Curving Composite Decking to Create Fanciful Deck Designs

Curving composite decking is tricky but rewarding.

Curving composite decking can be used to match trim pieces to the edge of pools, but also to create a fanciful design on the deck’s surface.

When most people build a deck, they’re looking for a place outdoors to gather with their friends and family or enjoy their coffee on a weekend morning. While they’ll pay attention to the appearance of the deck, it’s usually just to keep it level and all the boards straight. Less attention is paid to the deck’s surface design, and the majority of decks are simple shapes like squares and rectangles.

Sometimes, though, a homeowner will see something on a website or on the cover of a magazine that makes them consider other possibilities. These are decks where the boards alternate colors, or the designer went the extra mile to build a mid-century modern-style deck or a pool deck in which water-resistant composite decking is curved in a natural, elegant way. Other decks take on the shapes of leaves, with stems and veins picked out by differently-colored boards. Often these are made from composites for the simple reason that curving composite decking is easier than curving wood. This curving is done by using heaters that warm the composite until it is flexible. The composite boards are then fitted into a jig and bent as needed for the design. There are a couple different ways to do this heating, and each method has its own strengths and weaknesses.

Using a Heating Blanket to Warm Composite Deck Boards

One of the easier ways to warm composite boards to the point where they are flexible is to wrap them in a heating blanket. This isn’t to be confused with the electric blanket you break out in October when it’s time to snuggle up with a good book and some cocoa. A heating blanket is an industrial device made of rubber wrapped around heating elements. These are typically used for keeping sensitive materials from freezing, but there are versions that are explicitly meant for warming PVC or composite boards. They’re simply wrapped around the board and allowed to slowly warm the board up until it’s hot enough to become flexible. In order to do this properly you’ll want to follow the following steps:

  1. Lay down some insulation. You can simply buy a roll of home insulation, cut it to the length of the board you want to bend, then cut it in half lengthwise. Lay down half of the insulation on the floor or your work surface.
  2. Lay a heating blanket on top of the insulation. This will be the first of two heating elements used, and will heat the board from below.
  3. Place the composite deck board directly on top of this first heating blanket.
  4. Place a second heating blanket above the board in line with the first heating blanket.
  5. Cover the whole heating apparatus with the second piece of the insulation you cut in the first step.

This is a fairly simple setup to put in place, and it will reliably heat one board at a time. Heating blankets put out a low, even heat, and this makes for an evenly heated board that bends smoothly. Another advantage is that this simple setup is easy to transport and can be rolled up and stored until it is needed.

The biggest disadvantage of the heating blanket method is that it takes a lot of time, up to 30 minutes, to get a board hot enough. Also, you’re limited by the width of the blanket to heating one or two boards at a time, and it can take a long time indeed to finish a deck when you’re spending a half hour or more to install a single board. For many contractors, the length of time needed to warm the boards this way is a deal breaker. In order to speed things up on large jobs, quicker heating methods are needed.

Using Torpedo Heaters to Warm Composite Deck Boards

On larger jobs with many boards or very long boards that have to be heated, it may be practical to build an oven. For most people, this brings to mind a large permanent setup of steel cylinders six feet across in a workshop. These do exist, but they’re relatively rare in the world of decks. It’s rare that a deck builder has enough call for curved decks to justify that scale of investment. What most contractors actually use is a forced air heater blowing through some sort of pipe. Usually, the pipe is made of concrete forms placed together end-to-end and wrapped in insulation. A big advantage of this is that it scales to the length of your boards more easily than heat blankets can. There are some other advantages a torpedo heater has, too.

  • Speed is a plus, with the forced air heater putting out far more heat more quickly than heating blankets can. This speeds up the process of heating the boards as well as the job as a whole.
  • Cost is lower for a forced air setup than even the smallest heating blankets, and the tubes and surrounding insulation are relatively inexpensive as well.
  • Flexibility is greater for a torpedo heater system than a heating blanket. A forced air heater can be adjusted to heat longer boards simply by adding additional concrete forms to either end.

