Redwood fence varnish help

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Forum topic by Evanredwood posted 01-19-2017 10:41 PM 908 views 0 times favorited 4 replies Add to Favorites Watch
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1 post in 695 days

01-19-2017 10:41 PM

I had a redwood fence installed a couple years ago. I’ve had helmsman clear water based varnish applied on a yearly basis.

After some heavy rains this year, the varnish has began peeling and cracking, and the wood has some darkening and has lost its overall luster that it had. After receiving some absurd quotes for sanding and refinishing, I’ve decided to take this job on my own.

I have no wood work experience, so any help is appreciated.

Do I sand, and then reapply? What grit sandpaper should I use? 2, 3 coats? Should I switch to an oil based varnish?

4 replies so far

View papadan's profile


3584 posts in 3571 days

#1 posted 01-20-2017 05:40 AM

I would not sand the fence. I would use a good pressure washer to blast off the old peeling finish and after giving it a few days to dry, spray the fence with a couple coats of Thompsons water seal. Use a pump garden sprayer to apply the Thompsons and respray every spring. Thompsons will seal out the moisture and help prevent sun damage without building up an outer layer that will peel off later.

View OldCoach's profile


48 posts in 1077 days

#2 posted 01-20-2017 06:08 AM

I would refinish with an oil based spar urethane like Helmsman. Water repellent and blocks UV rays. You can thin the first coat up to 50% with mineral spirits or paint thinner to help it penetrate the wood better. Then apply second coat either straight or slightly thinned(10-20%). Depending on how much sheen is remaining will determine whether you need to sand off the sheen from the old coat.

-- Play cowboy on weekends and make sawdust in between when not watching football

View Fred Hargis's profile

Fred Hargis

5177 posts in 2696 days

#3 posted 01-20-2017 12:09 PM

Here’s a different opinion about Helmsman: walk past it to almost anything else for outdoor use. Urethane resins are highly susceptible to damage in a high UV environment; that’s why the true spar marine spar varnishes mostly use other resins. But the UV absorbers in Helmsman are suspect as well. Flexner did some testing of color degradation under spar varnishes; Helmsman did so poorly he speculated that it had almost no UV protection in it at all. Bear in mind, any clear coat film finish will need maintenance over time, the trick is to pick those that require the minimum. So, given your tolerance for taking care of it in mind: the deck stain approach would be the easiest to maintain (probably). I’m not sure what the cost would be, but it’s likely to be an annual job though it should relatively easy. If you want a film finish, true marine spar varnishes are not only expensive, but take a lot of coats to build up the UV resistance. An alternative (test this yourself on a small area if you’re skeptical) would be exterior untinted paint. If you get the base used for darK colors, it will dry clear, have all the UV protection needed, be a lot less expensive, and easy to apply….needing fewer coats than the marine spar. Best would be the oil based variety, if that’s not available in your local, the acrylics (water cleanup) work almost as well. In most brands this is a #4 base, and you can buy some of them in quarts to test out. Here is some more info about it. BTW, using the pressure washer to remove the old finish (and it needs to go) would be the easiest. You may still have to scrape some spots and exercise caution to avoid damaging the wood….but this is going to be work no matter what approach you take.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Lazyman's profile


2636 posts in 1590 days

#4 posted 01-20-2017 12:50 PM

Spar varnish finishes are going to be a constant maintenance issue. Not only do most them only last a couple of years but you have to remove the old finish before applying the new one to prevent the remaining finish from causing the new one to peel off quicker than it should. I think a stain or semi-transparent stain will give you many years of protection. The stain on my shed and fence are both over 15 years old and just now ready for a new coat. The stain will help you get the wood back to the color you want it to be and keep it there longer. Just test it on an inconspicuous spot to see if you get the color you want. Stain can be applied with a pump up garden sprayer but a thicker semi-transparent stain might need a power sprayer like the Wagner airless or their HVLP sprayer.

You do need to get the old varnish completely off before you apply any finish. I second the opinion about using a pressure sprayer to speed that along. You can buy a cheap electric one for around $100 +\-. You may have to hand scrape any stubborn spots with a hand scraper from the paint department. While it’s not necessary, a quick scuff sanding with a coarse sandpaper to roughen the surface after washing and scraping will help with penetration and adherence of the stain.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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