There are two basic types of teak decks. Modern ones are decorative teak laid over a sub deck of fiberglass or other construction which forms the structural support. The traditional decks are planks of teak laid over a frame where the teak itself forms the structure of the deck. Re-caulking of a decorative teak deck is only necessary when there is physical deterioration of the caulking to restore appearance and to stop water damage due to trapped moisture under the wood. Re-caulking of structural teak decks is a continuous process which commences about 10 minutes after the deck was first laid and continues until the boat is abandoned. Teak should never be laid over steel plate decks. Inevitably the teak seams will leak and the trapped water will rust the steel causing it to swell and lift the teak off. On steel boats where deck webbing creates some areas where teak has to be laid over flat steel, the webbing should have as many holes cut in it as possible to allow water to escape and air to dry any cavities.

Traditional teak planks have cotton pounded into the seams when they are laid. This is quite an art and there are very few artisans left who can do it properly. The cotton serves a number of purposes. First it tightens the crack to minimize movement, and make the deck more contiguous. It seals the bottom of the crack so polysulfide (caulking) will not run through later. It is under high compression so it expands and moves with the teak when it moves. It absorbs water from a leak and swells to stop the leak. With modern polysulfide caulking compound I have found that pounding cotton into a seam while making repairs makes little difference and is not worth the trouble. If you have a crack that goes right through from a seam, by all means pound some in to stop the polysulfide running through (or tape it underneath with duct tape if there is access).

A groove is cut out of the top of each of the cracks between the planks to provide a cavity for the caulking compound. There are many schools of thought on the best shape of the groove cross section (width, depth, round, Vee, or rectangular) but here is my analysis. Teak deck caulking fails nearly always due to the caulking pulling away from the sides of the groove when the teak shrinks (dries out) and/or moves while underway. This would suggest a number of basic requirements:-

• The depth should be a maximum to provide the largest area for adhesion.
• The width should be a maximum to provide a larger block of rubber to reduce tension on the sides as it is stretched.
• The cross section should be a uniform width so that the stress distribution in the rubber block is equal at all points of adhesion so you don't create a starting point for it to tear off.

OK what are the practical limits?

• The depth can't be too deep or the structural strength of teak to teak is reduced and you would use too much of that expen$ive caulking compound. ¼ inch is absolute minimum, ½ inch is about maximum.
• Wide seams tend to look ugly. Those 1/16" thin black lines in a new teak deck look absolutely gorgeous even if they are trouble waiting to happen. I have found that with 2" wide teak planks, 1/8" seam width is the absolute smallest you should use. 3/16 will give you 50% less trouble. 1/4" will give you 75% less trouble. Wider than 1/4" tends to look too ugly. Wider planks will look OK with, and in fact will need wider seams because the expansion and contraction will be greater too. Decks expand, contract and move so unless that caulking is thick enough it is going to be sheared or pulled off the edge.
• A uniform cross section requires a rectangular groove. (Especially as it is much easier to produce with the skill saw than any other shape.)

Next a list of No Nos - absolutely forbidden things you should not even consider doing (and why).