These advantages are a serious plus for contractors who may have a large deck design that they need to complete in a timely manner. However, these advantages come with some tradeoffs. An improvised force air heater rig has all the heat coming in from one point, and this inconsistent heat on the board comes with some disadvantages.

  • Uneven heating can leave spots in the boards that are cooler than the rest of the board. This can cause it to bend in unintended ways when it is flexed or make it more likely to break.
  • Set up is more difficult for a forced air heater than a heating blanket, and it’s less mobile. A forced air heater isn’t something that can be packed away at the end of the workday, and must remain on site until the job is done.
  • Cost can increase with the lengthening of the setup, and simultaneously the heat becomes less even and less reliable.

Overall, while a forced air torpedo heater is a quicker way to heat boards, and may be the only practical method for heating very long composite boards, it isn’t as reliable as using a heating blanket, and savings on the setup may end up being eaten by 54the cost of extra materials to replace boards that broke while being curved.

To avoid breaking boards, the rule of thumb is to go slowly when heating the material and to be patient with fitting it. In order to get the curves correct on your heated boards, you’ll need to use a form put together for the purpose. This type of temporary form is usually called a jig.

The Jig Is Up: Curving Composite Decking

As tempting as it may seem, it’s not recommended to build the deck’s substructure and then try to curve the heated board in place. The space between the joists will allow the boards to sag, and nailing blocks and other pieces of wood to hold the board in place can damage the substructure. Furthermore, nailing a semi-molten board into place can cause stress and tension on the board as it cools. The heated board should be shaped, allowed to cool, and then nailed in place.

The way to do this outside of the deck is with a jig. These can range from very simple to rather elaborate. A jig to shape a composite board starts as a simple piece of plywood. Large boards can be shaped on multiple sheets of plywood, while a single sheet of plywood should serve as the base of a jig for smaller designs like those for an elevated circular seating area.

Bending Boards for a Circular Seating Area

The perimeter of an elevated circular seating area is a common place to see curved decking. Composites boards can only curve so far before being damaged, so these tend to be made up of smaller segments of board pieced together from shorter curves to make the full radius of the circle. These small pieces are a good place to start developing a feel for curving composites. Here are the basic steps:

  1. Mark one-quarter of the circle on the plywood.
    • You can do this by tying a carpentry pencil to a string with a nail at the other end with the length of the string set to the radius (half the diameter of the curve).
    • Drive the nail into the plywood, pull the string taut and draw the curve.
  2. Nail short sections of wooden block to the plywood so that their faces are on this line.
  3. These blocks provide a molding point for a curve these will have to be very short pieces of wood.
  4. Place one end of the heated composite board against the wood that mark the radius, nail a small piece of wood on the other side of it to hold it into place and then pull on the other end using the leverage given by the length of the board to pull it into the curve made by the first set of wooden blocks.
  5. Nail additional pieces of wood next to the board to hold it in place as you move along the length of the composite board.

To create a full circle, it will be necessary to use multiple smaller segments of curved boards to make it. Essentially, you bend one-quarter of the circle into a board at a time, and then repeat. You then take these multiple curves along with the excess, and piece the circle together on the substructure, marking the pieces as you go. Only after holding the boards in place to the substructure and marking them do you cut away the excess.

A curving composite deck is not easy to build. It is, however, one of the most lovely things that can built onto a home, and will leave whoever steps out onto the deck impressed. If the builder of the deck is a local contractor, it will serve as a showcase for their company and their skills. A beautiful deck using curved composite boards is free advertising of the most effective sort, and when built right, it will last for years. To make the most of the hard work you’ve done and its potential to bring in business, use the highest quality materials. Durable, moisture resistant, and great-looking composite is essential.

Infinity composite decking by Fortress Deck is an excellent composite to choose if you’re looking to create a long-lasting, impressive deck to showcase your work. Fortress makes a fully-capped composite deck board with different finishes on each side of the board that can be mixed to create an organic look. It comes in a variety of realistic, complex colors, and instead of wood flour, Infinity decking uses bamboo for superior strength and moisture resistance. To find out more about Infinity decking contact Fortress or find a dealer to get started building. For more tough, stylish products from Fortress, check out Fortress Building Products’ full catalog.

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