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by Andy Engel

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Who came up with the first hidden decking fastener is open to debate. Weston Leavens remembers first seeing them in a magazine sometime around the end of the Reagan administration. A screw or nail affixed the clip to the first board and to the joist, and the second board was driven onto a prong protruding from the first clip.

At the time, Leavens was the owner of one of the largest deck-building companies in San Diego. Intrigued, he ordered a box of the fasteners and used them to build a display deck for the annual home show. "The deck moved and squeaked," says Leavens. "It was embarrassing. I thought we'd done something wrong, so I called the magazine and eventually got in touch with the author. It happened that the deck featured in the article wasn't far away, so I arranged a visit. Well, it squeaked and moved, too, but the owners didn't seem to mind." That experience led Leavens to invent the Deckmaster, a track system that he began to use in his own business in about 1989.

That was a fertile time for the hidden-fastener industry. Sometime in the early '90s, Harry Eberle was working on a high-end house in Hunterdon County, N.J., and as seems common with busy builders, his mind was in two places at once. While he was using a biscuit joiner to put together the cabinets, he was also noodling out the best way to fasten down the furniture-grade ipe for the deck. In that circumstance, I'd probably have managed to misalign a couple of biscuits. Eberle invented the EB-TY.

Concealed deck-board fasteners now come in a variety of flavors. It seems that the prong type was the first, followed by tracks, biscuit systems, and, recently, clips that either interlock or fit in grooves cut down the sides of the boards. The newest development is composite decking systems that come grooved for a proprietary clip from the manufacturer. Ipe and other hardwoods may be available locally with similar grooves milled in. As with nearly any product, some users get good results, and others don't. Below are a few things to consider, to make the most of hidden fasteners.

Exposure

All hidden fastener systems solve one obvious problem, which is that of being exposed. It's more than just an aesthetic issue. The movement of wood or composite decking that's been exposed to the rigors of the outdoors commonly results in nails or screws standing proud of the surface of the board. That's a trip hazard, as well as a minor annoyance to those inclined to take a snow shovel to their deck.

Movement

All deck boards move, but in different ways that depend on the material. Wood expands and contracts mostly because of changes in moisture content. Composite decking, on the other hand, expands and contracts with changes in temperature. Deck builders ignore these facts at their own risk.

Wood decking should be installed at a moisture content that's appropriate for the climate. For example, if you install kiln-dried decking in, say, coastal Washington, it's going to expand. It can expand enough across the grain to buckle, no matter what type of fastener you use. Go to a drier area and install wet decking, and you can count on it shrinking. Anecdotally, that can be a particular problem with some biscuit and pronged types of fasteners. In some cases, boards are said to have shrunk enough to disengage from the fasteners. Using lumber that has the correct moisture content for the climate should avoid such problems.

Composite decking that's installed at a high ambient temperature will shrink as the weather cools. Install it in the cold, and it will expand as the temperature rises. Pay attention to the manufacturer's instructions regarding installation in extreme temperatures.

Structure

Since we're talking about wood movement, we should also discuss deck movement. Several people I interviewed for this article spoke of experiences where decks built with a variety of concealed fasteners moved and creaked. A conversation with Frank Woeste, Ph.D., P.E., professor emeritus at Virginia Tech, confirmed one possible reason for this.

Traditionally built decks, where 6-inch nominal decking is nailed or screwed with two fasteners to each joist, are stiffened against lateral movement by the diaphragm this construction creates. This is similar to how a house floor is stiffened by the plywood sheathing, and although the strength gain offered by 6-inch planks isn't what you get from 4x8 sheathing, it's still significant.

Concealed fasteners may not provide the same rigid fastening that creates the diaphragm effect in a traditionally built deck. In fact, due to plastic's high coefficient of expansion, many fasteners that are intended for use with composite decking are designed to allow the decking to expand along its length. Attaching decking in a way that allows movement by definition will lend less rigidity to the structure. It would appear that only systems that rigidly attach each deck board in two places to each joist could come close to replicating the diaphragm created with 6-inch decking and exposed fasteners.

Leavens says, "The tightest any deck will ever be is on the day you finish building it." It's indisputable that time and weather take their toll on outdoor structures. One method to give any deck — whether built with concealed fasteners or not — a shot at a long, safe, and creak-free life, is to build redundantly with lateral bracing. Doing so becomes more important as decks increase in size, because larger decks and higher columns exacerbate any movement.

I would consider adding cross bracing below the joists, or beefing up the angled braces between the deck's support posts and its main beam, and I'd ask my structural engineer to consider this issue in his design. Additionally, some manufacturers recommend using an adhesive such as Liquid Nails or PL 400 with their hidden fasteners to improve the performance of the decking as a diaphragm, and to alleviate potential squeaking.

Water

One other potential issue is common to most hidden fasteners and to all exposed fasteners. In time, water can follow these fasteners down and into the heart of the joist, where the preservative often doesn't reach. It makes sense that this process would shorten the life of joists and decking. Leavens is certain of this, and claims one advantage of the Deckmaster to be that its screws are installed in the side of the joists, not the top. Another response to this concern would be to use one of the self-sealing joist tapes on the market.

Time

The final issue that's raised when talking about hidden fastening systems is labor. I don't think anyone in the industry would argue with the statement that it takes longer to install concealed fasteners than to use a nail gun or a collated screw gun to fasten decking from above. The solution is to sell hidden fastening systems as the upgrade they are.

Manufacturers are aware of the time concerns, as well. Some of the newer systems claim labor savings over earlier concealed fasteners. Initial reports regarding the labor savings offered by the pre-grooved composite lumber systems, for example, seem positive. Paul Mantoni, a Connecticut deck builder who's been using Tiger Claw fasteners for some time, says that their new TC-G fastener, privately labeled as Fiberon's Phantom, "saves a ton of time."

Andy Engel is the editor of Professional Deck Builder.