One problem we had known about for some time was around the hatch on the back deck -- it moved up and down when you stepped on it. Not supposed to happen. As 2016 came to a close we could put it off no longer. It was time to pull up the teak and deal with it.
Compadre's teak decks, and some of the underlying beams, were replaced about 15 years ago and generally are in good condition. Beneath the half-inch teak boards is 3/4-inch marine plywood resting on fir beams. Around the hatch in the back deck, water had leaked inside the hatch opening, and then seeped between the teak and the underlying plywood, causing an area of rot extending a foot or so in all directions. The teak was fine, but the plywood and underlying beams were rotted and needed to be replaced. This was going to be a big job, but one I felt I could do myself. The first step was to pull up a few teak deck planks to investigate.
|Beginning to take up the teak deck. Hatch is in the foreground, looking aft.|
|Directly beneath the teak was waterproof membrane. Nicely done.|
So with all this fancy waterproofing, why did we have a rot problem? In spite of using good materials, the installer forgot one important thing: Flashing around the hatch opening. The teak and plywood simply ended at the hatch opening, with the raw edges covered by some teak trim. A little rubber seam compound between the trim and the teak deck boards was the only thing keeping the water out. I'm sure it didn't take long for rain water to begin to find it's way behind the seam compound and back under the fancy waterproof membrane. Eventually an area about 1-foot wide on each side of the hatch was saturated by water and rot soon followed. Some simple flashing around the opening, as is typically done around house windows, would keep this from happening again, but first we had some work to do.
|Removing rotted plywood underlayment.|
|Hatch framing and deck beams also were rotted.|
|Finally, all rotted plywood removed.|
|Hatch framing removed and existing beams tapered. Ready for new wood.|
|Replacement deck beams in place.|
|New hatch framing.|
|Detail of hatch-frame joint|
|Cutting saw kerfs on the underside of replacement plywood.|
|Self-adhering flexible flashing at the corner.|
|Self adhering flashing all around.|
|Ready for metal flashing.|
I was confident that the self-adhering flexible flashing would prevent any water from contacting the wood, but it is not durable enough to stand on it's own in a high-traffic area such as the deck hatch. It would need some protection, and for that I chose metal roof flashing. This is sheet steel, so there is some risk of rust, but I planned to paint any exposed metal with marine enamel for extra protection.
|First piece of sheet metal flashing.|
|Flashing corner detail.|
|This is not going to leak again.|
Next came the new waterproof membrane. This has a peel-off adhesive backing, and firmly attaches to the old membrane around the edges of my patch, and to the new decking and flashing.
|New waterproof membrane atop the plywood and flashing. Ready for teak.|
|Teak back in place. Installing bungs in screw holes.|
A thin strip of teak trim around the edge of the hatch covers most of the metal flashing. In spite of all the rot in the fir deck beams and plywood, the original teak trim was still good. Amazing stuff, that teak.
|Finished, and good as new -- maybe better?|