Hardwood Installation Best Practices
There are a few key factors that play a large role in a successful hardwood flooring installation. Installation methods will vary depending on the species, width, thickness, and construction of the flooring as well as the subfloor type. Following manufacturers’ recommendations is always a good start. Industry installation guidelines are provided by the National Wood Flooring Association (NWFA) and have become common practice by a large number of hardwood flooring contractors.
Knowing the intended use of a space, as well as the overall look desired, are both very important in the planning stage of a hardwood flooring project. Categorizing a space as light, moderate, or heavy traffic for residential or commercial use will help dictate what type of flooring material will be used. For instance, if the space is a retail shop with lots of daily foot traffic, a softer species like pine would not be suitable. This is where the Janka hardness scale comes into play. This can help decide the proper flooring based upon the traffic it will be subjected to. Wood is a natural product, so this is a big factor in the success of a floor.
The overall look is equally important to the overall success of a flooring project. Choosing a species like white oak, for example, will give you a blank canvas to work with as far as colors, due to the light natural color. White oak is one of the most popular species for colors. When using a darker species, like American walnut, you will be limited in your color pallet, as you are starting with a darker wood and going lighter will be more difficult. Proper selection of a suitable wood species for the space will dictate the installation methods used.
Moisture is the number one cause of failures in the flooring industry. Controlling moisture from below the flooring, as well as above, is crucial for a long-lasting, successful floor. Not only is keeping moisture in balance good for wood floors, it turns out it’s actually very good for the overall well-being of humans. Bacteria and viruses thrive in extremes – low and high moisture and temperatures. Humidification in the winter and de-humidification in the summer becomes more important to stay within acceptable ranges. Getting the space ready for hardwood flooring is just as important as getting the wood ready for the space. These two are inseparable.
Moisture testing is the only way to know when a hardwood floor is ready to be installed. Taking moisture readings of subfloors, flooring material and conditions inside the space will dictate the timeframe for proper acclimation. There is no set amount of time for acclimation. The NWFA has guidelines for flooring and subfloors, on acceptable moisture content ranges depending on what part of the country you live in. This is very valuable information when planning a project or writing a specification. Extra time allotted for the installation of hardwood floors should be integrated into every project.
Moisture is also present in the subfloor, wood or concrete. Moisture retarders and moisture barriers are used in the flooring industry to combat excessive moisture in their respective subfloor applications. Moisture testing should be considered with every project or specification and will indicate if such products are needed. Relative Humidity (RH) and Calcium Chloride (CaCl) are the two most widely accepted methods for measuring substrate moisture levels. Allocating the proper time and budget necessary will ensure a successful installation.
Vapor retarders are used on wooden subfloors (plywood or OSB) as well as gypsum based underlayments, to slow down the transmission of water vapor to the flooring from the subfloor. Wooden substrates need to breathe, otherwise, mold, mildew and rot can develop. There are various products on the market to help with this. Again, following manufacturers’ guidelines is always recommended.
Vapor barriers are used on concrete subfloors with high moisture readings. Concrete subfloor prep is critical to the success or failure of these vapor barriers. Different technologies exist, ranging from 2-part epoxy systems to trowel-on membranes to roll-on penetrating barriers. Adhesives have even advanced enough to have higher moisture resistant properties. It is always a good idea to contact the manufacturer’s representative prior to starting a project or writing a specification. This will give you the information necessary to choose the proper products and installation methods.
Solid wood flooring is generally installed over wooden subfloors using a nail down method or a glue and nail assist for wider planks. Specifying a glue that’s easy to spread, has zero VOC’s and doesn’t chemically damage a pre-finished hardwood floor surface is recommended. These practices make the installation process easier and in turn, saves time and money. Solid floors can also be installed over concrete, just keep in mind that the milling of a solid hardwood for a glue-only installation needs to have smaller tolerances in variation, so this usually means a higher price for that product. Also, solid wood floors are typically only used on and above grade.
This is where engineered flooring has an advantage. It can be installed below, on, and above grade and near wet areas (ocean, lake, river-front) since it is a more dimensionally stable product. Engineered wood flooring also comes in more thickness variations than solid flooring, so it can be used more widely when height restrictions are considered.
In most cases, timeframe and budget will ultimately dictate what type of hardwood flooring is used for an installation. A factory pre-finished floor typically has a higher starting price for the material, especially the higher quality products. Customers can also move in faster since the floors are usually ready for partial or full use the next day. You are limited to the colors and finishes that the manufacturer has chosen, and quality control can be difficult with some of the newer color trends.
An unfinished solid product has a lower material cost, and generally a lower installation cost. The largest variable in the cost of unfinished flooring is the actual finishing process. The sanding and processing of the unfinished floor plays a significant role in the quality of the installation and can vary depending on the finish desired. Regarding the finish, there are many options in today’s market ranging from custom penetrating oils to water-based and polyurethane coatings. Each finishing method requires a level of skillset and the installer chosen should be properly trained for the type of finish being applied. One of the great appeals of an unfinished floor is that it gives the designer, architect or homeowner a blank canvas with endless color options. They can be fully customized to any taste or environment. Engineered unfinished flooring is also available and has similar properties to the solid product, but with the added availability of different thicknesses as well as providing a more dimensionally stable flooring product, especially in extreme climate changes.
These are just a few key points to keep in mind when planning or specifying a hardwood floor installation. The use of the space to choose an appropriate species and construction of a product is a critical stepping stone. This choice dictates future installation steps as well as the overall look and performance of the products. Following manufacturers’ and industry guidelines is always recommended and preferred. Many manufacturer representatives will do in-house training and seminars on these topics and how their products can help streamline the installation process. Specifying enough time for the installation is always appreciated and the biggest key for a successful hardwood flooring installation is controlling moisture. With moisture under control, hardwood floors can be installed practically anywhere. When properly installed and maintained, a hardwood floor can last for generations.