Bending Boards to Build a Beautiful Deck
Updated: Dec 31, 2021
(guest post courtesy of Kim Katwijk of Deck Builders Inc.)
The ability to bend man-made decking materials is taking builders and homeowners to new heights of imagination and creativity. All you have to do is look at the recent winners of NADRA’s (North American Deck & Railing Association) national deck competition to realize curves are where it’s at.
If you are a homeowner thinking of upgrading, replacing or building a new deck, you might be wondering if you can create the deck of your dreams yourself, or will you need a professional? After reading this article, you should have a pretty good idea of what it takes to create a curvy deck.
A Literal Learning Curve—My Journey into Board Bending
I am in my 25th year of building decks full time. With that many years of experience under my belt, I guess I qualify to fill you in on how it’s done. But first, let me confess my failures.
My first attempts at board bending were with Trex decking some twenty years ago. I had built a curved Cambara wood deck for a client. The client wanted a curved railing to match, so I thought I’d try to heat and bend a Trex composite deck board as the top railing board.
The first heating apparatus I created was a 20-ft. long by 20-in. diameter Sonotube laid on the flat with rebar shoved through the sides to suspend the decking. Two kerosene space heaters forced hot air into each end of the tube. This method produced uneven heating and dismal results.
Next, I tried a water-bath heater using a PVC pipe cut in half lengthwise. I glued four inlets into the half-pipe, then inserted a water tank heater into each inlet. I was able to heat the water to boiling. After an hour of boiling a board, I could bend a 20-ft. composite board to a radius of about 18 feet. That’s not very good. To get the 5-ft. radius I needed, I had to rip the composite boards into three strips, heat them, bend them to a 5-ft. radius, then glue and screw them back together. It was passable.
On another project, I tried to get higher temperatures by insulating the pipe and capping it with rigid insulation. This succeeded so well that the tank melted.
I gave up on bending deck boards until, at a trade show, I discovered the Heatcon bending system. Working with this system, I was able to bend a flat piece of 5-1/2-in. Azek cellular PVC decking to a radius of 22-1/2 inches. Impressive! This opened the door to new levels of artistic expression.
I used Heatcon with great success for years, but when it came to bending Trex Transcend capstock boards, the system would end up either not heating the core layer enough to bend, or it would melt the softer top layer and ruin the embossed grain patterns.
In 2016, I was with other professional board benders at Bendfest in Seattle. The discussion turned to the problem of bending Trex Transcend capstock. My friend, Jason Russell, brilliantly came up with the idea of using two Heatcons set at different temperatures and cross blanketing them. This just might do the trick! And yes, it worked, the downside being now you needed to buy two units instead of one. I approached Heatcon about developing a dual control unit, but that was not something they were willing to do.
Two and half years later, I developed my own system, and started my own company, Inblazen—heating gear with dual-control skins. Voilà! Capstock bending problem solved!
Design Your Dream Deck
All good things begin with a plan. If you have a hard time seeing how something will look just from a drawing on a paper, you’ll probably want to hire a professional deck designer/builder. If you are imaginative and determined, you can design your own dream deck with the help of a good software program. Most top deck builders use Real Time Landscape Architect http://deckdesignsoftware.us/. At $400 for the software, it is very reasonably priced. It’s quick and easy to learn the program, and the 3D photo realistic renderings help you visualize how the deck will look.
If you are serious about creating your own deck masterpiece, you will need a way to heat and bend the boards. To be fair and thorough, let’s look at your choices. There are three systems designed for board bending.
Priced at $8,499.00 plus shipping
Comes with a Forming table 4’x8’
Able to heat two 8’ boards at the same time
Able to heat railing, decking and trim
Adjustable temperature up to 300° F
Weighs 330 lbs., 24”H x 40”W x 128”L (need a fork lift)
Operates on LP gas and 110V, 15-amp service
Having used this system, I find that 8-ft. boards are just too short. You can never use all the board, so having a joint every 7 feet is annoying. Their table is nice to work with, especially when you try to bend railing.
$2,700.00 plus shipping for a 10’ kit
2 - 8″x10′ heating blankets
Adjustable temperature up to 300° F
Able to heat a 10’ deck board
2 kits can bend 20’ boards
Operates on 110V, 15-amp service
Weighs 25 lbs., easily carried and stored
Heatcon’s web page states, “Not recommended for capstock materials.”
