Deck repair

Looking for some advice on this deck repair (photos of the affected area attached). It’s teak glued onto marine plywood. There is no visible damage to the teak or the caulking. However, the plywood underneath is delaminating.

I suppose the safest approach is to remove the teak and cut out the damaged ply and replace it with new. I’ve never done a job like this, so not sure of the risks and techniques to use to avoid damaging the teak.

Alternatively, is it possible to repair from underneath by removing the plywood and gluing in a new section? That would not help with fixing the source of the problem (as I assume it’s water infiltration from above, though I don’t know where from exactly), but it would at least spare some risk to the teak. Never done a job like that either, so any advice on techniques to use would be much appreciated. Access to the ply underneath is not great (it’s the inside of a galley cabinet).

 

Well, thanks for the pictures.
I’m a little curious how you suspect water ingress. Is this area completely outside or partially outside or subject to rain or splash?

Always with boats, determining the source of ingress is first.

If the teak is glued down; it is possible the entire panel may come up, ply and all. Very hard to tell from the pics if that is even possible, but it would be ideal.

If the entire thing delams, you could repair the rot and bond the entire thing back down to the remaining ply layers.

This is done with epoxy, but only on dry wood and with specific method. Absent that, I’m sorry, but you’ll need to try to remove all the teak piece by piece. If you are careful; it will work. If some ply come along; it won’t matter.

 

Thanks for that. Regarding the ingress, the teak you see is a cockpit bench that is exposed to the elements. I cannot think of anything inside the galley cabinet that would cause the delamination from underneath. I plan to investigate the source further with a moisture center on the next trip to the boat.

 

It is possible that there is a small defect int the caulking.
But
Since it is over the galley. I think it is more likely to be steam/ heat related. I don't see any sign of moisture on the exposed inner ply. I do see what could be alligator on the vertical panel that could also be caused by heat. Or i could be seeing photo flash.

Your repair options depend on…
+ the plywood uncompromised thickness
+ the dimensions of the effected panel
+ your cosmetic expectations

 

I agree with Blueknarr about the galley probably causing the problem on the interior.How far away is the galley stove?Replacement of the damaged parts might not be the simplest of jobs,but it ought to be possible and it might be a sound move to add a metal heat shield on the underside-spaced off the surface by a little,to create an air gap.One justification is that lots of epoxies soften to the point of losing strength at 95 deg C.

 

See photo below for the distance between the compartment and the stove. Can't really think of anything stored in the compartment that could have done that kind of damage. All we keep in there is dishes, soap, coffee, and sunscreen.

 

Sorry about the false lead.

I hope that you are wrong about the construction.

I hope that it is a fiberglass panel with surfaced with teak screwed from the underside, and thin plywood covering the screw heads.

Check this by drilling a small hole in the damaged area. I hope you find a void or FG within 1/2 inch.

Also are there any spots on the teak that take longer to dry than the rest of the panel. This is an indication that water is soaking in farther.

 

You know, now that you’ve given us a better picture, I have to say; the design is pretty poor. There really is nowhere for water to go, and varying rates of expansion are certain.

What woodworkers know is wood typically expands at varying rates longitudinally and more, but consistently radially. This means the teak boards that meet the fixed wall on the ends are certain to work against their seals, and the radial edge against the fixed back is also a likely source of leak, but the worst offender is the place where the teak itself is running radially against longitudinals.

For these reasons, and the fact no guttering was added, I recommend you remove the teak.

I don’t agree the spaghetti pot caused it. It is a bad design and there needed to be a gutter around the inside edges.

 

That looks like a well built boat,the curved corners of the galley fiddles and the reliefs at the ends of the treads of the steps indicate a careful builder.Do you have any idea of the thickness of the plywood beneath the teak?it may simply be flex.Alternatively,the teak may be moving as fallguy suggests,and without a beadbreaker tape at the base of the rebate the sealant may have pulled away from one side of the groove.Which would be enough to let water enter.I was a little surprised to see no margin piece at the end of the deck planks that abut the aft bulkhead of the cabin,as I have normally used them all round the deck planks.It may also be that the correct primer wasn't used with the mastic in question.I haven't laid a teak deck for quite a while but you do need to take note of the instructions that apply to the mastic and if they dictate using a primer on porous surfaces,then you need to do just that.The planks shouldn't be a tight fit in the space available and one of our local builders is in the habit of using a radius ball to avoid hard corners where the mastic meets an upright surface,which may be a technique you can adopt.

Can you get inside the locker and inspect the underside?A similarly fine resolution picture of the underside might be able to provide a few more clues.

 

Ideally you would remove the deck area and rebuild it. However, if there are no apparent leaks (the damage may be from moisture in the locker), a quick repair is to scrape the loose veneers and glue a piece of plywood over it to stiffen the deck. It will get you sailing this season and the job can be left for next winter.

 

The teak is not original; was replaced roughly 20 years after launching and not by the original builder. I'll take some more detailed pictures next time I'm there. Not sure how thick the plywood is beneath the teak. Hopefully a more detailed examination will reveal where the source. Consensus seems to be remove the teak and start fresh. Time permitting, that's likely where this is going.