Outdoor Building Materials and How To Coat Them (Part Two)
Blue Door Painters, DC area coatings contractor, discusses the nature of various outdoor building materials – and the coatings that protect them.
My Deck is Made of . . .
. . . Cedar or Redwood
Is your deck naturally a warm, rich, reddish color? If so, it probably cost more to build than its green-blonde pressure-treated cousins – and it was probably worth it. Unlike the dry-climate conifers used in SPF and pressure-treated lumber, cedar – specifically, Western Redcedar – and redwood both come from trees grown in damp climates, which have developed natural moisture and rot-resistance. The heartwood of red cedar, for example (which is the part of the tree that has that beautiful reddish color), is infused with thujaplicin, a combination of related chemicals that have powerful anti fungal and antibacterial properties. Redwoods offer similar protection.
However, if your deck, fence, or siding is built from cedar or redwood, you need to make sure that it is constructed primarily – if not solely – out of heartwood. Heartwood is the wood located at the center of the tree, which is not actively engaged in nutrient cycling and metabolism. The active outer wood, called sapwood, has not developed rot-resistance because it is still protected by the tree’s living defenses. The larger the tree, the higher the percentage of heartwood – but with old growth forests dwindling and an increasing need to protect these resources, more and more cedar and redwood is harvested from newer growth tree farms. The percentage of heartwood coming from these younger trees is much lower, leading to wood that has neither the color nor the rot protection that has come to be associated with redwood and cedar.
If your exterior cedar or redwood is largely sapwood, it should be treated with the same care and attention given to SPF or other vulnerable types of wood: either stained and coated with a strong water-repellant sealant, and re-coated regularly, or primed and painted with a solid stain or appropriate wood-protecting exterior paint. If the wood project is heartwood, then it ought to be regularly stained and treated with water-repellant sealant to ensure that it retains its beautiful warm red tones (which will bleach out without re-staining), and that moisture does not warp or crack the boards.
. . . Composite Wood?
With all of the care and maintenance required for a natural wood deck or fence, the call has gone out to the innovative: can we manufacture a better alternative? The best answer on the market to date is composite wood. Created from a mixture of recycled plastic and wood chips or sawdust, composite wood is crafted to look like wood, but to share none of wood’s vulnerabilities. The plastic in the mixture protects the wood from rot and moisture-induced warping, and because the wood is factory-uniform, its performance is more reliable. Composite wood is easy to clean, and does not require the same degree of protection as its natural counterparts. For many, the benefits of composite wood outweigh the extra cost, artificial look, and colder feel of the material.
However, despite being heralded upon its arrival on the market as a “zero-maintenance material”, composite wood is still vulnerable to both mildew and color change if not properly protected. Due to its density, composite wood projects often develop small, tightly clustered pinpricks of mildew, and the color of the wood pulp included in the mixture will change in the elements just like any other type of wood. To ward off mildew, the use of a special composite deck sealer is recommended, in conjunction with periodic cleaning with a combination of bleach and water (pressure-washing with a composite wood mildew removing detergent is an ideal method of cleaning). And staining the deck every five years or so can correct the color change; just make sure you use a stain that is intended for use with composite wood products.
In conclusion, all wood-based outdoor building materials require some TLC, and applying the right coatings at the right time is a critical element of that care. Being in the know about your deck, fence, or siding, and its specific strengths and vulnerabilities, is the best way to maximize your relationship with your outdoor space.