Teak Deck Caulking
One of our members experienced the following: For the seam caulking we used Mapei Silwood Decking. As the boat is berthed near a boatyard, we thought we would protect the finished deck by applying a sealant – we were recommended a product known as Teak Wonder. Everything seemed alright for the first two to three months, but we then noticed that the rubber caulking seemed to be crystallising and separating, from the wood. I asked Teak Decking a highly reputable teak deck supplier and fitter to comment as follows:
There are so many possible factors that may be the cause, or simply contributing. If the caulking had simply separated from the teak, it would be easy to assign it to bad preparation/application (..and possibly bad material). However, since the material changed properties – crystallizing – something else is probably going on. The only way that I can think of to determine if a chemical reaction between the caulk and sealer has taken place would be to try and duplicate the result with test samples. I would make up a sample with the same batches of caulking and sealer used on the boat, another sample with a different batch of caulk and the original sealer, another sample with the original batch of caulking and new sealer, and a final sample with new caulk & sealer. I would also create samples with new and original batches of caulking, with no sealer. If none of these test samples show the same result as the deck problems after being in the same climatic conditions for the same time period, the problem is something else. For instance, we have seen some of the northern European caulks react badly to tropical heat and/or cleaning products. So, a thorough investigation should include determining what other chemicals (beside the sealer) have been applied to the decks. This determination can be tricky because no one wants to be to blame, including the owner. All it takes is one application of the wrong chemical to create a situation that may take weeks or months to manifest. So, anyone (shipwright, shipyard, captain, owner…) who applied anything to the deck other than water needs to be forthcoming about what they did, and used. Someone may have had the idea to ‘brighten’ the teak, using an unsuitable product.
Reviewing the caulk manufacturer’s web site, I got no indication that the product is intended for boats. I suspect that in formulating the product, they gave no consideration to the product being in contact with the aggressive cleaning chemicals used by captains and owners, or of it even being used on boats. Resistance to chemicals is a major consideration in the formulation of our SIS 440 Teak Deck Caulking.
As you can see, unless someone comes forward to admit that they screwed up, or the product manufacturers admit to a bad batch (not likely) determining the cause will be difficult. At some point the conversation will have to move to how do we fix it and move on. Obviously, the first step will be to remove the old caulking and thoroughly clean the seams. Before installing new caulking, the teak needs to be thoroughly dry, which means that the decks need a couple of weeks out of the rain (wood does not dry out overnight). The teak in the seams needs to be degreased to remove surface oils within an hour or two of applying the caulking. If too much time passes, new oil will work its way to the surface of the wood. Since I am not familiar with the caulking product used, I cannot comment on whether it should be used again. Given the problems, unless there is a huge financial concession from the caulk supplier, I would re-caulk with our SIS 440 caulking. First of all, it has been formulated specifically for caulking teak decks. It is not a relabeled industrial caulk. Each year we build the equivalent of 250-300 Swan 46 teak decks. With that kind of volume, we cannot afford to have problems with our caulking. I’ve worked at Teakdecking Systems on and off for around 20 years. In that time I have never encountered a SIS 440 caulking problem that wasn’t caused by either improper application or the use of improper chemicals during cleaning. So, I have a lot of faith in the product.
One little detail that we employ in the building of our decks to reduce the likelihood of the caulking separating from the teak is to apply a bond breaker tape to the bottom of the caulk seams. This tape prevents the caulking from bonding to the bottom of the seam; which allows the caulking to expand and contract like an accordion when the wood swells or contracts. If the caulk is stuck to the bottom of the seams as well as the sides, stresses build up in the corners as the wood moves around. If the caulk cannot flex enough at the stress points, it will separate, either from itself or the sides or bottom of the seam. Our solution is to avoid the stress in the first place…and use a caulk created for bonding to oily teak wood.
By the way, we are not a big fan of sealers, teak oils, etc. We recommend simply cleaning the decks with a good 1-part teak cleaner and an occasional light sanding to reduce the rough profile created by natural weathering of the surface over time.