• Never caulk a deck without masking off the wood. This is rather obvious however I have heard of people flooding the joints and deck with sealant and then sanding the sealant off the deck. A teak deck can last for 100 years but not if treated this way. Especially decks fastened from underneath (the best technique) since the ends of the screws will eventually start to arrive at the lowering surface and provide thousands of leak holes.
• Never sand a teak deck (unless you are keeping your boat in a museum). One of the beauties of teak is its non-slip quality. The grain of teak has softer and harder lines so the soft ones wear out leaving the hard ones as a perfect non-slip surface. Sanding to provide a slick pretty surface not only ruins the non-slip quality but the soft spots will wear out quickly and require re-sanding. Sanding reduces the depth of the caulking grooves, increasing the chance for a leak, and eventually requiring re-grooving.
• Never varnish a teak deck. You will ruin the non-slip quality, the varnish will not stick, it will discolor and make a nasty ugly mess.
• Hardly ever oil a teak deck. Teak does not need oil to maintain its quality, it has oil built in. A deck that has been exposed to the sun for 10 years without maintenance and has that white bleached look, has beautiful oily wood less than 1/100th of an inch below the surface. If you have just cleaned the deck (see below) and want it to have that honey colored look for a few days while you sell the boat, and you don't intend to actually use it, then the oil will do no harm.
• Never clean a teak deck with chemicals. Most will remove the natural teak oil and make the deck require more frequent cleaning. A functional (as opposed to decorative non-functional) teak deck requires virtually no maintenance - let the sun bleach it out to that greyish white look - that's how it is supposed to look. If you have soot, dirt, oil or other spills on the deck the best cleaning technique is a low powered pressure washer, with a little mild detergent where absolutely necessary. Stubborn oily/grease spots can be helped with a little pine-sol and a scrubbing brush. I have tried dozens of solvents but pine-sol does the least damage and seems to work well (especially on stubborn oily soot from paper mills!). This will remove the dirt and the bleached layer leaving a fresh teak finish yet do very little damage. Be careful to use only just enough pressure to remove the dirt, you don't want to raise the grain of the underlying wood. If there is no pressure adjustment on the pressure washer, use a wide angle nozzle and keep a larger distance from the surface to avoid damage.
• Never allow paint spots to land on the teak - always mask and use drop cloths when painting. Due to the non-skid finish they can be very hard to remove. The best technique is to allow the paint to dry thoroughly. DO NOT WIPE IT UP or use solvents. Allow it to set as thick as possible. Then a couple of months of sunlight and deck washings will eventually allow you to ping it off with a sharp point after soaking well. Again, the pressure washer technique is the easiest and most effective way of removing paint. Don't try to get it all each cleaning - leave what doesn't remove easily for the sun and weather to loosen up and get it next time.
• Never use substitute caulking compounds. The 2 part mix polysulfide seam sealants are the best. The 3M 101 sealant is a poorer second. No others work at all. See recent updates regarding new products, below. Hopefully in the near future they will come up with a formula that adheres better and has a little more flexibility since most decks leak where shrinking and moving teak has pulled the sealant off one of the surfaces. The seam material itself never fails unless you had a poor blending of the components in which case it stays as a black gooey nasty mess that will walk all over your boat.
• WARNING It has been reported and attested to by polysulfide manufacturers that some wood treatment finishes, in particular CETOL, can in fact cause the polysulfide to emulsify back to a black sticky mess. The process is slow, taking a number of months so be very careful what solvents and chemicals get on your seams. There is no warning on the CETOL product about this so be warned. It was also reported that the newer materials reported in the UPDATE below did not suffer this degredation.
  

• Wash it down daily with salt water. Teak expands when wet and shrinks when dry. If you allow it to dry, the rubber caulking between the planks has to expand as the teak dries putting the mating surfaces in tension. If they are well adhered, the rubber will stretch but any weak points will pull away opening up a fresh leak. Salt water is best because as it dries it leaves a fine salt deposit which will absorb moisture out of the air, especially at night and help keep the wood from drying out. It also reduces mildew and algae growth. If you aren't in salt water, fresh water is better than none.

