Top coating polyurethane with marine varnish on exterior doors.

I have been a professional on site woodwork refinisher for 33 years. It drives me nuts to see people buying new exterior front doors and three years later the finish is turning white and peeling. There is a simple and cost effective method home owners can do.

Sand your door lightly with #220 sand paper. Tack it down with a rag soaked with paint thinner and a little varnish to make a tack cloth. Buy two quarts of Marine varnish one gloss and the other the sheen of your choice.

Take a bristle or preferable an ox hair brush, and brush the varnish on brushing in one direction going from dry to wet. You have to lift and back brush only, because marine varnish will dry so fast you will have a mark every where you set your brush down. Let it dry 24 hours and repeat. You can choose gloss semi gloss or satin.

This method works great,and will last for years. My clients look concerned when they pay me saying “how long will this last”. They are overjoyed when I send them a reminder message after four or five years that it’s time to re-coat. Home owners can do this themselves. It is just real important to use a true marine varnish. I use McCloskey’s Man-Of-War, but there are other company’s that make it. You just have to make sure it is a true marine or spar varnish. Submit questions or success or failure stories or photos.

View Author’s ProfileDale Palmer’s Perfection Restoration

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  1. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    McCloskey Man-O-War marine spar varnish is way better than any polyurethane. Apply 2 coats of spar varnish and not have to worry about your door for a while.

    • Posted May 23, 2015 at 11:23 am | Permalink

      I believe two coats is in sufficient.I always use 4-5.It will look better and last longer.

    • Posted May 25, 2015 at 2:41 pm | Permalink

      I strictly refinish new finish front doors in Cincinnati Ohio. I know that marine varnish is better. I have gone back and recoated front doors 8 years after new finishing or refinishing and sanded and done one top coat and they look like brand new. Valspar makes McClusky’s Man-O-War now. They reformulated it 4-5 years ago. It is not quite as durable as it was before but it still has any other product I have tried beat. I have 39 years in the on site front door finishing refinishing trade.

    • Posted May 26, 2015 at 6:18 pm | Permalink

      Man O War is all I have used for 40 some years!!! It just went up in price again!

    • Posted May 28, 2015 at 11:38 am | Permalink

      I agree that is all i use

    • Posted June 5, 2015 at 12:36 am | Permalink

      I apply 4-5 coats of Man O War.I use gloss for the first 3-4 coats .This keeps it nice and clear I apply the final coat in stain or gloss depending on the taste of the client.

  2. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    I am getting ready to finish an exterior door with stain followed by polyurethane. I purchased an oil-based exterior/interior polyurethane, but will this give the door the same protection as a spar varnish?

  3. Karl
    Posted July 15, 2014 at 7:44 pm | Permalink

    The gloss is the first coat and is used for sealing purposes. I think you could use the same sheen as the final finish for this purpose, example-satin used for both coats. The advantage to using gloss for the first (seal) coat is; a little better penetration than satin and the final coat will slide on a little easier.

    It’s up to you if you want to use 2 different sheens. Personally, I use the same sheen for both coats.

    • Posted May 23, 2015 at 11:27 am | Permalink

      The gloss is also totally clear.If you use 4-5 coats of satin you will have a bit of a cloudy look.They add silica sand to flatten gloss to active satin.That is why I use gloss for the base coats.I am finishing a new cherry door for a client right now.They are very conservative.I used 4 coats of gloss and the final coat they chose satin!

  4. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    I’m a little confused. You say to buy one quart of gloss varnish and one quart of your own preference – gloss, semi-gloss, or satin. But you don’t say how the different “quarts” are used. – Do you mix them together? I don’t understand.

    • Posted May 23, 2015 at 11:43 am | Permalink

      I buy gallons of GLOSS marine varnish to put the first 3-4 coats of varnish on my doors.I do this because the gloss is totally clear.I use satin for the final coat if the client wants satin.They make all varnish in huge quantities in gloss then add cilia sand in increasing proportions to flatten it down to semi gloss satin or flat.The cilia sand makes a cloudy look that I don’t like.If the client want satin I use satin for the final coat.I use cone filters to strain the base coat and ladies nylons to strain the final.Use a bristle brush that has NEVER been used for paint because if there is old paint in the heel you will ghet paint specks in the fresh varnish.ALLWAYS USE MARINE/SPAR VARNISH EXTERIOR!!!

