing with glue down installation is going to be your subfloor.
Subfloor preparation is critical on all job-sites, but especially for glue down. Subfloor preparation can range from sanding, scraping, leveling, filling low spots or installing a whole new subfloor. A general guideline while leveling your subfloor would be not to allow more than 3/16” difference in height within a 10 feet diameter. When gluing over a concrete slab, it is important to take proper moisture readings. The concrete slab needs the proper moisture vapor protection underneath and proper drainage away from the building. Once your subfloor preparation is complete and your floor is level it is time to choose an adhesive.
All adhesives are not made the same. When choosing which adhesive is right for your project, consider how hardwood flooring glue is specifically made for hardwood. Hardwood is a natural product and will expand or contract with the change in humidity as it takes on moisture or loses moisture. The difference between hardwood flooring adhesives is that they are made to embrace natural characteristics of wood, which is why it is specially formulated to be more elastic than other adhesives. The elasticity in hardwood flooring glue ensures that the hardwood will have an ample amount of space to expand and contract without causing the glue to crack or separate. Improper floor preparation, using the wrong adhesive, or applying incorrect amounts are all common pitfalls of a failed flooring installation. Certain hardwood adhesives also contain elements which act as a moisture barrier and/or a sound reduction. Be sure to consider all of these traits when choosing which adhesive to use. Next, let’s move on to installation.
Once you have decided to use the glue down floor method, make sure that you leave a large enough expansion gap, depending on the hardwood product you chose, from the wall to allow the wood to contract and expand. The adhesive is spread on an area of the subfloor where the boards are going to be adhered to using a specialized trowel. While installing, be sure to do small areas at a time. Do not pre-spread the adhesive over the entire sub-floor as it will dry before you get to that area. Furthermore, periodically during the installation, lift a board after you have placed it to make certain you have full coverage of the adhesive to the back of the flooring product. This will help ensure your floor will remain bonded to the subfloor for years to come. Once your flooring is installed it is best to let it dry for 24 hours, during this time you should not walk on it. The amount of adhesive used is adjusted by the teeth size of your trowel and may be dependant on if you need vapor barrier properties.