Your new hardwood flooring has arrived, and you’re understandably eager to get it installed because it’s the last touch in your home construction or renovation project. You can almost taste the satisfaction of completion after months of gradual progress.
But hold on a second. What was that advice you got about acclimatising your wood floor before installing it? What does acclimatising entail, and will skipping it be a mistake?
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Acclimation is the process of adjusting (conditioning) the moisture content of wood flooring to the environment in which it is expected to perform, this is the room it will be installed in. Wood is hygroscopic, which means it expands and contracts when it comes into contact with moisture.
Prior to installation, the flooring should ideally be brought into balance with the typical living conditions of the space, this means it is given time to get used to the room’s natural temperature and moisture levels. Without such conditioning, the beautiful wood floor you put down today could turn into a disaster when the next season arrives, with the potential for dimensional distortion, excessive shrinkage or expansion, and structural damage.
If you don’t allow your flooring to acclimatise, it may warp, crack, buckle, or split. It’s also possible that you’ll be left with unsightly gaps. This is because floors naturally expand and contract. This is even more true for real wood flooring, as they are natural products, which is why their acclimatisation times are longer. The temperature and humidity levels in each room are different. Because your flooring was most likely stored in a big warehouse, the atmosphere in which it will be installed is very different. If you immediately lay your flooring without letting it acclimatise, it will expand or contract due to the sudden change in environment. This is where damage most occurs.
Moisture content is a function of both the relative humidity and temperature of the surrounding air. The wood used in the engineered wood flooring industry is generally dried to a moisture content between 6 and 9 percent using a combination of air and kiln drying. In a stable environment in which the wood is neither gaining nor losing moisture, equilibrium moisture content has been reached. In a non-stable environment with longer-term fluctuations in humidity and temperature, the impact on the flooring can be dramatic.
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The process of achieving equilibrium moisture content is unfortunately fraught with confusion, mixed messages, and even misinformation. The worst offender is the assumption that flooring should simply be left in the setting where it will be installed for a certain amount of time. In fact, acclimation is dependent not on time, but on the environment in which the flooring will be installed. In some cases, time will be useful; in other cases, it will be unnecessary and even detrimental.
Far more critical is the moisture content of the flooring in relation to the moisture content of the surroundings, best measured by testing with a properly calibrated wood moisture meter both the plank flooring and the subfloor on which the flooring will be laid. Acclimated wood flooring would not have more than a two-percent moisture content difference from the subfloor. This will typically take 3-7 days, but if you live in an area with high or low levels of moisture you may have to wait a little bit longer.
Additionally, your flooring installer should be thinking more holistically about the specific location in which the flooring will be installed.
These factors will influence the speed with which acclimitisation occurs, and provide insight into how your engineered wood flooring might behave with climate changes in the future.
For example, if you live in a place where the winters are cold and dry, while summers are warm and humid, it will prompt the potential for significant seasonal expansion and contraction with your hardwood floors. The acclimatisation period in a home heated by dry wood heat will likely be lengthy in the winter, but in the summer, with no air conditioning to control temperature and humidity, acclimatisation may be almost instantaneous because the moisture content of the hardwood flooring and subfloor may already be within 2% of one another.
Before Delivery
Establishing consistent current living conditions at the project site is the critical starting point as the wood flooring needs to be received in the finished environment to allow time for it to adjust to the ambient temperature.. This means that air conditioning or heating systems have been running for at a constant temperature for at least five days, creating an ideal environment of 19-24 C degrees at 35-50% relative humidity, with certain geographic exceptions.
If air conditioning is not yet (or will not be) installed, fans and dehumidifiers should be utilized to mimic normal living conditions. If the space is being renovated and has been recently re-plastered or painted it is important to ensure that all work is completed and dry. If it is a new construction site, the building should be completely enclosed with all windows and doors installed, and all wet construction elements – such as plastering or concrete – should be completed and dry.
In natural settings humidity, moisture levels and temperatures change according to the season and it is important to know the long term relative humidity for the area. This will determine whether your engineered timber flooring will absorb moisture from the air and swell or whether it will lose moisture and shrink.
After Delivery
The hardwood flooring planks will arrive with approximately 7% moisture content. Test the moisture content of the subfloor at multiple locations (recommended 40 tests per 300m) to get a baseline. If the subfloor measures 12% moisture content, you need to bring the flooring planks to within 2% of that. The room temperature and humidity levels need to be stable and the temperature of the room shouldn’t be lower than 18C degrees.
When your flooring arrives onsite, bring it into the pre-prepared room. It may be less convenient than storing it in a garage but this is an absolute no no. Storing in an environment of fluctuating temperature will cause the timber to move unnecessarily.
For engineered hardwood flooring, some people mistakenly believe that the product’s greater structural stability eliminates the need for acclimatisation. Though it is true that engineered products do not swell and shrink with environmental fluctuations as much as solid hardwoods, they do still have the capacity to expand and contract. As such, they also should be acclimatised to the surrounding environment, as judged by comparative moisture reading between the flooring and the sub-floor, even if the subfloor is concrete. Engineered floors are particularly susceptible in extremely dry environments, so that climatic concern should be taken into account.
To acclimatise effectively, the planks should be unpacked from their boxes and stacked to allow air circulation on all sides. Some packs can be very heavy, so ensure when stacking that they are stable and not too high. Leaning boards against the wall, or standing on their edge might seem like a good idea to save some space but propping it up will likely cause bowing. We strongly advise that all flooring is laid flat.
If your floor was delivered on a rainy day and has absorbed moisture, allow extra time for acclimatisation before continuing with the installation process.
If the moisture content of the subfloor and new planks are within 2% right off the bat, we still recommend 48 hours for the floor to get comfortable in its new environment.
Fitting over underfloor heating
Just a note on fitting over under floor heating. Firstly, if you have under-floor heating set within a new screed, ensure the underfloor heating is turned on (according to the suppliers instructions) before any flooring is fitted or left to acclimatise. Run the heating for at least a week at a normal running temperature prior to receiving the boards. Reduce to a minimum a week before the flooring arrives. (A temperature of between 18-20 C of the water inside the pipes of the underfloor heating needs to be achieved). Maintain this temperature whilst the flooring and finishing is being completed. On completion the heating can be turned up by a maximum of 1-2 C a day each day until the desired temperature has been achieved, but not more than 27 C.
If you’re not experienced with the process, hire a trusted professional installer, and talk to them about the acclimatisation process. Engineered wood flooring is a big investment, and you’ve only got one shot to get it right.
Elevate your interior with VidaSpace. Contact us and one of our team of trained interior designers will be able to guide you through the process.
