Log Checks – to Seal or Not to Seal?

Every homeowner has found checks in the logs at one time or another. Checks are those longitudinal splits that appear as logs lose their moisture. While you may like or dislike checks, they are a part of the character of wood. Some species of wood are more susceptible to checking than others. This susceptibility comes from the different rate at which wood shrinks in its own geometry. Because wood dries out from the surface, the wood at the surface shrinks faster than the wood further down in the core.

Additionally, researchers have found that wood shrinks faster in the tangent direction (around the perimeter) than it does radial direction (toward the center). The ratio between these shrinkage rates tells you which species of wood are more likely to check. The greater the ration the more the wood is likely to check as the logs dry.

Late summer or early fall is the best time to seal up your checks.

Should you always seal up checks?

The answer is partly a matter of practicality. If your checks are protected from any source of water or the opening is downward and they do not allow air drafts to enter the interior of the house, then it is really not necessary to seal them up. However, if the checks face upward to that they can collect blown rainwater, then weather conditions can introduce water into the heart of your logs – a very undesirable condition that can result in wood rot in the log.

What should you use to seal up checks and how do you do it?

Because seasonal weather variation cause checks to open and close slightly, you must use material that tolerates the movement. By the way, this movement is reduced when you have a good water-repellent and flexible coating on your logs such as Lifeline stain and Advance topcoat.

When you are sealing checks up, do not fill the check completely up with the sealant. On wider checks you should able to push some backer rod into the check so that you have about ¼ inch depth remaining for your sealant.


How big should the checks be before you seal them?

Ideally, you would seal all upward facing, weather-exposed checks. However, checks get small enough that it is very difficult to apply a sealant to them. Seal whatever you can, but don’t try to fill hairline checks. We always advise filling side facing or upward facing checks that go into windows or doors to prevent water intrusions into the frames. Spiral checks that twist into the interior of the house should also be sealed up.

What do you use for sealing up your checks?

Regular caulking is generally not a good choice to seal checks. Our Check Mate 2 specifically developed for this purpose. It is colored to match our exterior stains and available in tubes to make an application easy.

Even though Check Mate 2 is our preferred sealer, some customers use Energy Seal for the purpose. When you are sealing checks, use a line of masking tape along the edge of the check to keep the sealer off the surface of the log. This works whether or not you already have stained the logs.

If the wood within the check is dump from cleaning, rain or borate treatment (it is important to treat an existing check with Shell-Guard RTU before sealing it), make sure the check has time to dry before applying Check Mate 2.


Watch our video that teaches how to seal checks here

Remember to use a backer material to keep the sealant thickness between 1/4 and 3/8 inch. Also fill the check completely up and a little beyond the log surface to allow for some shrinkage for the sealant as it dries.

Last modified on Tuesday, 31 July 2018 16:52

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