One of the key challenges when installing hardwood floors correctly is ensuring the right moisture conditions. Proper moisture management not only ensures a beautiful, long-lasting floor but also guarantees customer satisfaction and protects the installer’s and floor manufacturer’s reputation. And if moisture problems arise, you, as the installer, want to ensure that the problems cannot be traced back to mistakes you made during the installation.
It is true that installing a floor correctly involves more than just the moisture content of the floor planks. However, if the wood moisture content of the floor planks and the moisture conditions around the floor are not right, even the best machinery and best installation techniques cannot prevent floor covering failures. This is especially true when the floor “starts working on its own.”
Conditions Required for Installing Hardwood Floors Correctly
Regardless of where a floor is installed— whether in a home, office, library, or gymnasium— the floor is always part of the building envelope. Moisture exchanges occur between building components and ambient relative humidity conditions until an equilibrium is reached.
The installer should only start his job, when stable conditions between moisture, relative humidity and temperature are guaranteed – from the beginning of the installation and continuing after the building is occupied and the floor is in use.
Thinking backwards, floors should only be installed if the same conditions exist as if the building were already occupied and the floor was already in use.
It is well known that for a successful hardwood floor installation concrete slabs must be dry, windows must be in place, and the HVAC system should function properly. But, this can pose a real challenge for the floor installer who wants to install the hardwood floors correctly under the right conditions. When on the other hand, architects, contractors, and home owners often want the work completed as soon as possible, even if the building is not ready yet to receive the flooring material, let alone have the floor installed.
Measurements Necessary to Determine Stable Conditions when Installing Hardwood Floors
- Ambient conditions
- Moisture content of floor planks
- Subfloor moisture
- Moisture in existing or new concrete slabs
- Moisture in other building components such as ceilings, walls,…
Pin and Pinless meters as well as Thermo-Hygrometers are essential tools for floor installers
Moisture meters such as the Ligno-VersaTec or the Ligno-DuoTec BW from Lignomat can measure all of the parameters needed to determine if the conditions are right for installing a hardwood floor correctly. However, it is not enough to just obtain the moisture and humidity measurements, you also need to know the acceptable range for each of these parameters? Is a moisture content of 6% acceptable? Is a relative humidity of 55% acceptable?
Generally accepted values for wood flooring are 6-9%, which occurs at a humidity of 30% to 50% and an ambient temperature of 60°F to 80°F. Also recommended by the NWFA.
Moisture Content of Floor Planks & Ambient Conditions
With HVAC system:
For comfortable and healthy relative humidity and temperature, HVAC systems typically maintain relative humidity between 30-50% and temperatures around 72°F. Under these conditions, a wood floor will acclimate to between 6% to 9% moisture content. The best way to avoid moisture problems is making sure that the floor has a moisture content between 6% and 9% when installed.
Without HVAC: The 6-9% rule does not apply to all areas of the US. There is a difference, if you install floors at the Florida coast or in the Colorado’s high desert. Additionally, seasonal changes can affect moisture content. The NWFA has published a Moisture Map for North America that shows moisture content variations by region and lists the expected ranges for different seasons.
The first task is making sure that the relative humidity and temperature are at occupancy conditions even a few days before the wood floor is delivered. Ambient conditions are measured with thermo-hygrometer. An instrument every floor installer should use.
EMC Chart
Next, consult the EMC chart to find the corresponding stable wood moisture content for the measured relative humidity. Acclimation is necessary when the actually measured moisture content is different from the listed EMC value for the relative humidity/ambient temperature.
For example:
- At 25% relative humidity and 70°F, the stable moisture content (EMC) is 5.5%
- At 55% relative humidity and 70°F, the stable moisture content (EMC) is 10%
- At 40% relative humidity and 70°F, the stable moisture content EMC is 7.7%
The Moisture Calculator lists the desirable relative humidity and ambient temperature for each wood moisture level (and vice versa).
It is a fact, every floor installer should measure wood moisture and relative humidity. The values need to be close to values listed in the EMC chart. The floor manufacturer’s manual may also offer specific recommendations for addressing situations when wood moisture and relative humidity fall outside the standard range.
Subfloor Moisture and Concrete Moisture Are also Important for Installing Hardwood Floors Correctly
Best practice is to keep the difference in moisture content between floor and subfloor as small as possible. Differences between floor and subfloor moisture are in general 2% or 4% depending on floor and floor installations. Installation guidelines often recommend vapor barriers to separate floor from subfloor to prevent moisture infiltration. Again, to be safe, follow the manufacturer’s installation manual.
Concrete Moisture
Concrete can hold a lot of moisture, especially if it has been poured only recently. Here again, a test will give you peace of mind and also avoid having a moisture problem disaster. Two tests are common practice: the Calcium-Chloride test and the in-situ RH test. Again, we refer the installer back to the manufacturer’s floor installation guide. → Comparison of Concrete Test Methods.
Occasionally, customers reach out to us with questions about how to measure moisture in concrete. They often ask, if they can use a pin or pinless meter to measure the moisture in concrete floors before installing a wood floor. Every time we advise them to refer to the floor manufacturer’s installation guide. → Summary of concrete moisture meters. → Summary: Concrete Moisture Meters.
It is worthwhile to follow the manufacturer’s installation guide. When moisture problems arise later, the finger pointing starts. Who is responsible? You want to be sure to have installed the floor correctly.
Moisture in Other Building Components such as Ceilings, Walls,…
If there is reason to believe, that access moisture is in any of structural components take moisture measurements. Measure close to the floor and up towards the ceiling, compare. If there is moisture intrusion through badly sealed walls, that will affect the floor eventually.
Record Keeping
That brings us to the first and last very important task for every installation. It is the floor installers job to record all measurements he takes throughout the installation process. A complete record includes name of instrument, species settings, date, time and measured values. Not to forget, documenting the final moisture of the floor and relative humidity at the time the customer signs off on the job.
It may also be helpful to issue a warning to the owners that humidity conditions should not deviate from the recommended 30%-50%. If ambient conditions change for an extended period of time, the moisture content of the floor will change too. This can lead to moisture-related issues, especially if only one side of the floor planks picks up or loses moisture. A cupped floor is no longer a beautiful floor!