Please help with new finish for shed/office

chancee

New User
chancee
Hello everyone, I was hoping to get some advice as to how to proceed with my project. Eight months ago I put the cladding on my new shed/office I built on my property. I have sort of a unique situation in that for the cladding I used wood that I created with a hybrid shou sugi ban method. By that I mean I started with Pine cladding from Home Depot. I slightly burned the wood with a weed torch enough to bring out the grain. I then painted on Varathane Weathered Grey Stain and quickly brushed it off. After that I sealed it with Minwax water based Spar Urethane - 3 coats.

And that's now where my problem comes in. It's only been eight months and the wood isn't looking so great. There is mildew forming as you can see from photos on many of the boards. This is very disappointing because I put over a hundred hours into preparing this wood, installing it, etc. I have been able to get about 75% of the dirt/mildew off with soap/water/laundry detergent/clorox.... but unfortunately on some of the boards it's not going anywhere. I just bought some JoMax at Home Depot and I'm going to try that next.

My bigger issue is - how do I protect this wood moving forward? At first I was just going to reapply the water-based Minwax, but I see now it's pointless. I live in Atlanta and the shed is also fifty feet from the Chattahoochee river so things can stay humid. We have a had a brutal past eight months with remnants of hurricanes coming through plus an unseasonably wet summer.... so I'm sure that's contributed to the mildew forming.

One of my biggest problems is I can't really sand the wood because it will take off the unique designs in the wood from the above mentioned process I used. When I sand the wood it just scuffs up the urethane layer. I have been able to get the wood looking somewhat nice again even though there is some mildew left so if there was just some kind of impenetrable sealant layer I could now brush on over, I'd be in good shape.

Finally, I've looked over the forums and seen people suggest things like Waterlox, Sikkens, etc..... so I was just hoping to get some expert advice on which way people think I should go with this. My goal is to find something that actually works, is clear, and is something that I have to reapply as infrequently as possible because it's a big job! Thanks in advance! -Mark
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SteveHall

Steve
Corporate Member
I'm assuming the mildew is forming on top of the finish and not under it? How easy is it to clean off, can you easily wipe it off or is it actually eating the finish itself?

Most modern exterior finishes have mildewcides in to them to prevent this. Probably your spar urethane didn't. (Some finishes, especially old oil-based ones, actually have organic ingredients that encourage mildew growth... even worse.) No matter the product, simple accumulations of dust and organic materials (pollen, snail trails, etc.) over time will eventually build up enough to encourage growth. You'll probably have to commit to a good power washing with a mildewcide once a year unless you want to apply another product over top, although I'm not sure what could be applied over a spar urethane.

The point of shou sugi ban is to burn out all the organic material on the wood's surface so mildew, fungi, and insects have nothing to eat. A side benefit is also having nothing organic to burn as well. But then the material will have a black, charred, pure carbon finish. Some recommend an oil then be applied, but unless this is non-organic, it nullifies the whole point of the process.
 

Jeff

Jeff
Corporate Member
+1 to Sikkens Cetol. There's a clear and other 5 colors available.

 

chancee

New User
chancee
Thanks for responding everyone. Yes, that's tongue and groove. I had looked at the Cetol Log and siding but it looked like you had to get it with some kind of tint mixed in. If they have a clear one that would be great....
 

Phil S

Board of Directors, President
Phil Soper
Staff member
Corporate Member
Thanks for responding everyone. Yes, that's tongue and groove. I had looked at the Cetol Log and siding but it looked like you had to get it with some kind of tint mixed in. If they have a clear one that would be great....
I am sure they have clear
 

Dee2

Gene
Corporate Member
In my previous life in the CSRA, we built a Lindal Cedar home and the outside was cedar siding. We were on a heavily wooded lot. I would take a week off every spring, rent a man lift (the back side was 3 stories (drive in basement garage), wash the entire exterior with oxygen bleach (doesn't kill the plant life) and retain. Every year I used more of an opaque stain until finally, SW was mixing my own color and tracking it for me. Every year, a weeks vacation, me, the lift, the garden sprayer, and the water hose. It was very therapeutic.
 

Jeff

Jeff
Corporate Member
Thanks for responding everyone. Yes, that's tongue and groove. I had looked at the Cetol Log and siding but it looked like you had to get it with some kind of tint mixed in. If they have a clear one that would be great....
They have a "natural" and a "natural light" but they aren't water white clear because of the oils used.


 

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