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  • Facing Cupping and Warping in Douglas Fir

    Posted on April 13, 2011 by nell

    Douglas-fir gets along with just about everybody. Builders rely on Douglas fir lumber for its stability and performance. Homeowners love its warm glow and natural charm. Mother nature respects it for standing its ground. The Douglas-fir is a popular tree because it produces a super likeable product. But, as much as we boast about this treasured tree, we also know that the Douglas fir isn’t fail safe. No wood is. And, we’re okay with that. We want you to be too. So, bear with us as we confront the sometimes disagreeable side of Douglas fir: cupping and warping.

    What is it?

    Both cupping and warping are a distortion of wood. The difference, however, is in the type distortion. Cupping happens when the sides of the wood curve up or down. In this case, you’re left with wood that cups from side to side, or its width. Warping, on the other hand, is when the board bends from end to end and causing its length to bow.

    What causes it?

    Cupping is caused by a moisture imbalance which is common in wet humid environment like the Northwest. In other words, the moisture makes the wood expand. When wood is exposed to water it compresses and leaves it uneven over time. Basically, the wood is wetter in the center than on its edges.

    Warping is also caused from a moisture imbalance but usually happens when the wood is no longer attached to its structure. In other words, it’s no longer tied down, under the influence of H2O, and free to do whatever it wants.

    Cupping and warping happens more often on wide plank flooring. Basically, there’s more space and opportunity for the wood to move across a wide plank. With Douglas fir, or any wood flooring, the wider the plank, the less stable the wood.

    How to detect it?

    It’s not a pretty picture, but let’s say you’ve got a Douglas fir floor which has developed an unpleasant “smile” over time that catches your toes as you walk around the house. Is it intentional? Well, sort of. The floor has a moisture imbalance, and the wood just isn’t all there; it’s wetter at the bottom than on the top. Water somehow found its way through to its grain. Is it too late? Well, let’s take some steps to find out.

    Step 1 – Find the moisture source. It could be a leak from behind the bathroom sink. Or, if outside, it could be rainwater runoff hitting the deck steps from a faulty gutter.

    Step 2 – Get rid of the moisture source. Tighten up that tiny water hose behind the pedestal sink or replace it all together. Or you’ll need to replace that faulty gutter and keep on it.

    Step 3 – Now it’s up to your flooring. Once the moisture is gone or controlled, the wood may dry up on its own and go back to being more or less flat. We’d like to add that Douglas fir is great at doing this – it’s a reactive wood species and does a great job adapting to its environment. Either way, an air fan can help speed up the drying time.

    When the wood’s moisture content is stabilized, either through moisture-testing or naturally flattening out, decide on your next step. You can leave the wood be, refinish it, or replace it. With any of the above make a conscious effort to keep an eye on it just in case that moisture creeps back.

    How to prevent it the first time around?

    Acclimate the wood prior to installation. It’s true that Douglas fir does a darn good job of retaining its shape and size which helps against cupping and warping. But, acclimatization is essential – it’s the number one step to ensuring your wood is in harmony with its new environment.

    There are two more things that play a role in how your wood performs. Consider these when selecting the type and grade of your Douglas fir to minimize the likelihood of warping and cupping:

    Opt for kiln-dried lumber. This process quickly removes excess moisture evenly from the wood in a controlled environment whereas air-dried lumber takes much longer to dry. Kiln-dried Douglas fir is your best bet to ensure optimal acclimatization prior to installation – its moisture content is stabilized during the process and so you’re left with a wood ready to install in your home after a week of acclimatization.

    Vertical grain Douglas fir is harder and more stable than mixed grain. Not many types of wood present the beautiful tight vertical grain Douglas fir does. Over time, the tight grain will perform better than the mixed grain, but either grain will last for 50-100 years depending on how well the floor is maintained. Items such as paneling are typically sold in a mixed grain as it does not have to take the wear and tear that flooring does.

    Last words

    1. Use a dehumidifier to control humidity levels in your home.
    2. Use minimal to no water to clean wood, especially flooring.
    3. Use a floor care kit with products recommended for your wood species.
    4. We’ve heard through the grapevine that adding water to a distorted board or bending it back by force reverses the damage. Don’t believe the hype. You’ll end up more frustrated than before.

    - Nicole Morales



    This post was posted in All Entries, Douglas Fir Flooring, Care & Maintenance and was tagged with Douglas fir flooring, douglas fir floors, cupping, warping, cupping floors, warping floors

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