Teak can be found on battleships, on the Titanic, and on countless recreational boats. Prized for its durability and natural nonskid properties, teak has been the material of choice for decks. Its resistance to rot sets it apart from almost all other hardwoods, and native tribes in Southeast Asia used it medicinally for headaches by brewing a tea from the bark.
Ironically, though, teak decks can be a major headache for a boat owner.
A BIT OF HISTORY
As late as the 1960s, teak decks consisted of thick planks, perhaps 1¼ inches thick, screwed onto wooden deck beams. Let’s pause here and lay out some terminology:
Caulking: cotton placed into a seam, usually by hammering with a mallet and a metal wedge called a caulking iron.
Caulking seam: an opening created between the planks to provide a space for the caulking and seam compound.
Seam compound: a sealant poured or pressed into the top of a caulking seam to keep water out. Once upon a time, sailors used hot pitch.
Bung: a wooden plug driven into the hole created for a screw. The bung (also referred to as a plug) covers the screwhead and keeps water out.
In the old days, a caulker using a special mallet drove cotton strands into the seams. Hot pitch poured on top of the cotton created a seal (referred to as “paying” the seam). As the wood and cotton swelled, the compression created a mostly watertight seam. This practice created not only a heavy deck, but also one prone to leaks as the wood dried out on hot days or inside a winter shed.
To reduce cost and create a more watertight deck, builders shifted to installing teak over underlying plywood or fiberglass subdecks. With the subdeck providing most of the strength, the teak planks could be much thinner, usually three-eighths of an inch to a half inch (and sometimes thinner still). With less concern about leaks into the boat, the cotton caulking became unnecessary, but paying the seams with a sealant continued.
This change provided several significant advantages: watertight decks, less weight and reduced consumption of teak, without sacrificing its aesthetic and functional advantages. As so often happens, however, the new method brought some new problems.
MODERN TEAK DECK ISSUES
Foot traffic and repeated cleanings gradually wear away the teak, reducing its thickness. How quickly it thins depends on the frequency and aggressiveness of the cleaning; a one-eighth of an inch deck thinning over 10 years would not be unusual.
Initially, the wear impacts two important components: the bungs and the seam compound. The bungs become the first indication of wear: They eventually become thin and come loose. This condition presents more than an aesthetic problem. The bungs serve a critical function: keeping water away from the screw. Once water gets in, it can travel down the screw threads and into the subdeck. On a traditional deck, the deck beams will rot, while on a modern deck, water will get into the subdeck. For this reason, missing bungs require attention.
At this stage, the screw must be backed out, the hole drilled a bit deeper, and a new bung fitted. A traditional teak deck, with planks more than 1 inch thick, has plenty of room for the screw to be sunk more deeply and for a bung matching the original thickness). The thickness allows for the process to be repeated several times after continued wear. A modern teak deck does not provide the same allowance for bung replacement. By the time you allow for the bung thickness and the screwhead thickness, not much wood remains under the screwhead.
Sinking the fastener a little bit deeper will be the best you can do, and that means a thinner bung than the original. Setting the bung in epoxy will help it remain in place longer and will help seal the opening. After one round of refastening, not enough teak remains for another renewal in the future.
Now that we have seen what a nuisance the bungs can be, let’s look at one more important variable in teak deck construction. In the transition from thick, solid teak decks to thin overlays, the practice of screwing down the planks carried over. In the 1990s, the approach shifted to gluing the teak in place with only a minimal number of fasteners around the edges. Eliminating all those screws and perforations eliminates most of the bung and fastener problem. The difference can be easily identified: A screwed-down deck will have hundreds of plugs set in a regular pattern. Given a choice, the glued-down deck is far superior.
The seam compound also suffers with time. Seam compound fails for three reasons: age, adhesion and wear. Like all sealants, deck seam compound eventually breaks down. The material can start to crack and lose its elasticity. Seam compound must adhere to both sides of the seam and withstand the movement of the wood as it shrinks and swells with heat and moisture changes. Wear reduces the thickness of the seam compound and reduces the depth of the caulking seam. Once the seam compound has started to crack, separate from the sides of the seam, or visibly wear away, it must be renewed. If it’s ignored, then water will pass through the seam and find its way to the screws, following the path into the subdeck. Water in the core or in a plywood subdeck will create extensive damage.
Step one requires removal of the seam compound, sometimes with a special hot-knife tool or razor knife, and with a narrow hook (some use the heated and bent end of a file). After removing the compound, the seams must be cleaned to bare wood. At this time, the depth of the caulking seam must be assessed.
On a traditional teak deck, the seam will be a deep-V shape. As the teak wears away, the seam becomes a little shallower and slightly narrower, neither of which poses a problem. On a modern deck, there is a different situation: Width remains uniform, but the seam becomes very shallow. Depending on the deck’s original depth and the amount of wear, it may become necessary to recut the seam with a router to create enough depth for good adhesion. At least a quarter of an inch is recommended.
