Re: Teak Decks
15-20 years is about the extreme limit for the lifetime of a screwed down teak deck.
What happens is that the screws, due to thermal cycling of the deck begin to 'saw' themselves loose, and if the 'thiokol' also begins to separate between the teak straking and the FRG deck ... you ARE going to have leaks.
NOTHING has the wet-traction of teak decks.
The repair, if done 'carefully' so that the underdeck can be restored/recored, and the teak straking remilled and 'epoxied' back to the deck will restore back to OEM condition .... you just 'remill' the 3/8" bung holes (no screws) to a large diameter - 1/2". This can be a back-breaking job, requiring care in removing the old teak (if its still thick enough) if you plan on re-using it., the use of an AIR CHISEL to remove the affected core, replacement with new core, re-lamination of the upper FRG surface, etc. etc. .... and NO screws into the FRG undelayment.
If youre looking at an old teak deck, try to find one that was 'cared for', and has been covered with a 'sealer' (Semco, etc.) that has prevented the usual 'surface erosion' and thinning of the thickness.
When assaying, wear hard leather or hard rubber soled shoes, and bear weight on each strake .... when you push down, simply watch/feel for movement of the strake indicating that the screws have 'sawn themselves' loose. The least total amount of movement under foot pressure usually indicates the minimal amount of core removal .... you only have to do 'area repair' instead of the whole damn deck.