Proper wood floor acclimation has been a question in many home owners and contractors’ mind prior to installation. Since wood flooring projects are major investment, it is wise to understand the true meaning of acclimation. Under certain circumstances, to wrongly acclimate your wood floor can lead to installation issues. Such as to potentially cause buckling or gapping which the manufacturers’ warranty will not cover.
Even though most manufacturers give a guideline to acclimate their solid or engineered wood floor, proper acclimation should be about more than just the amount of time that you let flooring sit on the job-site. In fact, there are two important conditions that decide whether it is enough to simply follow the manufacture recommended time in order to have a successful installation. Wood floor moisture content (MC) and relative humidity (RH) in the surrounding environment are very important in this process. In this article we will cover the proper moisture content and relative humidity for wood flooring to acclimate.
In a perfect world, the hardwood flooring should be dried specifically for the climate it will be installed in. Since this task is unfeasible for most mills because of logistics and efficiency limitations, industry standards suggest 6 to 9% as a desirable MC range for wood floors newly out of the mill. In other words, it is a fairly safe MC range for hardwood flooring to perform in both drier and more humid regions.
“Wood flooring is a hygroscopic material subject to dimensional change as a result of variations in moisture, temperature and humidity within the surrounding environment. Wood flooring simply needs to reach moisture content level in equilibrium with the surrounding environment (EMC) in which it will be installed. Warranty coverage generally requires that jobsite conditions be maintained between 30% to 50% relative humidity and that those conditions must be maintained before, during and after installation for the life of the floor.”
–National Wood Flooring Association
So now we know what good range of MC and RH are. Next, lets examine some specific real world situations. Things are not always as perfect as we hope on many job sites, especially for new constructions. Certain conditions should be met before wood flooring is delivered to the job site.
Builder wants to meet deadline for an open house at the end of the month. A batch of wood floor is delivered to the home with proper 6 to 9 % MC inside a house with taping, mudding and painting on site. The manufacture recommends a minimum 1 week acclimation period prior to installation. 1 week later, the installer shows up to install the hardwood. 24 hours before the open house for potential home buyers, the builder notices large gaps in his hardwood floors.
You are acclimating your floor in the environment in which the RH is quite much higher than normal living condition. Therefore, instead of conditioning the moisture of the wood floor to the right environment, you are adding moisture to the wood flooring. This is a potential problem because the wood will slowly take on more moisture, and when the flooring eventually adjusts to normal living conditions it will shrink resulting in gapping or surface cracks.
Next, let us examine if we put in a high moisture wood floor into a house with ideal relative humidity of 40%. This time you receive a batch of hardwood floor with 11-13% MC for your house remodeling in Minnesota. You were told to acclimate the wood for a week before installation by the sales person at the retail store. The floor contractor installs your floor according to manufacturer’s guideline. Several months later, right in the middle of the winter, you start to notice gaps which can fit a half dollar coin between several planks within your hardwood.
Your one week was not enough to acclimate the hardwood floor from 11-13% MC to 6-9% MC you need in your Midwest home because your floor continues giving out moisture after the installation in those winter heating months. The floor shrinks and gaps show. If the same floor is delivered into a house in Florida, the outcome might be quite differently because the equilibrium moisture content will be between 11-13% MC.
Contrary to popular belief, wood floor acclimation has less to do with the amount of time but more to do with its MC being in equilibrium with the environment in which the floor is installed. Knowing the common pitfalls and how to avoid them is what separates the pros from the rest.