How to recaulk a superyacht deck

Carpentry and joinery is an extremely important part of any boat, especially a superyacht, and there are many different jobs a carpenter will be required for on board. The deck is the first thing you see past the passerelle and where most of your time is spent on sunny days. Below, leading yacht carpentry and repair company Woodstock Boatbuilders, explained how one of the most important issues is the impending recaulking of a superyacht deck.

Recaulking a teak deck

There comes a time in the life of any teak deck when recaulking is required. There are several reasons why it may be necessary to remove the existing caulking from the seams and replace it.

According to Andrew Robinson of Woodstock Boatbuilders, “It may simply be that the deck has worn to such an extent that the caulk in the seams is too shallow to be effective. Another reason may be that the caulk itself has broken down (a chemical failure) and is no longer doing its job. Another reason could be that the caulk has let go from one or both sides of the seam, (physical failure), again failing in its main role of keeping the water on the outside.”

Why are decks caulked in the first place?

Yacht decks get about the most punishment of any part of the yacht’s superstructure. Woodstock Boatbuilders have suggested three possible reasons why the deck may need recaulking:

1. Foot traffic: All of the wear and tear from foot traffic on board the yacht
2. Exposure: Being more or less horizontal, decks are subjected to maximum UV rays from the sun, which can be very harmful to the caulk
3. Constant wetting and drying: This causes continual expansion and contraction of the deck planks, which puts strain on the bond between the caulk seam and the planks. It's for this reason that a very stable wood, usually teak, is used for the planking

How to know if the deck needs recaulking

Some common tell-tale signs that the deck needs recaulking are:

Chemical failures

• Crocodile skin: This is where the upper surface of the caulking is often dried and shrivelled and underneath is soft and gooey. The result looks like the skin of a crocodile; uneven and rough
• Black smudges over the pristine teak deck: The caulking looks fine, and is generally doing a good job, however it becomes somewhat water soluble and softens on its upper surface, as people walk around, the caulk is picked up and can get everywhere. Test the caulking when wet, rub your finger on it and see if it dissolves
• Complete chemical breakdown of the caulk: This is the same as above but the caulk is obviously soft and gooey

Physical failures

• The deck leaks: Not always the fault of the caulking but often is
• Sidewall adhesion issues: Due to poor adhesion and continual expansion/contraction of the deck planks, the caulk lets go of one or both sides of the deck seam. This can be a combination of shrinking caulking and poor adhesion
• The caulking has let go of all three surfaces (bottom and two sides of the seam) and come out of the seam - often the result when the teak wears thin and the caulk is in a shallow seam
• Voids and other issues involving poor installation

What to do if you suspect your deck needs recaulking

For the final step, Andrew Robinson of Woodstock Boatbuilders has advised four steps that should be followed when recaulking a deck; this will ensure the process runs as smoothly as possible and the best possible results are achieved.

Contact an experienced professional

Whilst recaulking a teak deck may look simple it can lead to a very big mess if carried out by inexperienced persons. The human eye is capable of discerning very small differences in the width of a teak deck seam. It is critical, that when removing the old caulk, the seam width is not enlarged discernibly. Often seams are intentionally deepened when recaulking, which can require the use of an electric hand tool to speed up the process. A router in the wrong hands can be a very destructive tool.

Mind the mess

Another obvious pitfall is the mess caused by spreading the newly opened caulk over otherwise pristine surfaces, and not just the teak deck. There is that old adage about a popular caulk that was so named because it had the uncanny habit of spreading itself from a newly opened cartridge on the foredeck, to fifty four hundred other places all the way back to the transom! Well it's not just the above mentioned caulk that can create an unholy mess; any cartridge of caulk can spread itself very thinly over a large area of a yacht, covering areas that should remain un-caulked.

Planning is paramount

Once a trustworthy and experienced professional has been sourced, the next stage is to plan the recaulking project. As they say, you can't make an omelette without breaking an egg or two. Recaulking is messy, it's the nature of the beast, but that doesn't mean the mess has to get out of hand. However, you may want to situate the yacht in a position where you're not upwind of your neighbour who's preparing to lay on that last coat of varnish over the cabin sides or caprail. An experienced recaulking crew will show up with rubbish bags to contain and dispose of the old caulk, as well as tools hooked up to a vacuum cleaner, in this way the mess is minimal. Prepare the working environment, put away as much as possible from the deck.

“Here at Woodstock Boatbuilders we have a mantra; the three most important aspects of carrying out a project are: protection, protection and protection. It should be self-explanatory, don't damage any aspect of the yacht whilst working aboard. By now you should have established which deck hardware is to be worked around and which, is to be lifted and refitted after recaulking final sanding. Lifting hardware may involve removal of headliners below decks to access fastenings. Tape up hatches, teak/caulk dust from a router can be very tenacious when it comes to finding its way into the interior through closed hatches, don't forget dorades and engine room air intakes need dealing with in such a way that you don't overheat crew or machinery.”

Choose the right caulk

So now the seams are cleaned and possibly deepened, and you're ready to apply the caulk; now for the million dollar question, which caulk to use? Every boat builder will have their favourite, but now is not the time to try and save a couple of dollars, buy the best caulk available, there have been several tests carried out and the same two or three always come out on top.

The finishing touches

Finally the deck will be sanded, hardware replaced, cushions back out on deck and your once tired, maybe leaking teak deck will be looking and feeling like a million bucks, and will serve you well into the future and will have added considerable value to the yacht.