Best clear sealer for non treated wood used outdoors

[I’ve got wood worm!]

Hey all.
As per the title, I’m looking to get advice on the best clear sealer for a classic panelled Ottoman that was designed by me for use indoors that the client now wants to use outdoors.

The green paint she choose was luckily a paint designed for external use so that helps! The Redwood top was only oiled. The inner construction was a mix between redwood outer frame on a ply panel with a treated C16 inner frame.
She has more of the same green paint, so I’ll give the insides and every surface another few coats but am wondering what would be the best way to weather proof the Redwood lid?

Oh and she wants to leave it on her decking, so I’ll advise to have it on little blocks to raise it 5-10mm to allow for air flow underneath. And we’re in rainy Glasgow.

Thanks in advance.
Dave.
Humble Wood Designs

 

[Jameshow]

Trad oil varnish over oil surely?

Diluted with white spirit first.

How about a BBQ cover too...!

Cheers James

 

[Sgian Dubh]

Hmm? A wide redwood panel and a clear finish probably isn't going to fare particularly well. The best would be a yacht or spar varnish, e.g., Epiphanes or similar from a chandler. All the same, your client would need to instigate a regular maintenance programme, probably annually. And what's bracing that lid to stop it cupping as it responds to weather conditions? And then there's expansion and contraction to consider caused by pooling water on the surface, wide swings in moisture content, and it's quite possible the panel will develop longitudinal splits.

I suspect the most likely cause of short-term failure in general is that it's a piece designed for internal use, so designing and selecting materials, including adhesive, to cope with external conditions were never a consideration. Now your client wants to change the end use. I'd advise her that rapid failure is possible, and that all the risk is hers. Slainte.

 

[Jameshow]

Another thought

How about encapsulating it in epoxy first, then varnish for UV protection.

Cheers James

 

[Jameshow]

How about epoxy ecapsulating it first then varnish to UV protection of the varnish?

Cheers James

 

[AFFF]

Osmo?

 

[Cabinetman]

As Richard said, it’s going to be a disaster area within 18 months. The longest lasting clear finish is a two pack varnish like West epoxy, but even then that won’t last without maintenance. Ian, sorry.
Ps all sharp edges will need removing on the painted areas or that’s where they will start to fail.

 

[I’ve got wood worm!]

Hmm? A wide redwood panel and a clear finish probably isn't going to fare particularly well. The best would be a yacht or spar varnish, e.g., Epiphanes or similar from a chandler. All the same, your client would need to instigate a regular maintenance programme, probably annually. And what's bracing that lid to stop it cupping as it responds to weather conditions? And then there's expansion and contraction to consider caused by pooling water on the surface, wide swings in moisture content, and it's quite possible the panel will develop longitudinal splits.

I suspect the most likely cause of short-term failure in general is that it's a piece designed for internal use, so designing and selecting materials, including adhesive, to cope with external conditions were never a consideration. Now your client wants to change the end use. I'd advise her that rapid failure is possible, and that all the risk is hers. Slainte.

Yes, exactly my train of thought too! Oh clients eh!
I will advise her not to go ahead and simply sell the piece and reorder a more fitting product.

 

[Raclettefordinner]

I’d avoid osmo - we used to use it a lot on doors and windows but have stopped after numerous customer complaints.
Have you looked into polyvine products?
Tristan

 

[thetyreman]

I haven't found redwood pine fairs well outdoors, even with high end yacht varnish, oak would be a much better choice, or if possible if they can cover it up when not in use.

 

[JonOuk]

With anything clear & external I use Osmo UV protection. It’s like most woods outdoors, depending on their position, exposure to sunlight, temperature, and moisture/relative humidity, it’s hard to say how it’s going to hold up.
There’s probably a reason that you don’t see many over here in the Uk!

 

[HOJ]

If you get the commission to make another painted version more appropriate for exterior use, I would suggest you consider using Accoya &/or Tricoya as a material, with a good quality exterior paint system.

One observation I have with the one you have made, is the boards for the lid look like they are bang on with the core of the heart wood, you may well get longitudinal splits opening up down the middle and more risk of them to cup.