The Magazine

• Home
• Advanced Search
• Current Issue
• Past Issues
• Topic Index
• Monthly Survey
• Past Surveys
• Editor's Corner

Fastening Deck Boards

Speed of installation and cost are important, but so is long-term performance

by Kim and Linda Katwijk

Twenty years ago, choosing a deck fastener was easy — decking was wood, and we nailed it down (Figure 1).


Figure 1. Nailing remains a viable and effective way to fasten decking, particularly when price is a big consideration.

Then Trex composite decking came along and introduced a problem: It mushroomed when nails (and the screws of that time) were driven into it. Within a few years, the number of alternative-decking manufacturers had grown to 80 or more. That led to the development of numerous fastening systems, to deal with mushrooming and other issues. I don’t evaluate all available fasteners in this article — if I don’t mention a fastener, it doesn’t mean it’s not a good choice. I do explain, in depth, why I choose the fasteners I do.

My main question when choosing fasteners is “How is this fastener going to perform over the life of this deck?” I consider a number of factors, from corrosion to holding power to whether a system creates a situation where freeze-thaw cycles can damage the decking. How you weigh those considerations will depend to a degree on where you build. Freeze-thaw cycles, for example, aren’t a concern in Miami. On the other hand, accelerated corrosion from salt spray might be, and how much shear strength a fastener contributes to the deck in a hurricane is also likely to be important.

Of course, no matter where you live, speed of installation will have a big bearing on profits.

Corrosion Resistance
By now, most deck builders know today’s ACQ preservatives are far more corrosive than the CCA they replaced. Even so, hot-dipped galvanizing (although in a thicker coating) has remained a popular way to add corrosion resistance to fasteners. For decks in wet conditions, however, stainless steel fasteners may be preferable to galvanized ones, according to testing done by Simpson Strong-Tie (strongtie.com/ftp/fliers/f-deck code09.pdf). The company also points out that “some treated wood may have excess surface chemicals, making it potentially more corrosive. If you suspect this or are uncertain, use stainless steel.”

My own testing also supports the use of stainless steel. When ACQ-treated wood was first available some five years ago, I drove hot-dipped galvanized nails and screws (all of which met the code-referenced standard ASTM A153) into some samples and threw them outside. I opened up two samples the first year (Figure 2), another one after two years, and two more when I wrote this article. I was troubled by what I found after just one year: As I gently split open the wood, the nails pulled away from the galvanizing, which stayed attached to the wood. White rust was on most of the steel, and some red rust was on one nail. I use the photos shown here to upsell stainless steel to my clients. Unfortunately, most of my competition uses galvanized fasteners, which puts the more expensive stainless at a disadvantage.


Figure 2. After one year’s outdoor exposure in Olympia, Wash., galvanized fasteners driven into ACQ-treated lumber have begun to corrode (left). After five years in the same environment (right), rust is apparent everywhere.

Many anti-corrosion coatings are available in addition to zinc (galvanized), including ceramic, silicon bronze, and silicon copper. These alternatives are all cheaper than stainless steel. One way to compare the different coatings is to look at the results of accelerated salt-spray testing, which most manufacturers publish. Some fasteners begin to rust after 300 hours, while others are claimed to last 3,500 hours. Salt is very corrosive and the test is easy to standardize, but it provides limited information. Even a number of fastener and treating-chemical manufacturers admit that the salt-spray test doesn’t predict how long it will take a fastener to corrode in a real deck in a particular environment in contact with a particular treating chemical.

Speed = Profits
Speed of installation is where profits lie. The fastest way to fasten down a deck is with a pneumatic nailer. You can use ring-shank nails or UFO Ballistic NailScrews (Universal Fastener Outsourcing; 800/352-0028, allnails.net). The thing I like about the NailScrews is that they can be backed out using the screw head (Figure 3). (Tip: I’ve used UFO Ballistic NailScrews on cedar decking, but the plastic collating marred the wood. The wire-collated screw nails, however, work great with cedar.)


Figure 3. NailScrews are relatively new to the market. Driven with a pneumatic nailer, they’re as fast to install as any other nail, and their heads allow them to be backed out or driven deeper with a screwdriver. Photo credit: Universal Fastener Outsourcing.

The second-fastest method I’ve found is to use a collated screw gun (Figure 4). I’ve tested every one that I have been able to get my hands on. Most screw guns don’t let you see exactly where you are placing the tip of the screw, making precise placement difficult. Most screw guns also make you stand or place your body in an awkward position to operate them. Muro has solved both of these problems with its FDVL41 Speed Driver.


Figure 4. Nearly as fast as nailing is face-screwing with a collated-screw gun. Screws can be had with heads in a variety of colors to match most composite decking brands.