• InBlazen – Heating Gear 360) 591-1448
$2,500.00 for 10’ gear (Also comes in 12’ gear)
2 - 8″x10′ Heating Skins
Adjustable temperature up to 350° F
Dual control (Each skin can be set to desired temperature independent of the other, specially designed with all Capstock decking in mind.)
2 kits can bend 20’ deck boards
Operates on 110V, 15-amp service (option of 240 volts for worldwide use)
Weighs 25 lb., easily carried and stored
Both Heatcon and InBlazen heating systems need insulation. We use Ultra-Touch Denim Insulation, because it’s more pleasant to work with than fiberglass.
The heating method is to lay down the insulation on a flat surface like a garage floor, then lay the skin or blanket on top of the insulation, then the board face down, then the second skin or blanket, and finish off with the second strip of insulation. This is how all bending is done. If it is wet or windy, we will put down plastic sheeting, and then fold it over the whole pile to hold in the heat and keep it dry.
Which Decking Materials are Best for Bending?
The array of composite and PVC boards has increased dramatically over the past twenty years. Because it’s my business, I try diligently to know the pros and cons of most of them. Any man-made decking that contains plastic can bend, but how well each of them bends is variable.
How tight can you bend a 5-1/2-in. wide board? It all depends on the makeup of the decking. The tightest that I know of is 8-1/2-in. inside radius in a 360° circle with ClubHouse Decking.
I have independently done my own field evaluations and bend testing of numerous boards. There are some types of decking that are fine boards, but are not formulated for bending. Following is the list of boards that I have tested and which ones are suitable for bending.
ClubHouse Decking bends easily, is dimensionally stable, and has a warranty that stays in effect even on bent boards.
Inteplast / Wolf Decking
Inteplast and Wolf boards can be bent to an inside radius of 3’ or less.
Azek decking can be bent to a radius of 4’ or less. The tightest I have achieved with Azek was a 22.5” inside radius. Boards will swell a tiny amount when heating.
Fortress and Moistureshield are capstock. Bends easily to about a 6’ radius.
Trex Transend decking
Trex Transcend is a capstock. It can be bent to an inside radius of 10’ or less. The tightest I’m aware of is an 8’ radius. This is where InBlazen really shines. By heating Trex face down and setting the lower skin at 200° and the top skin at 260°, Trex can be bent to under 10’ without melting and distorting the grain pattern.
Capstock. Can be bent to 14’ radius.
True North Decking
Capstock. Can be bent to 15’ radius.
Capstock. Heritage™, Vista™, and Classic™ can be bent to 15’ radius.
Capstock. Can be bent to 15’ radius.
Capstock. Can be bent to 16’ radius.
Cellular PVC. Usually bends easily, but when temperature is high enough to bend, the grain pattern begins to vanish.
Deckorator Eovation Decking
Does not bend.
(Note: If I do not mention a particular brand of decking, it is because I have not been sent any boards for evaluation.)
Framing for a Curved Deck
Once the joists are in, you will put a nail in the center, attach one end of a wire to it, attach a pencil to the other end of the wire, and use this like a compass to draw the curve on top of the joists. Now, you have a line to follow as you skillfully cut the joists using a chainsaw. Yep, that’s how I do it. The chainsaw will allow you to cut any angle.
After cutting your joists, you need to cut blocking to install between the joists. This makes your rim. If you plan to install a ribbon to trim the outer edge of the deck, use another set of blocking to support all the board ends. All boards must be supported within 3 inches of the end.
Inlay and patterns in the deck
Inlays and patterns can be a lot of fun. Just remember that every piece needs adequate support beneath. This can be done with blocking to support both sides of every piece of the design, or—a slick trick to use, especially when the design has many small pieces—install a 1-in. fiberglass grid beneath the design. The grid can be obtained from McNichols Fiberglass Grating.
Whether you choose to tackle the job of doing it all yourself or to find a professional who can bring your ideas to life for you, beautiful outdoor living spaces with free-flowing, curving lines are now available to homeowners around the world! Bending technology allows your imagination to flow as you think outside the box to create the thing we call a deck.
WATCH THE INBLAZEN SYSTEM IN ACTION!