This is part of a series on wood flooring in the winter. Read part one here. Bryan is the regional manager for our Northern store locations and has been with The Master’s Craft for 10 years.
Last week I wrote about how the relative humidity of indoor air is affected by temperature, and that it is feasible for RH levels to drop to as low as 7% during the winter. I had this thought, but if you have a home at 7% RH, would it be drier than the Sahara desert? I was curious and did a little googling and came across this. It’s legit: if you don’t humidify your home in the winter, you may be living in a more extreme environment than the Sahara desert. Tell your husband, tell your wife, your kids, and even the dog. You can also read my previous post on why the humidity level drops so precipitously during cold months.
Let’s get back to the Sahara. In addition to being one of the most inhospitable environments on the planet, Sahara desert humidity levels in your home will likely destroy your wood floors. Why is that and why don’t you see many trees in the Sahara?
Well, wood is basically a sponge. When the environment around it is wet, wood soaks up that moisture. When the environment around it is dry, wood dries out. In addition to simply gaining or losing moisture, wood also expands or contracts based on this change in moisture. Repeat after me, when it gets wet, it grows, when it dries, it shrinks.
You can predict what direction the floor will grow by its growth rings. Depending on how the flooring was cut from the log, the floor will expand in the direction of the growth rings. Here’s a link for you to investigate this further if you’d like. I highly recommend it.
In short, when your floor gets wet, it’ll get wider. When you dry it out, it will get more narrow. And when you get it Sahara desert dry? Well, things start hitting the fan, including the fasteners.
What happens when a floor gets really dry
Here’s a rundown of what will happen when your floor is Sahara dry:
- The floor shrinks (gets more narrow).
- Suddenly there are openings between your boards (gaps).
- When the floors get more narrow and cause gaps they squeak. This is usually a case of fastener stress. The floor was likely nailed down and when you have a cold winter season, the floors will shrink and the staples or nails holding it down get pulled. When you step back on that board, you push the nail back in… squeak!
- The floors can also squeak, pop and crackle! Thank you dry cupping!
A quick primer on dry cupping
Your floor was once a round tree that was cut down into rectangles and dried, then installed in your home. When a wood product is significantly changed from its acclimated structure, it will tend to go back to its original state.
When the floor is significantly wet or dried from its acclimated state, it will bow, sort of like a sheet of paper or book that has gotten wet. This is called dry cupping. The dry cupping can be significant or very subtle, but in either scenario, the raised edges of the floor will have flex and allow movement which will be visually bothersome and cause squeaks, pops and crackles. Okay, moving on…
Any floor can fail when put in extreme conditions
The reality is that wood needs a consistent environment to maintain its desired physical characteristics. If the conditions of the home that the floor is installed in are outside the recommended range of the manufacturer, failure can happen. Your wood floor is likely one of two types of construction: solid or engineered. Solid is pretty self-explanatory but let’s focus on engineered. It can be a little more difficult to understand but in one sentence: engineered wood floors are real wood veneer glued to plywood.
Engineered wood floors allow recycled and less expensive product to be used in the base layer of the wood floor, while using less of the “good stuff” up top. It also can be more stable. The alternating pieces of plywood resist each other when dried or wet, and the floor will expand or contract less with changes in moisture content. This is all well and good until you put it in conditions resembling the Sahara desert. The drying forces are so great that the floor may tear apart. It is not that the glue failed between the plys, the wood fibers actually start to tear apart.
There you have it! Things can get bad when your floor moisture goes below 30-35%. This winter, be kind to your floor and don’t give it the Sahara treatment.