Hey there, time traveller!
This article was published 11/1/2013 (1425 days ago), so information in it may no longer be current.
QUESTION: Two years ago we had a lovely Tigerwood floor installed in our kitchen. Overall, we love it. We bought it from a dealer in Niverville. They were wonderful to deal with, except for the information we received after installation. At the end of the job we were told, almost as an afterthought, "the warranty is void if you fail to maintain the humidity between 35 and 55 per cent." Apparently if it gets too dry, the wood will shrink and form gaps, or if it gets too moist in summer, it will expand and buckle. That disappointed us somewhat, for had we known that earlier, we might have chosen an engineered product or something else entirely.
So we bought a humidifier, and in winter we carefully pay attention to humidity and turn the machine on whenever it drops to the mid-30s. Not a big deal, but a bit of a nuisance. In summer, we do the reverse. If humidity climbs into the 50 per cent range, we turn on the dehumidifier downstairs.
Are we being too fussy? Does such wood ever "season" enough to not need this extra attention? Our house, built in 1969, has other hardwood throughout the main floor and it never seemed to have had a problem when humidity dropped below 30 per cent before we added the Tigerwood.
-- Walter Kroeker
ANSWER: Unfortunately, some manufacturers of building products have unreasonable stipulations attached to their warranties, mainly to avoid honouring them. That is why I always advise my clients that warranties are not to be relied upon too heavily when making decisions about product purchases. There are many examples of this, from flooring to shingles, and yours is another case in point.
There is a lot of information, much of it without scientific basis, about the need to maintain certain conditions for many building materials installed in homes. Some of this information is gained from experiences from homeowners, installers, and manufacturers of various products and should be treated with respect. Other information, such as that you received about maintaining proper relative humidity (RH) in your home to keep your wood floor in good condition, is unreliable and likely thought up by some shrewd lawyer to protect their client when problems occur. In our climate, interior RH levels change with the weather and maintaining artificially high humidity for this purpose can cause other negative effects. Also, how can you prove that you did maintain these "proper" RH levels if a flooring problem develops? It appears that this may be an excuse for manufacturers to blame defects in their products on less-sophisticated homeowners.
As you have stated, older hardwood flooring in your home has been in place for over four decades and has not become damaged from the fluctuating RH in all that time. Why would newly installed hardwood have different needs? If the material is an exotic wood, like yours, it may have different properties than the traditional oak or maple originally installed in your home. Regardless, numerous types of hardwood are very commonly used for flooring because they are very durable and adapt to environmental changes as well or better than most building materials. If the type of wood is not suited to changes in RH common in our area, then it should not be installed in our homes.
The majority of problems that occur with wood flooring in homes is due to the material itself or the conditions around the time of installation. After cutting and milling, wood flooring has to be dried, often in huge kilns with tightly controlled heat and moisture, to reach a fairly low moisture content. This is critical to prevent further shrinkage if the wood were to excessively dry out after being nailed down in your home. If the wood is not properly seasoned, gaps opening between individual planks is a strong possibility. Conversely, if the hardwood has a proper moisture content but the inside of the home is too wet as the wood is being installed or afterwards, buckling can occur as it absorbs this ambient moisture. This is most common in newly built homes, as the RH can be excessively high from drying of recently installed materials. For this reason, any wood flooring product should be stored inside the building it is to be installed in for several days or weeks prior. This will allow the material to acclimatize to the current RH, preventing dramatic shrinkage or swelling after being nailed down. This critical step has been adopted by flooring contractors for decades due to their experience and is a very probable cause of floor issues if missed.
Maintaining an RH close to 50 per cent in the heating season in our climate can cause excessive damage to the home. This will cause excessive condensation on windows and possibly other areas such as foundations, which can lead to moisture damage and mould growth. An RH at the bottom end of the recommended range near 35 per cent, at normal room temperatures, may cause some sweating windows in cold weather but may be all right if good air circulation is promoted. If the RH drops below 30 per cent inside your home on very cold days, which is quite common, that should not create any undue problems for the home or flooring but may feel dry to the occupants. Adding artificial moisture to the house air to raise the RH above the recommended level just to benefit the hardwood flooring may cause the same mould and condensation issues in areas with poor air circulation or on outside walls or windows. In the summer months and in many areas near lakes or oceans, the RH inside a home can easily exceed 50 per cent. While air conditioning should lower this to acceptable levels, moderate days when windows are open and air circulation is good should have little effect on your flooring if the humidity rises.
Having heard the requirements you have stated from many homeowners, and reading similar recommendations on various websites, including those of hardwood manufacturer associations, I am still at a loss to see any real proof of the need for these measures. As you and millions of other homeowners with older houses have observed, properly seasoned and installed hardwood flooring adapts well to seasonal climatic conditions, and defects should not be blamed on the home or its occupants.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and president of the Canadian Association of Home & Property Inspectors-Manitoba (www.cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at www.trainedeye.ca