List of tools you will need:-

• You need a tool to remove the old caulking. I understand that there are some fancy expensive rotating carbide wheel grooving machines which would be great if you can beg, borrow, steal, rent or even buy although I have never seen one and don't know how good a job they do. I make my own using a screwdriver ($3.00) Picture & Instructions.
  UPDATE August 2001. Although I have not tried it, a new tool has been recommended to me by Danny Kopels (dkopels@bigfoot.com) and others. They have nothing but praise for its speed, ease of use and the quality of the results. QUOTE "The blade won't cut the wood unless you really force it." It is the Fein Multimaster tool with a Teak Deck bit - see it at Sample Feinmaster Teak Blade source. Discount cost reported, about $169 for the tool and $41 for the teak bit. This tool works with a very high speed vibration rather than rotation like a router so there is no bias to moving it in a straight line. It appears the tool has a guide that senses the surface of the wood but allows the rubber material to compress and be cut off by the blade. This tool has received nothing but praise for its many other uses so that may help to justify the cost.
• You will need a Dremel tool to clean the groove, especially where it goes under deck fittings. Use the cheapest one you can find (about $45.00) - you don't need variable speed, you don't need the fancy carrying case and all those soft bits they supply. You will need a 1/8" solid carbide cylindrical tool bit, preferably with no teeth on the bottom. Get a second one in case you break one but I have found them to be very hardy.
• You should get a miniature skill saw. I use one which is about 4" in diameter. It was originally made for cutting ceramic tiles. Don't be tempted to get a battery operated one. Select one with high visibility around the saw blade, or open the cage up so you can see the cutting area very well. ($50 including shipping from Harbor Freight 800-423-2567) UPDATE August 2003. A reader reports considerably difficulty in obtaining saw blades to fit the Harbor Freight tool. Check compatibility before purchasing. At this stage the Makita 4 3/8" saw does have a carbide blade available but the arbor on the Harbor Freight saw is the wrong size to fit the Makita blade.
You will need a 4" carbide tipped blade. I use two, so one can be out for sharpening which they will require frequently despite the carbide. Non carbide ones will only last a few minutes in the teak, and the extra width of the carbide tips is an advantage here.
• A reasonably good shop vacuum to clean up the mess. ($75+/- at WalMart). Here is a warning based on personal painful experience. ALWAYS maintain the vacuum filter - what ever kind it has. You will be vacuuming up caulking cotton. Even a fine hole in the filter will allow this cotton fluff to get through to the electric motor. A ball or layer will build up around the brushes and with heat and sparking, eventually start to smolder. Even though you have pulled the electric plug, and been gone from the job for 3 hours, it has been smoldering and getting hotter until the plastic in the area starts to melt. Eventually dripping burning plastic will drop into the bottom bucket and set the rest of that cotton on fire. Hopefully you are in an area where your friends will see it and kick it overboard before any serious damage is done as they did for me. Another trick:- I purchased a remote control 110 volt switch from Radio Shack (about $22) and ran the vacuum through it. You can now have a long hose on the vacuum and use the tiny hand held remote to turn it on and off as required from the job rather than having to reach, or get up and go to the vacuum frequently to turn it on and off.
• About 3, five gallon plastic pails to collect nasty trash.
• A cheap kitchen style can opener. (You'll see why later.)
• A caulking gun (less than $2.00 at WalMart or equivalent). I prefer the ones without teeth that walk along a smooth shaft. The reason is you need to release the pressure every time you stop caulking to stop it dribbling. The gun with teeth takes two hands to hold and rotate the shaft, whereas the smooth shaft one has a release trigger on the handle that you can reach with your thumb.
• A box fan (if working in summer and specially if the no-see-ums are biting).
• A sun shade to keep the deck from getting too hot and you too.
• A carpet square to protect your knees and other parts.

Supplies you will need.

• 2-part Polysulfide seam Sealant. (About $20 to $30 per quart - use the cheapest, they are all the same). Although gallons are slightly cheaper you are much better off buying in quarts for many reasons. Get the "Pourable" grade unless the deck slope is greater that about 10 degrees and you have long runs when you might need the "Knife" grade to stop it running downhill as it sets. It is made by Life-Caulk, Gloucester, Detco and probably others, and available from Jamestown Distributors 800-423-0030, your local West Marine store or their catalog, and other marine suppliers.
  UPDATE A reader, David Dixon, reported the following:-
  In this area I have heard nothing but praise for Teakdecking Systems 1-part silicone based caulk. Contact onfo: http://www.teakdecking.com/index.html. Not only are the local boatyards (San Francisco area) using it but the SF Maritime Museum has used it on it's historic vessels, including the Balcutha, with good results. I have done seam repairs that still look great after 4-5 years. In my experience it is much better than 3M 101 - more flexable and resistant to UV and chemical deterioration.
• It is nice to have a tube or two of the 3M 101 sealant on hand (about $11 ea) for touch ups and small repair jobs where you don't want to mix up a quart. They only last about 12 months in cool storage and must be used or discarded once started. It is not as good as the 2 part mix but much easier to prepare, especially for small touch up jobs.
  UPDATE, A reader reported to me that a few years ago 3M introduced a product called Teak/Wood Seam Sealer and since its introduction 3M no longer recommends using 101 for deck seams.
• Empty cartridges with plungers to put the liquid sealant in. ($0.70 to $0.99 each depending on supplier and quantity, available from Jamestown Distributors, West Marine and others.) You will need two for each quart of sealant.
• Masking tape. If the weather is cool and you will be done fairly quickly (48 hours), use the SCOTCH Long Mask Blue, #2090 in 1 inch width (about $3.00 per roll of 180 feet). If it is hot or the job may be left sitting for a while, use the SCOTCH Silver Weather Resistant Tape, #225 in 1" width (about $11 per roll). You will need about 4 feet for every isolated foot of groove or 2 feet for every foot of groove where they are adjacent.
• Single Edge Industrial Razor blades. (About $3.80 per box of 100.)
• Disposable Latex Gloves (about $13.00 box of 100). Get one size larger than you think you need. (West Marine, Jamestown Distributors)
• Protective goggles or shatterproof glasses - essential when using the power tools on teak. Compromise on safety a little and avoid the ones that don't have ventilation - they will be too hot and uncomfortable to use.
• Single edge plastic spreaders, 2½" wide (about $24 box of 100 at Jamestown Distributors). They are re-useable but you have to let them set up before you can clean them so you need quite a lot.
• Unlimited supplies of paper towels.
• Wooden paint stirrers ($0.10 each).
• Wooden tongue depressors ($6.00 box of 500).
• Old clothes - believe me you WILL get black s**t on them.
• A big cardboard box, at least 2½ feet per side minimum to make a work area.
• Long nail or awl to prick the foil sealing the cartridges.

