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Care & Maintenance 

Wood Checks: Why does lumber split and cracks?


Checks and splits in lumber and timbers, especially pressure-treated lumber, are often misunderstood when assessing the condition of a structure. Decking splits as it dries. As the water evaporates from the wood in the sun, the surface wood shrinks cracking around the un-shrunk core wood or fasteners. The solution to prevent decking from splitting is controlling the pace the wood dries and providing room around the fasteners for the decking to shrink.


What is pressure-treated lumber checks?


Checking is the separation of grain that occurs in lumber as moisture levels change and timber dries. It looks like cracks and splits in the wood. They are two different types of deck splitting: structural end decking splitting and cosmetic field cracking of the decking. Cosmetic decking or in the industry called “checks” are unsightly but will not impact the structural strength of your decking. It may look ugly, but your deck can still be enjoyed for years to come. End splitting is a concern as these splits can crack through the full depth of the decking. Weakening the decking, where a foot could break through the decking.


Why does my deck post crack / checks?

Pressure-treated wood is softwood lumber, typically southern yellow pine, that's been chemically treated to resist rot, decay and termites. The boards are rolled into giant pressurized tanks where chemical preservatives are forced deep into the wood's fibers. The result is an exterior-grade wood that's ideal for building decks, fences, and other outdoor projects. Direct sunlight on a summer day can cause a timber to check dramatically, from all the moisture that was absorbed during chemical treatment process once exposed to the summer heat it will quickly dry out or shrink therefore creating checks.




Should I be worried about wood checks / cracks in my deck posts?


Checks and cracks actually help improve structural integrity because it releases the tension and pressure built up by shrinking wood. There is no way to prevent the naturally occurring process of checking from happening, especially when the wood will be used outdoors. Outdoor environments experience the most dramatic range of environmental exposure. From snow, inclement weather, pouring rain, howling winds, direct sunlight, freezing, thawing, high temperatures and low temperatures, wood that’s used outdoors experiences the full range of nature’s punishment.

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Was your reclaimed wood investment finished before you bought it or will you be applying your own protection? If not, varnish, polyurethane and lacquer are some of the most common and durable finishes you can apply in a properly ventilated space at home. Where a varnish can feel very smooth and gloss-like once dry, an oil will still allow you to feel the details in the grain. Oil finishes (including Danish and Tung oils) offer a more organic look by soaking deep in to the pores of your reclaimed wood and highlighting what's hidden beneath the surface. But an oil finish may require regular upkeep on average, one fresh coat every three or four years.

Once you choose your finish, you must decide on your tools of application brushes versus cloth wipes. When you paint, for example, do you confident in your brush work or do you reach for the roller every time? If the later is true, you may not enjoy working with a finishing brush and should opt for cloth wipes for an easier application. Another benefit of cloth is that you can rub and buff an oil finish until your face reflects within the surface, but brushing doesn't have much room for error and over-brushing can leave areas looking less professional. Whatever finish you choose, know that perfection isn't necessarily the goal and any small imperfections you add in the coating process with only enhance your product's character.


Even with the proper protecting finishes in place, reclaimed wood is still delicate and is prone to warping, discoloration and staining. When it's time to clean up, wipe dust off with a lint-free cloth. It may be a good idea to invest in a small brush to help you remove dirt, dust and other small debris from those hard-to-reach nooks and crannies. For a deeper clean, simple, natural cleaners work best: A blend of vinegar and water works well on unfinished pieces, and a natural cleaner, similar to Murphy® Oil Soap Original Wood Cleaner, is gentle enough to clean treated, reclaimed wood and still preserve and protect that unique character.

Caring and protecting reclaimed wood furniture pieces isn't nearly as intimidating as it seems. With some strategic finishes and smart cleaning habits, you'll lengthen the life of your swing, bench, or patio set for a long time to come.

      *Timber Image recommends: Sherwin Williams® SuperDeck Exterior Oil-Based Transparent Stain - "Canyon Brown"* 

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