Replacing a Wood Deck with Composite Doesn’t Mean Replacing the Substructure

Replacing a Wood Deck with Composite is easy

Replacing wood deck boards with composite revitalizes the deck and saves the existing deck substructure.

The first thing my friend did after closing on both his houses was tear out the old splintered wooden decks that came with them. Now, every time I go to his house, I have a problem. I end up chasing my friend’s rowdy yellow lab around the yard (because chasing down a big dog and wrasslin’ the toy back is great fun), and then stubbing my toe on, or tripping over, concrete. That’s because my friend decided to adopt an ‘as needed’ attitude toward removing the buried concrete post anchors that held down the decks he took out. If my friend had considered replacing his wooden decks with composite instead, I, and his other guests, wouldn’t have to nurse bruises from falls while pushing a drool-soaked toy and an eager dog away from our faces.

Most homeowners underestimate the maintenance a wooden deck needs, and never consider replacing a wood deck with composite, which requires far less maintenance. My friend, for example, inherited a splintery mess of a deck. He thought about the cost of replacing the deck, staining the new boards, sealing them afterwards and every other year to follow, and the likelihood that he’d still end up pulling splinters out of his family’s feet, and ended up demolishing the deck within a day–and did it again at his next house. My friend had never heard of composite boards, and never understood that resurfacing his wood deck with composite once would have solved most of his problems. Here’s why.

Why Replace Your Wood Deck with Composite Deck Boards?

My friend and most homeowners aren’t familiar with composite boards for outdoor decks. If they’ve used, or have considered using composites before, then they may be thinking of older first-generation composites which were heavier than wood, cost more, and didn’t hold up very well over time. They also tended to be slippery when wet. In comparison, modern composites from a quality manufacturer have the following advantages:

  • Scratch-resistance: Composite boards are a mix of organic material–like wood or bamboo–and plastics evenly blended together. They come in a variety of colors so they don’t need stain, and because this color is part of the board it doesn’t scratch the way wooden boards do. While a scratch on wood breaks through the stain to the bare wood, on a composite board scratches are much harder to notice, and if necessary can be blended back in with a heat gun.
  • Slip-resistant: Older composite boards had a reputation for being slippery, but quality modern composite decking boards are slip resistant because of their rubber-like resin coating, called a cap.
  • UV-Resistance: The coating on fully capped boards also helps them resist UV light and fading better than traditional wooden boards.
  • Moisture-resistant: Finally, composite boards are denser than their wooden counterparts for greater moisture resistance (the capping also helps with moisture resistance), and if the composite’s organic component is bamboo instead of wood then there are even fewer channels for moisture to make its way through the board.

All of these factors combine to keep composite decking barefoot-friendly and attractive looking over the long haul. Yet homeowners who are familiar with older composite boards, or are unfamiliar with high-quality composites, might be worried about putting in composite decking without building a new substructure. However, it’s perfectly possible and safe to do this. Here are some tips on putting composite boards in on top of your old deck’s substructure.

What to Look for in the Substructure When Replacing a Wood Deck with Composite

Fortunately for contractors and DIYers, over the last few decades standards have emerged in deck construction. Most existing wooden substructures—the vertical posts, horizontal beams, and joists—that hold up wooden decks are more than adequate to support composite deck boards. An easy way to tell the difference between these structural pieces is that the posts will be vertical. The beams of the deck framing will be thicker than the joists and will be anchored to the posts. Joists will be smaller than beams, there will be far more of them, and they will be attached to the beams. Joists are what you’ll put the decking boards on top of. If you’re looking to resurface a wooden deck with composite, the standards you’ll need to look for are:

  • Posts that are at least 4x4s. Dimensional lumber is half of an inch smaller than the numbers they are called by. This means a 4×4 post’s actual dimensions are 3½ by 3½ inches. By measuring the face, a homeowner can determine if their existing posts meet their needs.
  • Joists that are at a right angle to the deck boards above, and are spaced 16 inches from their centerlines. The centerline is usually the middle of a joist’s narrow side. A 2×6 joist’s centerline will be at the ¾ inch mark on its thinner side. On a small part of the deck, diagonal decking boards can improve a deck’s appearance, but these need to be supported by joists spaced no more than 12 inches from their centerlines. If you’re looking to put in a section of diagonal boards, it’s a simple modification to change the joist spacing beneath a portion of the deck.
  • Fasteners that are structurally sound and holding. A small amount of corrosion on bolts, nail heads, and washers is normal, but excessive corrosion can damage the fastener. This could lead to trouble when installing composites, which tend to be heavier than wood. Fasteners should also be inspected to ensure they have not worked loose as a result of the expansion and contraction of the wood substructure.

While your deck substructure is most likely pressure-treated lumber, I’ve seen steel substructures as well. These are a relatively new development in outdoor decks, and are also much stronger than their wooden counterparts. If you’re looking to replace a wood deck built on a steel substructure with composite boards, you can be confident that it will easily support the additional weight of composite.

Creating a Coherent Look for Your Composite Deck

For those keeping the wooden structure of their deck and just replacing the surface, a mismatched appearance may be another concern. Posts on the perimeter of a wooden deck often rise up through the deck to provide the posts for railings. That means that an existing post may be structurally sound, but won’t match the deck’s new look. Some homeowners may conclude that they need a new substructure just to get the appearance they want, but some composite deck manufacturers make complete composite deck systems. They’ll provide fascia boards, composite sleeves that fit over 4×4 posts, and composite stair treads and risers that fasten to the substructure to give an existing deck (and your home) a tied-together new look.

Replacing your wood deck with a composite deck surface is a great way to bring a sun-blasted, splintery deck back to life without the trouble and expense of having to build a whole new deck structure from scratch. Wood can be replaced with composite boards on a one-to-one basis, and when properly installed will last against the elements. If my friend had known about composite decks he could have kept his existing deck, enjoyed more time outside, spared me some bruises, and spared himself the trouble of digging out the post anchors. He may actually decide it’s easier to use them for a new deck than to keep letting me trip over them.

When he does, I’ll recommend Fortress Deck to him. My experience is that the composite decks that last are the ones in which even the smallest chance of a failure has been engineered out. Fortress Deck has engineered their Infinity composite decks down to the core, using bamboo instead of sawdust for greater strength and water resistance. Fortress boards use Hulk hidden fasteners to anchor the decking down without providing a path for water to penetrate to the core of the board. This system makes the boards even longer-lasting, and gives the deck an elegant, uninterrupted look. Fortress’ Infinity line of deck composite is also backed by a 25-year warranty. This solid engineering extends to Fortress’ other products like Fortress Railing and Fortress Fence, so if you’re looking to revitalize your deck, you can also revitalize your whole yard.

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