Supplies and tools you DON'T need.

• You do not need extra hardner for the polysulfide.
• You do not need primers unless it is new teak and even then I am doubtful that they help. (I have tried with and without and different primers and had more trouble than just the plain un-primed teak.)
• Calking cotton and caulking tools.
• Power mixer for the polysulfide. (They make a bloody mess and they infuse air into the mix, plus they are an invitation for total utter end of the world disaster if the can gets loose. Mixing a quart at a time by hand only takes about 5 minutes.)
• Don't be tempted to use ordinary paper masking tape.
• A router is too difficult to control by hand and too time consuming to use with guide bars - the miniature skill saw is much better.

STAGE 1, Removing the old caulking.

Timing the job with the weather is important. Caulking can only be done when the deck is thoroughly dry and has been thoroughly dry for at least a week, because that is how long it takes for the wood to shrink. If you calk when the deck is at maximum shrink, then all it can do is expand and press on the caulking. If there is any moisture and the teak is not at maximum shrink when you caulk, then when it eventually dries out, and it will, the caulking will be in tension and you risk it pulling off the sides of the groove. Ideal conditions are not always possible but at least you know what is ideal.

Go to stage 3 and read the first paragraph then come back here - there is something you need to have prepared 6 hours in advance.

Keep in mind as you establish the area you are going to re-caulk that you have to be able to reach every part of the work area from outside the perimeter later on when you are placing and smoothing the polysulfide. Don't "paint yourself into a corner". If the deck has some slope in the direction of the seams, you need to do shorter runs so that the polysulfide does not run down to the lowest spot and cause a problem (or use the thicker grade of polysulfide but it is much harder to work). You might need to do every alternate 1 or 2 foot strip, then come back next time and do the pieces in between, using some of the old caulking to make a dam. Identify the areas you intend to caulk and mark with a piece of chalk, or masking tape.

Don't tackle too large an area. Each quart does an area about 2 feet by 10 feet (2" planks) but this varies considerably with groove width and depth. There are various formulas around for calculating total running feet but they are only a very rough guide due to all the variables. If you choose too small an area, you will have caulking compound left over at $25 qt. If you choose too large an area, even though you plan to mix up multiple quarts, you may not be able to do it all in one session. Leaving the masking tape on deck overnight usually results in some of it lifting off due to moisture. Murphy's law dictates that no matter what area you do, it will require just a little bit more caulking compound than you mixed up. So leave the remainder for the next sesstion or touch up later with some 3M 101.

Use the scraping tool to dig into a good section and draw towards the loose (leaking) caulk to be removed. Separate each side then pull it out. Don't throw it overboard - it will never degrade - drop it in one of those pails. Needless to say, be very careful not to slip out of the groove and scrape a nasty scratch in the teak. Don't panic if you do - just don't look at it. After about 3 months it will go away with swelling from moisture, fading from sunlight and erosion of the scratch edges.