Slowest are the hidden fastening systems — clips, pound-on clips, screws and plugs, screws through the edge of the board, screws from the bottom, screws to the edge, clips that slip under the existing fastened board, and a few others (see “Hidden Fasteners,” July/August 2007; free at deckmagazine.com). I’ve tested most and tried some and, as a result, can shout the praises of two. Of the hidden fastener configurations, the least slow are the clip systems that work with pre-grooved boards (Figure 5).

Figure 5. Hidden-fastener clips usually have either prongs that are driven into the side of the deck board (left) or tabs that engage in grooves milled in the side of the decking (right). Photo credits: Tiger Claw, Fiber Composites.

Although I try to upsell every potential client to a hidden fastener system (see Deck Ledger, “Creating Upselling Opportunities,” May/June 2009; free at deckmagazine.com), the additional cost of $4 to $5 per square foot is too much for most clients. The main reason for the extra cost is time. You have to hand-feed two things, the clip and the screw, for each joist. As I write this article, only one hidden fastener system is collated (Figure 6) — the Tebo (Spotnails; 800/873-2239, spotnails.com). When others start to collate, the installation cost will decrease, and they may become more feasible.


Figure 6. The Tebo hidden-fastener tool drives a three-prong stainless steel staple. One prong goes into the joist and one into the existing deck board’s edge. The third prong faces outward, and the next row of boards is driven onto the prongs. Photo credit: Spotnails.

Concerns and Conclusions
On the majority of the decks I build, I use EverGrain or Fiberon decking. Unless the client wants hidden fasteners, I typically frame 1 foot on center and set one stainless steel or ACQ-compatible coated screw in each joist, alternating the side of the board that gets the screw. To hold the decking while it’s being fastened, I use a pin nailer to drive one nail in every third joist or so. Next, I use a 3/8-inch countersink bit to make a recess for the screws, and I predrill holes for any screws closer than 1 1/2 inches to the end of a board to prevent splitting.

Not that it comes up that often, but replacing a board is easier if you can unscrew it. With some fastening systems, you may need to undo many boards to get to the one you want. With other systems, you can only cut the board out and screw the new board back down. A finicky client won’t like that.

Even with hidden fastening systems, screwing down the decking provides the best holding power (meaning fewer squeaky decks and better lateral load transfer). I recommend either of two systems. The first is the DeckPilot system (Figure 7), exclusive to Fiberon Sensibuilt Decking (Fiber Composites; 800/573-8841, fiberondecking.com). Both edges of the boards are fastened with two 2 1/2-inch stainless steel screws at a 45-degree angle. The DeckPilot jig spaces the boards and guides the screws at the right angle, stopping them at the proper depth.


Figure 7. Fiberon’s DeckPilot spaces the decking and guides screws into the edge of the board at an angle.

My second recommendation is the Cortex Concealed Fastening System (FastenMaster; 800/518-3569, fastenmaster.com), a screw and plug system (Figure 8). The plugs match several types of PVC and composite decking, including EverGrain, Azek Deck, Trex Accents and Escapes, and TimberTech TwinFinish. The screw cuts a hole as it’s driven into the board. The proprietary bit has a stop that drives the screw to the correct depth for the plugs, which fit the holes perfectly. Once hammered in, the plugs are hard to see. Of the thousands of Cortex screws I’ve driven, only a handful of plugs didn’t fit — mostly due to operator error. If they ever automate this system with a collated screw gun, it will be near perfect. Cortex is the only hidden fastener that lets me choose the width of the gap between deck boards.


Figure 8. The Cortex system provides screws and a special driver. This combination countersinks the screw to the perfect depth for the supplied composite-decking plugs to be driven flush with the surface.

While they’re heavily marketed, I’m not sold on pre-grooved hidden fastener systems, even when the job’s budget supports them. First, my engineer advises the use of additional lateral bracing with them, which adds to the framing budget (see sidebar, “Does Decking Add Racking Resistance?”). My second concern is freeze damage. Although I haven’t had a callback for this yet, I worry the grooves will fill with dirt, animal fur, and leaf litter and then hold moisture. Over a 25-year lifespan, a deck may go through hundreds of freeze-thaw cycles. Will grooved decking give me trouble over its life expectancy? If so, I have to depend on my customers to get on their hands and knees to clean out the gaps every year. This is a particular problem in the Pacific Northwest, where we have lots of tree litter.

It would be less of a concern if any of the groove-and-clip systems allowed a larger gap than 1/8 inch to 3/16 inch. I use a 3/8-inch gap, which is probably wider than most builders use, to allow debris to fall through. The common big leaf maple in particular produces seed pods that will not slip through smaller gaps.

Kim Katwijk is a deck builder from Olympia, Wash., and a PDB contributing editor. Linda Katwijk is his co-writer.