My wife and I feel that a teak deck is by far the most superior deck material there is. It's traction properties are outstanding, wet or dry. And it looks good if it's in good shape and is properly cared for. So we have spent a lot of time learning how to care for the deck on our boat.
In our opinion, there are only three reasons to get rid of a teak deck.
1. The teak itself is so worn out, weathered, or abused that it's simply not serviceable anymore.
2. The owner does not want to spend the time doing what is necessary to properly maintain a teak deck.
3. The owner simply doesn't like a teak deck. (It gets very hot in hot climates, for example.)
Our 41-year-old boat still has its original teak deck. When we bought the boat in 1998 the deck had been over-sanded by previous owners, or perhaps they had used teak cleaner/restorer which does exactly the same thing as sanding only it does it chemically. EIther way, wood that goes away does not come back. So the boards were getting thin.
But an experienced shipwright determined there was still enough thickness to be serviceable, so we had the main deck re-grooved and re-seamed and I reset hundreds of deck screws and replaced hundreds of plugs. (The teak deck on the flying bridge is always under cover, so it is in like-new condition.)
The reseaming was done with the established seam sealant at the time. It was too bad that it was done before a far superior sealant, TDS seam sealant, came onto the market.
In more recent years I have re-seamed various grooves as the traditional sealant that was used for the re-seam job in 2000 or thereabouts deteriorated or pulled loose from one side of the seam or the other, the most common problem that admits water under the boards. By now TDS was readily available---- my first two tubes were sent to me by TDS when I called them asking about something else--- so all our re-seaming work is done with that material. So far as we're concerned, it's the only sealant worth using on a teak deck, and is what Grand Banks, Fleming, etc. use at their manufacturing plants.
Today, I need to replace a number of seams on the foredeck that have started to deteriorate and a number of the older, thin plugs have come off and need replaceing after I reset the screws. But the processes of seaming, and reseting screws and plugs, while time-consuming, are simple and straightforward once you know how to do them. I find it rather enjoyable to work on the deck. The challenge for us is that our boat lives outside and we have limited time due to my work schedule. So wer really have just weekends.
The deck has to be absolutly dry as a bone before doing any re-seaming work, so the combination of my schedule and the weather up here conspire to prevent us from working on the deck when we'd like to. In a couple of years I'll have more time so we can really tackle the job correctly, assuming we still have this particular boat.
The biggest culprit in a leaking deck tends to be one or more seams that have pulled away from one (or both) sides of the groove. This can be hard to see and requires a close examination of the seams. Once discovered, teh separated section of seam is easily dealth with by remving the old sealant and replacing it with new.
There are a two of techniques for doing correctly; done wrong, the repair will not be very long-lived.
If one elects to replace the seam altogehter, it's very important to use bond-breaking tape in the bottom of the groove, for example, so one needs to learn what it is, where to get it, and how to use it. Some people claim the tape is unnecessary. But everyone I've met or corresponded with who has a lot of experience in dealing with teak decks uses the tape. And when one understands why and what happens if the tape is not there, it become pretty obvious why one should use it.
There is a ton of material on how to repair and maintain teak decks on the Grand Banks owners forum, which makes sense since almost all GBs were built with teak decks and most of them still have them. Searching the archives on that forum will yield all sorts of useful information. I think you have to join the forum to search the archives, but it's free. Grand Banks Owner's Resources
Some of that information has been posted here over the years, but I think the GB forum will yield far more information.
If one decides to remove a teak deck and replace it with fiberglass, they need to know what a big job this really is. It's not a matter of just putting some glass over the teak, although there are people who have done that. It's a bad idea for a bunch of reasons, so I would never recommend that anyone go that route.
I watched a fellow on our dock replace the teak deck on his Island Gypsy a few years ago. He did it a beautiful job--- actually he overdid it in terms of the layers of fiberglass he put down to restore the stiffness lost when the teak is removed from a deck--- and his deck is now strong enough to land a plane on.
It took him a summer and a half of working most days of the week to do the job, and when he was done he told me that had he known how much of a job it really was he never would have started it. But he did a better job than probably the factory would have done had they made the boat without a teak deck.
So one shouldn't view the notion of pulling up the teak and putting down some fiberglass as an easy task. Not if one wants to retain the boat's value, at any rate.
The stop-gap methods often bandied about for "repairing" a teak deck--- fiberglass on top, truck bed liner on top, etc., will work for awhile. But they will fail sooner rather than later because the wood underneath them is not inert and as it moves and swells and shrinks with humitdy and simply being walked on, the quick-fix surface will begin to separate and crack adn moisture will begin to get underneath. Eventually, the owner will face a much larger repair job than he or she had before the quick-fix was applied.
I've seen boats, power and sail, in our marina--- some on our dock--- that have had these quick-fix treatments applied to a failing teak deck. They were okay for a few years. Then the problems started, and in the end, the owners were facing a huge repair task.
So better to do the job correctly to start with. Either fix the teak deck properly, or replace it properly.
Photo is our 41-year old deck today.