Outdoor Finish

[John Samuel]

I am about to start making a red cedar chaise/day bed for SWMBO and could use a hand with the selection of a finish.

The unit will be in a covered courtyard, and will get no direct sunlight. I dropped an old silky oak single bed into the courtyard as an interim measure. After 3-4 years, the NC lacquer started to go white and craze. To be expected, but the point is that it lasted several years. So, the unit is outdoors, but gets no direct sunlight and will get damp only when rain is driven by high wind ... which will happen, but not often.

In short, the unit is exposed to the outdoors, but gets a fair bit of protection.

All my furniture made to date has been finished with NC or acid cure lacquer, plus a couple of pieces finished in a gloss two-pack. Apart from using marine varnish on my little Sabot when I was a kid, and on a few doors, I have precious little experience with outdoor furniture finishes.

Any suggestions gratefully accepted.

[Master Splinter]

3-5 coats of marine epoxy such as botecote (for waterproofing) followed by 2-3 coats of polyurethane varnish to UV proof the epoxy. Scuff sand and reapply the poly when it starts looking shabby (that's before it starts cracking and flaking off, not after!)

[Robson Valley]

Here, we can have temperature swings from -30C in winter to (shade) +30C in the summer afternoons. Thin air and brutal UV. For log homes and serious chainsaw carvings that get left to the elements, Cetol finishes from Sikkens are the products of choice. A yellow-orange cast which I personally don't care for.

[John Samuel]

Thanks guys,

Master Splinter ... is it not standard for marine epoxies and varnishes to be UV stabilised?

[Master Splinter]

Epoxies, well, there are stabilised ones*, but the boatbuilding dudes prefer the standard epoxy + varnish topcoat method, and since marine applications are about the toughest test of water and UV resistance I can think of, I follow their lead.

I have a suspicion it's because:

1) It's not possible to formulate an epoxy that is UV proof by itself; the bonds in epoxy are susceptible to UV by their very nature.
2) Non-yellowing epoxies aren't, for any length of time under Australian conditions,
3) UV absorbers are chemicals which gradually deplete over time as they get broken down by UV, giving them a finite life,
and
4) the poly/varnish topcoat provides a nice indicator of coating failure/maintenance reminder so you have no excuse not to recoat well before the epoxy starts taking UV damage.

*that advertise themselves as non-yellowing in places like England

[John Samuel]

Thanks,

That all makes sense.