Use the scraping tool to clean any loose stuff from the groove edges and bottom. Use the vacuum frequently to clean it out. If there are any soft spots in the teak, they have to come out. Use the Dremel tool if necessary. The groove will no longer be straight edged but the caulk will fill in the void. Don't be tempted because of cosmetics, to leave a piece of spongy teak. It will only collect water and get worse. Yes teak does rot, believe it or not. I think some sections of the wood are more prone to rot than others depending on where they were in the tree.

If the groove runs up to, or under a deck fixture, use the Dremel tool to dig out right up to the fixture and under-cut the fixture as far as possible.

Inspect the groove. If the width is too narrow, or the depth too shallow, or the sides soft and fragile - then you need to re-groove (see the earlier discussion on optimum width and depth). This is where you use the mini skill saw. Do it by eye. Set the depth to the desired groove depth. Run down one side, then turn around and go back up the other side, removing a little teak from the sides to provide a good foundation for the new caulking. If you are making it deeper you may need to do some runs in the center to remove the remaining material. Where you can't get in because of deck fixtures and for those seams on the end grain, use the Dremel tool.

In particularly bad spots, where you really should replace a piece of plank but don't want to tackle it, I have used an epoxy paste to repair the wood. It will only be partially successful because the epoxy will eventually crack off the teak as it moves, the epoxy deteriorates in sunlight, and the rot will continue despite all attempts at repair. I have had best luck with the West System epoxy thickened with teak sanding dust or #405 filleting blend.

Stage 2, Masking.

This is pretty straightforward. You need to be fairly precise but not too finicky. If a little polysulfide ends up on the top of the teak, it will be so thin that after it sets it can be rolled off. If the tape sticks over the groove in a spot, the polysulfide will run under it. Use a razor blade to trim around the detail spots. Roll or rub the edges down to make sure they are stuck well. Avoid pieces of tape turning the corner over the edge and projecting down into the groove.

There must be at least 2 inches of masked area each side of any place to be filled. If the planks are 2" wide and you have adjacent grooves to be caulked that works out fine, if not you need to put an extra piece of tape to make up the width. Don't forget to tape the edges of deck fixtures.

When masking is completed, take some more masking tape and tape it around outside the perimeter. Later on, after you pull up the tape but the caulking is still wet, it will be very difficult to know what is wet and what is not so the perimeter outlines will help you avoid stepping on them until they set.

Stage 3, Preparing the Polysulfide.

The manufacturer(s) claim a 3 hour work period once the polysulfide is mixed. Don't believe them. The trick is to put the (unopened) polysulfide cans with their hardener in the refrigerator at least 6 hours before use so they are at about 40 degrees when you go to mix them. Even then, you will only get about an hour of good working time. One good reason for doing a quart at a time instead of struggling to use up a gallon mix before it sets up. Return to stage 1

Do this work on the dock if you can, it is very dangerous as any spill will be a total catastrophe and a dock disaster is better than a boat disaster. Take that cardboard box and cut an opening in it to make a work area. Leave about a 12 inch wall on the front and angle up 45 degrees on both sides to the top. Do all the mixing in the box.

Put on rubber gloves right now. Don't be tempted to do any of this without them, the moment that black stuff sees any exposed skin it will jump up to 3 feet and get on you before you even see it. As soon as a glove gets icky, peel it off, drop it in a pail and put on a fresh one.

Have tongue depressors handy for scraping. Have lots of paper towels ready. Turn the can of polysulfide upside down and remove the bottom with the can opener. Trying to work through the paint can type lid and to pour from it is impossible. They leave about 3 inches of space in the can to let you mix without spilling. Open the hardner can. Lately they have been a plastic screw-off lid which is easy. Some may still come in a mini paint can so again, open the bottom with the can opener, there is no way you can scrape the contents out from under the lip if you remove the normal lid.

