..an expoxy sealed ply substrate. Much greater life expectancy and overall a more stable performer. I also have to say if it will be varnished or left bare makes a difference. If I'm gonna varnish the finished product, I'd MUCH rather use Honduras Mahogany than teak or any other multo oily wood (slipped a little Italian in there, eh?) regardless.

An example of this work done by myself and which was able to be observed at intervals of years over thirty years would be the hatches I built for Passage in 1979. I used 1/4" ply and epoxied 1/4" H. Mahog onto that. In laying in the grooves later filled with carbon filled epoxy I actually used a router and a straight edge on some, rabbetted with a table saw others depending on where I wanted the lines to lay. After thirty years under varnish and also years left without, the hatches are still in use today in the boat being rebuilt after a PO let it sit for fifteen years anattended. The carbon filled epoxy is STILL intact perfectly.

You could poke your finger through the 3/4" thick H. Mahog cabin side in a couple places but the hatches...still solid.

An example where that DID NOT WORK was in the 1/8" teak veneer deck I laid onto the ply substrate for the deck about three years after I built the boat and did a rebuild of the vee berth area and did the deck. I followed the Gougeon Bros.' instructions, epoxied on the 1/8" by 2" wide VG strips I'd ripped. I laid them in carbon filled epoxy with 1/8" grooves which allowed "mooshing" of the black epoxy stapled with bronze staples, etc. Acetoned surfaces, etc. What FAILED in the deck was the adhesion among the 1/8" carbon filled stripes of the epoxy on the shallow edges. Expansion and contraction of the TEAK weakened the epoxy adhesion over time. It turned out the sun was the enemy creating such heat that the thin epoxy areas could not hold in the TEAK. I read a few years ago in Epoxyworks mag by Gougeons that they were aware of this and were less likely to do this now. Live and learn.

(Originally the deck had been 'glass cloth laid in Aerobal over epoxied 1/2" [two 1/4"] ply which the cabin top was for the thirty years with no problems).

To make a short story long, I'd use H. Mahog which is MUCH better suited than teak AND I'd lay it up in thin'ish strips using carbon filled epoxy for varnish. If you intend to use teak and let it go gray, it's kinda all bets are off in the long run. IF I was gonna use teak, I think I'd go with proper black caulk for this SPECIFIC purpose for the black seams.

I confess I frequently do the thinner wood on ply thing and put trim pieces epoxied onto the ply edges and overlapping the "beauty" wood teak or H. Mahog and it looks to my untrained eye like solid wood.