With kindest regards,
Teakdecking Systems
Peter Wormwood
Yacht Services
7061 15th Street East, Sarasota, FL 34243
Fax: +1 941 756 0406 Tel: +1 941 756 0600 ext. 228
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I wish that I had a clear cut, succinct answer to the problem that your fellow 46 owner is experiencing with the caulking in his decks. There are so many possible factors that may be the cause, or simply contributing. If the caulking had simply separated from the teak, it would be easy to assign it to bad preparation/application (..and possibly bad material). However, since the material changed properties – crystallizing – something else is probably going on. The only way that I can think of to determine if a chemical reaction between the caulk and sealer has taken place would be to try and duplicate the result with test samples. I would make up a sample with the same batches of caulking and sealer used on the boat, another sample with a different batch of caulk and the original sealer, another sample with the original batch of caulking and new sealer, and a final sample with new caulk & sealer. I would also create samples with new and original batches of caulking, with no sealer. If none of these test samples show the same result as the deck problems after being in the same climatic conditions for the same time period, the problem is something else. For instance, we have seen some of the northern European caulks react badly to tropical heat and/or cleaning products. So, a thorough investigation should include determining what other chemicals (beside the sealer) have been applied to the decks. This determination can be tricky because no one wants to be to blame, including the owner. All it takes is one application of the wrong chemical to create a situation that may take weeks or months to manifest. So, anyone (shipwright, shipyard, captain, owner…) who applied anything to the deck other than water needs to be forthcoming about what they did, and used. Someone may have had the idea to ‘brighten’ the teak, using an unsuitable product.
Reviewing the caulk manufacturer’s web site, I got no indication that the product is intended for boats. I suspect that in formulating the product, they gave no consideration to the product being in contact with the aggressive cleaning chemicals used by captains and owners, or of it even being used on boats. Resistance to chemicals is a major consideration in the formulation of our SIS 440 Teak Deck Caulking.
As you can see, unless someone comes forward to admit that they screwed up, or the product manufacturers admit to a bad batch (not likely) determining the cause will be difficult. At some point the conversation will have to move to how do we fix it and move on. Obviously, the first step will be to remove the old caulking and thoroughly clean the seams. Before installing new caulking, the teak needs to be thoroughly dry, which means that the decks need a couple of weeks out of the rain (wood does not dry out overnight). The teak in the seams needs to be degreased to remove surface oils within an hour or two of applying the caulking. If too much time passes, new oil will work its way to the surface of the wood. Since I am not familiar with the caulking product used, I cannot comment on whether it should be used again. Given the problems, unless there is a huge financial concession from the caulk supplier, I would re-caulk with our SIS 440 caulking. First of all, it has been formulated specifically for caulking teak decks. It is not a relabeled industrial caulk. Each year we build the equivalent of 250-300 Swan 46 teak decks. With that kind of volume, we cannot afford to have problems with our caulking. I’ve worked at Teakdecking Systems on and off for around 20 years. In that time I have never encountered a SIS 440 caulking problem that wasn’t caused by either improper application or the use of improper chemicals during cleaning. So, I have a lot of faith in the product.
One little detail that we employ in the building of our decks to reduce the likelihood of the caulking separating from the teak is to apply a bond breaker tape to the bottom of the caulk seams. This tape prevents the caulking from bonding to the bottom of the seam; which allows the caulking to expand and contract like an accordion when the wood swells or contracts. If the caulk is stuck to the bottom of the seams as well as the sides, stresses build up in the corners as the wood moves around. If the caulk cannot flex enough at the stress points, it will separate, either from itself or the sides or bottom of the seam. Our solution is to avoid the stress in the first place…and use a caulk created for bonding to oily teak wood.
By the way, we are not a big fan of sealers, teak oils, etc. We recommend simply cleaning the decks with a good 1-part teak cleaner and an occasional light sanding to reduce the rough profile created by natural weathering of the surface over time.
With kindest regards,
Teakdecking Systems
Peter Wormwood
Yacht Services
7061 15th Street East, Sarasota, FL 34243
Fax: +1 941 756 0406 Tel: +1 941 756 0600 ext. 228
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I had a new teak deck put on – best cured Burma Teak – shaped exactly as old deck with a thickness of 15mm. For the seam caulking we used Mapei Silwood Decking. As the boat is berthed near a boatyard, we thought we would protect the finished deck by applying a sealant – we were recommended a product known as Teak Wonder. Everything seemed alright for the first two to three months, but we then noticed that the rubber caulking seemed to be crystallising and separating, from the wood. The work was carried out by a professional shipwright with experience in laying on new teak decks – he had used the Mapei Caulking before with no problem – he had not however used the sealant Teak Wonder. To cut a long story short, we have had to remove all the rubber caulking and re-caulk again. We are in correspondence with the manufacturers of Teak Wonder and of Mapei – they both say that their products have been used extensively and that they have not encountered the problem that we have had. We have just finished the new caulking and are hesitant about applying a sealant – it is said that the best treatment for teak decks is sea water!
I would very much welcome the views of fellow owners, first of all to ascertain what products you have used when laying on new teak decks, for caulking and for sealing – has anyone used Mapei Silwood Decking or Teak Wonder? What should have been a fairly routine job has turned out to be an expensive nightmare! I am still battling to get to the bottom of the problem.
