Treated lumber, or composite? This is a common question when meeting with a client to discuss a design regarding a deck build. There are pros and cons to either path. It really comes down to the preferred style, the cost to build, or a combination of both. But, keep in mind, a composite deck is still supported by treated lumber, even though it may not be visible.
A composite deck is likely going to cost more to build. Although the composite top-decking and fascia installation process closely rivals that of treated lumber, it is the product cost per lineal foot that increases considerably. On average, treated top-decking two-by-six boards cost roughly $1 per lineal foot. Comparatively, a single-tone composite top-decking board may start at $3 per lineal foot, and can easily reach $8-plus per foot when choosing higher-end dual-tone boards.
This can double, triple and even quadruple the cost of your total deck project.
The upside to the greater expense is the lower maintenance factor over time.
Although treated lumber can last years, possibly a decade or more before it requires any staining or oiling, a composite deck is deemed maintenance-free from the onset. And for that reason, many clients have opted for composite top-decking and fascia.
Last summer, the first composite deck I built would eventually hide all the treated support lumber below. The treated lumber ledger boards were first fastened to the exterior wall. The main beam and support joists (also treated lumber) were set into place and the stair stringers were fastened to the outer frame — a typical start to any deck build.
There were, however, some hidden adaptations for the impending composite top-decking and fascia installation.
The client chose a light grey Trex product for both the top-decking and fascia.
The top-decking Trex boards are roughly one inch thick, lending less structural rigidity than a standard two-by-six lumber board (which is actually 11/2 inches by 51/2 inches after being planed, smooth). As such, it is necessary to place joists on 16-inch centres for composite, as opposed to the standard 24-inch centres when topping with lumber.
The Trex top-decking runs parallel with the back of the house on this build, at a distance of roughly 19 feet. Luckily, Trex boards come in 20-foot lengths, which allows complete boards with no seams.
The Trex fascia boards, however, are manufactured at 12-foot lengths only. Therefore, it was necessary to provide vertical supports along the perimeter of the deck on which these fascia boards could be affixed, and a few staggered seams were necessary.
Trex installation is quite simple. There is a groove on either side of the top-decking boards. Clips set into these grooves are fastened to the joists below, between each of the boards during installation, rendering the top-decking free of any fasteners.
This is not the case with the fascia boards. Counter-sinking hex screws leaves a small hole that for some lines of Trex can be filled by purchasing same-colour plugs.
For this project, no plugs were used. Once the top-decking was installed on the main deck as well as atop each stair, the fascia was then fastened to the perimeter of the deck’s framework starting from high to low. The fascia boards are the same width as the rise of each stair, allowing the fascia to continue as horizontal and parallel rows of boards all around the outside of the deck.
As the final task to complete this maintenance-free deck, a custom privacy wall was erected along the far side of the deck. Four white powder-coated, six-foot top-mount posts were fastened to the top edge of the deck, perfectly level and equidistant from each other. A 3/4-inch u-channel was welded to either side of both inner posts and along the inside face of each outer post. Decorative white plastic privacy panels, three groups of three in total, were then slid into position, providing some eye-pleasing, yet sought-after shelter along the far side of the deck.
And with the privacy wall in place, this beautiful outdoor space had been realized.
Maintenance-free can sometimes be a misnomer — Trex composite top decking and fascia, as well as the powder-coated posts and decorative plastic panels of the privacy wall, are certainly akin to being free of upkeep.
However, we can’t dismiss, nor forget about what lies beneath. Over time, the harshness of the elements will eventually begin to erode the integrity of the deck’s structure below — it’s inevitable — but fortunately many years, even decades, away from happening! And when that day finally comes, no doubt the deck’s exterior will appear the same as the day it was completed.