Recently built a grape arbor out of douglas fir 4X6 timbers and am now wondering, what would be best way to finish it? My wife thinks it would be nice to stain white. My concerns are primarily that whatever finish I apply not be toxic and that it hold up well (i.e. I don’t want to have to cut back plant every few years to reapply paint or varnish).
So far I’ve received following advice:
1) Apply nothing. (Posts sit on galvanized u-shaped straps embedded in concrete, major source of deterioration would be ground contact. I live in Pacific NW, lots of rain and moisture.)
2) Apply hardener such as Bentonite or Daly’s ShipnShore Waterproofing Sealer, then finish coat with polyurethane.
3) Apply marine varnish.
4) Apply Owatrol, a non-toxic marine varnish.
5) Apply a type of wax used on breadboards?
Does anyone agree/disagree with these ideas or have other suggestions?
Thanks.
Tom
Replies
Any modern finish is non toxic once it has dried so that shouldn't affect your choice. Any varnish, polyurethane or paint will eventually break down and need to be scraped and sanded before refinishing so they wouldn't be a good choice for an arbor.
Oil finishes and waxes will slow down the weathering somewhat, but they'll weather away on the most exposed areas, if you left the wood unfinished, the end result would probably be the same after four or five years.
Applying a white house stain would work well. Initially, pigmented stains look a lot like paint but, unlike paint, they don't form a continuous film that will eventually blister and peel. Stains, as they weather, "chalk" on the surface and wash away until you're basically down to bare wood after a number of years. A stained arbor would start out white and develop weathered areas as it aged, but it wouldn't need restaining if you liked the look.
Eventually the arbor will fail from rot developing in the joints, but no finish will prevent this from happening, in fact paints and varnishes can accelerate the rot because they can trap moisture under their surface, preventing the wood from drying out on sunny days. Hope this helps,
John W.
Thanks John. What do you think about applying a wood hardener (Benite) or waterproofing treatment (Daly's ShipnShore) prior to staining?
I'm not familiar with either product so I can't comment on them. I'd be inclined to just follow the stain maker's instructions and let it go at that. Most stains are meant to be used without pretreatment, but you could check the instructions or try to contact one or more stain manufacturers to see if they could recommend additional steps. There is a risk that pretreating the wood might cause adhesion problems with the stain.
Being a New Englander, I like the look of weathered wood and I haven't yet seen a product that keeps wood looking new for very long without regular refinishing, which would be impractical in this application.
John W.
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