Assuming that you do not need to rout or cut deeper seams, you will need to clean the old seam well. Sandpaper wrapped around a thin metal plate works. (Teakdecking Systems sells a seam sander for this application.) Once you have clean and dry seams, one critical step remains: In order to allow the material to expand and contract as the wood moves, without losing adhesion to each side of the caulking seam, you must keep it from adhering to the bottom of the seam. A bond “breaker” must be applied to the bottom. Narrow, fine-line tape serves this purpose well (see photo).
With the seams properly prepped, it’s time to apply the seam compound. A number of products work well. We have had excellent results with SIS 440 from Teakdecking Systems.
After filling the seams and trimming the excess, the decks will need sanding. The lighter the sanding, the better, as you will be removing a considerable amount of teak.
MINIMIZING WEAR AND MAINTENANCE COSTS
Not much can be done about normal wear from foot traffic and normal aging of the seam compound. But we do have some options for protecting a teak deck.
Teak naturally turns from a lovely golden color to a distinguished and elegant gray. Some find the gray objectionable and routinely apply a special cleaner to restore the color. As a young man, I worked on a traditional wooden sailboat with a teak deck. The owner relished the fresh teak look, and every two weeks or so, he instructed me to bleach the decks. The chemical we used called for a dilution of 25:1, but in his quest for a brighter deck, we kept pushing the envelope, often going 10:1. With special guests coming one weekend, he told me to go 7:1 that Friday afternoon. On Saturday morning, the owner arrived with his guests for a daysail on Long Island Sound. The decks absolutely sparkled with that new teak look.
At one point the boat owner, after sitting on the deck, stood up near me. I looked in horror as I saw black lines running down the back of his snow-white yachting pants. The bleach had melted the seam compound, turning it into a sticky mess.
For cruising boats, most of us should be content with an annual cleaning. While caustic cleaners are effective, they can damage paint and the environment. ECO 100 from Teakdecking Systems works well without the harmful effects of acidic products. Some people report good outcomes with trisodium phosphate, or TSP, which is available in hardware stores.
Regardless of the product, three guidelines must be followed to minimize damage to your deck. First, never use a pressure washer, as it will dig away the softer grain, removing wood and creating a wavy surface. Second, never use a stiff scrub brush going with the grain; instead, use a soft brush or a Scotch-Brite pad. (For teak in poor condition, bronze wool might be necessary.) Third, don’t clean any more than you find necessary to your enjoyment of being aboard.
THE ENDGAME
Eventually, your deck will be too thin for proper bungs, and too worn to accommodate a deep enough caulking seam. At that point, the deck must be removed and a new surface applied. You will have three options: a new teak deck, a painted deck or a synthetic product that resembles teak.
Replacing teak with teak can be tackled in one of two ways. A skilled yard can mill, fit and glue the wood planks in place. Many builders and repair yards utilize the system offered by Teakdecking Systems. Templates or patterns are made on the boat and delivered to the company. It fits teak planks onto a backing material and ships the completed sections to the boat, where they are installed in large areas rather than plank by plank.
If you want to get away from teak completely, then the deck can be painted. For decks that were screwed down, the screw holes will be a problem, requiring filling and fairing. Although the nonskid provides some masking, the fill material in the screw holes will eventually print through as the sun heats the deck and forces additional curing and shrinkage. On some boats, builders relied upon the added stiffness provided by the teak, and if teak will not be replaced, then some additional lamination will be required to strengthen the deck. This determination cannot be made until the teak has been removed and the deck stiffness assessed.
In addition to teak and paint, we now have quite a few synthetic products to consider. These materials have nonskid properties similar to teak, and they bear a decent resemblance. Many tend to be hotter than teak, but they won’t turn gray. The cost and maintenance requirements will be well below teak, as will the expected service life.
Although costs vary among the choices, the differences are incremental, and you will have to weigh the savings against your preferences. If we consider a typical 42-foot powerboat with a teak foredeck, side decks and cockpit, then the costs might work out something like this:
Renew existing decks: clean seams and install new seam compound. Reset all screws. Sand the deck. $25,000. A renewed deck might provide another 15 to 20 years of service.
Painted deck: remove existing deck (assume no damage to deck core). Fill and fair all screwholes with epoxy. Apply primer and sand, and then apply paint with nonskid. $30,000.
Synthetic deck: remove existing deck (assume no damage to deck core). Fit and lay synthetic deck (product choice makes a big difference in cost). $60,000 with a better synthetic product.
Teak deck: remove existing deck (assume no damage to deck core). Fit new teak deck. $80,000.
The impact of your choice on resale can be difficult to assess. Higher-end boats might be expected to have teak, and if that has always been part of the boat brand’s style, then staying with teak might make sense. For the middle and lower end of the market, the absence of teak can enhance market appeal, as maintenance costs have been reduced. You also have the option to reduce the amount of teak, keeping a teak cockpit and/or flybridge, for example, while painting the side decks and foredeck.
Given the cost to renew or replace your deck, it pays to follow the maintenance recommendations and keep cleaning to a minimum. If you ignore loose bungs or deteriorated seam compound, then you risk adding tens of thousands of dollars in repair costs to the core or subdeck. A teak deck should give you 25 years of service.
Steve Zimmerman is the president of Zimmerman Marine, which operates five boatyards in Maryland, Virginia, North Carolina and South Carolina. Zimmerman has been building and repairing boats for more than four decades.