Scrape out all the hardener into the can of polysulfide. Never try to do a partial mix, always mix the whole quart with all the hardener, even if you only have a small job to do. It would help if they made the hardener a white color so you could see how well the mixing is going but with the colors nearly identical you have to judge when mixing is done. Use a paint stirrer stick (never a power tool) and stir it in. Use plenty of up/down motion to work it through and repeatedly scrape the bottom corners. Avoid trapping air bubbles in the mix. We need to get the hardener dispersed so throughly that every molecule of polysulfide is in contact with a molecule of hardener so there are no soft gooey spots which don't set up. It takes at least 5 minutes of dedicated stirring - you can't over do it but you sure can have a mess later if you didn't stir enough.

Squeeze the can opening at one side to make a pour spout. Pour the mix down the center of the cartridges so it builds up from the bottom without trapping any air. You still have the gloves on don't you? And work in the box where the drips won't do any damage. Wiggle the plunger in until all air has been allowed to escape. Air bubbles and pockets cause two problems, one is voids in the caulk seam which either stay there of have to be filled if they rise and pop, the other is they compress under pressure in the caulking gun and expand every time you try to stop caulking forcing liquid to continue to come out when you least expect it.

Put one of the cartridges in the freezer to help stop it setting up while you use the other. Keep them out of the sun and as cool as possible.

Stage 4, Caulking (finally)

If you haven't already read section 5, read it before you start caulking so you are familiar with timing.

Fresh pair of gloves on. Have a stack of plastic spreaders handy. Lots of paper towels handy. Extra gloves handy. Pail for dirty towels, etc. Lock the cat below deck. Unplug the telephone. Hat and sunglasses on before the gloves get dirty.

Place cartridge in the gun. BEFORE trimming the end and piercing the foil seal, pump the trigger on the gun and pressurize the plunger quite hard. This will force out any air bubbles trapped between the plunger and the liquid. Air bubbles are a nuisance because they continue to expand after you release the pressure and cause the cartridge to dribble all over the place.

RELEASE the pressure and trim off the end of the nozzle to leave a 45 degree hole about 3/16 inch diameter. Use a long nail or awl to prick the foil seal inside. Squeeze the stuff into the grooves. Work about 2 or 3 feet at a time, then squeegee the surface flush as necessary with the spreaders. As they get icky, discard them in an appropriate container for recovery later and take a fresh one. It is OK to scrape up the excess from one area and trowel it into an area that didn't fill. Check back as you go, for bubbles that need pricking and perhaps re-filling. If an area has a slope and it is tending to run down leaving one area low as it runs out the other end, come back to it later as it starts to thicken. If necessary, just let it set partially full, you can repair it during a subsequent caulking session or even use some of the 3M 101 to patch it.

Stage 5, Removing the masking tape.

Removing the tape is much more critical than it would first appear. If you remove it too early, it will pull stringy bits off the groove which will fall onto the deck, and mess up the teak and nice caulk surface. If you remove it too late, the tape will be embedded in the caulk and become a mess to be trimmed with a razor later when it is fully set.

Have the pail(s) ready to catch the icky tape which will be flapping in the breeze and threatening to get over the white salon top.

Under normal circumstances you need to remove the tape one hour after you did the caulking. Normal circumstances mean a mild temperature (70 degrees F) with no sun on it. It will then take about another two or three hours before the surface is no longer tacky and about 24 hours before it is safe to walk on.

BUT every 10 degrees hotter, halves the time frame and every 10 degrees colder doubles it. So if you are in the noonday sun with no shade, and the deck is running 120 degrees, that is 50 degrees hotter so you halve the 60 minutes 5 times. So one hour to removing the tape becomes 30, 15, 7.5, 3.75, 1.875 or 1 minute and 52 seconds. This is an extreme case but I have done caulking under these conditions and about the time you squeegee one section flat, it is time to pull up the tape. It is fully set and ready to walk on in an hour. The opposite is the case if it is colder. You should not try caulking below 50 degrees and the time to removing the tape would be 4 hours with maybe 2 days before it is safe to walk on. In all cases, a little testing is a good idea to time tape removal.

Please send me your comments, criticism, encouragements and particularly any ticks you learn that I should include in this guide for others. When I do my next job I will remember to take pictures and add them to this work.

Andina Foster,

tech@yandina.com