Thread: Red Cedar Deck Repairs

Chemical strippers can work, but often can get into and on places we'd have preferred to not have it be. Most strippers will attack the 'glass repair areas, but some arr formulated to be kind to these things, if the instructions are followed (don't leave it on too long). Chemical strippers can also stain the wood, which will ruin a bright finish (clear finish) or at least make it a much more difficult job.

Scraping is the best way with sanding a second choice. This way you can control how much you're removing and you can see what you're doing. Bring healthy elbows.


If it's really varnish (not polyurethane) all you have to do is feather out the really bad areas and "flow" on some more varnish. Build up enough finish to permit leveling the surface without sanding or scraping into the raw wood and you're go to go.

If it's polyurethane, which you can tell by the smell of the sanding dust, and the coating is cracked or lifting, then it all has to come off. You just can't repair most of the poly's like you can varnish.

You'll need several base coats (bulking coats) and several finish coats. The coats last put down will receive most of the damage from abrasion and UV. If this coating is thick enough, you can repair it. If it's not thick enough, the base coats and eventually the wood itself gets damaged.

As a rule, more thin coats is better. In tropical environments, you'll need once a year varnish touch ups, if not full recoating. The polyurethanes can last a little longer, but are harder to repair. The linear polyurethanes (LPU's) are even more durable, but also are the hardest to apply and repair.

Once you get the areas sanded down and ready for finish, you'll have a better idea of how badly damaged the surfaces are and what route you want to take.

Varnish and other clear coatings is one of the things where you get what you pay for. Hardware store varnish will fail quickly. The stuff I use is almost $300 a gallon, but I get long term durability, very high gloss retention and a level of finish that's hard to match with other products. Maybe you don't need this high end stuff, but a good middle of the road material is a better investment then uncle Bob's special mix at the local hardware store.

Great, thanks for that. these forums are a gold mine of avoided mistakes for beginners!

Just one query on the varnish/ polyurethane question. You mentioned a difference in smell - is there any further description of that difference? Is one more distinctive than the other?

Any other ways to tell the difference? I suspect varnish as the previous owner mentioned he re-did the varnish once a year whilst he had it... I suspect that job would have been a little difficult if it was polyurethane and it all had to come off each year.

So if it is varnish i could-
- scrape away all of the flaking bits the.
- retouch thin and bare areas to level it out.
- light sand over the whole boat.
- and a couple of coats over that again for further protection.

heres a view of the cockpit


Cheers, Adam

No, it takes a fairly experienced nose to tell what the finish actually is. One give away is that varnish usually has much more "color" to it then polyurethanes. A flake of finish that appears quite amber, is varnish, but if it's reasonably clear with just a hint of a tint, they it's likely polyurethane.

Once varnish has broken down to the flaking stage, it's lost most of it's usefulness. It's probable there is some wood damage and this can only be repaired as raw wood.

If you do find areas that seem well stuck, then you might be in luck and flowing on some more will bring back the finish.

A few coats just can't get the job done. My minimums are at least 4 base coats and 3 finish coats. This is a pretty thin finish, which will have to be promptly repaired if chipped, scratched or other wise damaged. On a show boat, I'll have over 20 coats of varnish.

There are two stages to applying clear coatings. The first is the build stage, where you bulk up material to provide a protective base, covering the wood. The second is the actual sacrificial finish coats, which will be literally burned off from UV and abrasion. In a perfect world, you only have to recoat the finish every so often to restore the very last few coats that have been eaten by UV or physically rubbed off.

In reality, like your boat, there will be areas where the finish coats can be "saved" and other areas where the whole shooting match has to be stripped off, the wood cleaned up and refinished.

With a project like yours, my first response would be to start with a level playing field and strip everything down. This way, you know what you've got and when it was applied.

Good varnish work is difficult to do. Lots of run and sag free coats have to be applied, with the last few needing to be as dust and bug free as possible. Other then a climate controlled shop, this is often very difficult to get under the shade tree in the backyard.

Polyurethanes can help in this regard. They dry a whole bunch faster (tack free in less then an hour, and my fancy LPU stuff is dry to the touch in 5 minutes), which can help keep bugs from committing suicide in the wet finish. Poly's can also "lay" down better, leaving few if any brush strokes. On the other hand, don't get the additives right, work in the wrong humidity, don't have it thinned properly, etc. and you'll cry for hours.

I was against the new clear finishes for a long time, but they've now developed products that are very good. Maybe I've just gotten used to using them and now can do it with a level of confidence, that makes it easier for me to accept them.

Practice on an oar or thwart first, before you go after that deck.