      • Anna Wachtel
        Posted June 25, 2015 at 5:48 pm | Permalink

        I recently bought exterior door Douglas Fur and had it sanded and then stained Mahagony by professional, polyurathaned it. The sanding was unfortunately bad and the 3 coats of polyurethane (not Marine) were applied. The door looks dry, raw completely flat and without life. It’s very upsetting, we would like your advice using on the door marine varnish and sand the door lightly before the application. What are your thoughts? Thank u
        so much, Regards Anna Wachel

  5. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    Use oil base color putty, available in many different colors and it can be intermixed for custom colors. This will remain soft and a little flexible for a while. But, in the end you have to refill the cracks from time to time.

  6. geebee
    Posted July 15, 2014 at 7:44 pm | Permalink

    What would I need to use to fill gaps in tongue and grove caused by expansion and contraction due to heat and cold? We live in Colorado where we can have both extremes in one day. I’d love to refinish my own door, but need to address this issue first. Thanks for the great advice!

    • Posted May 23, 2015 at 11:30 am | Permalink

      Sometimes I have cracks I can’t get to fill.After I finish I sometimes fill cracks with clear cylicone chalk.This will prevent water from collecting in the crack.And it is clear so you will never see it!

  7. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    Can this technique be used over cement/ceramic outdoor sculpture?

    • Posted May 24, 2015 at 7:23 pm | Permalink

      Clear silicone will stick to almost anything except wax. Nothing will stick to wax.

  8. Anonymous
    Posted July 15, 2014 at 7:44 pm | Permalink

    This is excellent advice based on my home owner experience. This article is written for painting professionals. So it is little difficult to follow. A link to YouTube video will solve the problem for DIY guys. Nevertheless the advice is top notch and therefore I gave 5 stars.

  9. pat palencar
    Posted November 7, 2014 at 4:34 pm | Permalink

    Can I use this polyurethane on a flagstone foyer ??
    Someone spilled water on 2 foot corner of the foyer and looks white,
    I need to cover this space.

    • Posted November 13, 2014 at 8:12 pm | Permalink

      Poly and other wood finishes shouldn’t be used on stone. There are clear stone sealers, in different sheens, at your local paint or hardware store that will work better.

      • Posted May 24, 2015 at 7:29 pm | Permalink

        Thank you I am a wood finisher so I am not an expert on stone. I have used Poly on foyer slate and had good results!

    • Posted May 23, 2015 at 11:34 am | Permalink

      If it turned white it got contaminated with water.You can use spar varnish oven OIL BASSED paint.Try a small inconspicuous space.If the varnish separates and won’t flatten out it is water based point and marine varnish won’t stick to it.There are water based ploys but my understanding is they won’t hold up outside!!!

    • Posted May 24, 2015 at 7:27 pm | Permalink

      I have seen people use some type on clear coat on exterior stone. I have not. Varnish is VERY sticky. It sticks to my hands so bad I have to clean my hands periodically during the work day. I would try a small sample and leave it on for a couple of weeks before I would try it!

  10. Pat
    Posted May 15, 2015 at 2:33 pm | Permalink

    Can the Spar varnish be used over a stained wooden door, under a glass storm door with Western exposure? I think the painted surface has bubbled due to heat. I am having the door stripped and starting over.

  11. Al
    Posted August 9, 2017 at 3:30 pm | Permalink

    My only question is can this marine varnish or spar varnish be used after several codes of spa urethane have been applied to the tabletop

    • Posted August 10, 2017 at 12:35 pm | Permalink

      Yes it can. A light sanding with fine paper or sanding sponge is needed.

  12. Tina
    Posted August 28, 2017 at 11:14 pm | Permalink

    Question: I just stripped/sanded/stained (using MinWax wood finish penetrating stain) and put a couple coats of an exterior polyurethane over the “side lights” which are on the right & left of my front door (haven’t done door yet). Can I put the McClusky’s Man-O-War over the polyurethane? Or do I need to restrip and do this over? (NOTE: When I was doing the “light sanding” between polyurethane coats, I noticed that some of the polyurethane was coming up — not just sanding off)…. I live on CO and not sure if current weather (hot but humid day) had something to do with the pealing up during sanding. Wish I had seen this post earlier…

    • Posted August 29, 2017 at 1:27 pm | Permalink

      Yes, McClusky’s Man-O-War can be applied over polyurethane. Humidity slows down the curing, most likely this was the cause of your problem with the poly.

      At this point a light sanding is a good idea to promote adhesion and get a super smooth surface, after removing any dust apply the varnish.

      • Tina
        Posted August 29, 2017 at 3:22 pm | Permalink

        Thank you I very much appreciate the advice!!

  13. Patrice Mayo
    Posted September 7, 2017 at 10:20 pm | Permalink

    Will mariner varnish protect the finish on the door from dog scratches?

    • Posted September 11, 2017 at 2:20 am | Permalink

      Maybe to a point but don’t count on any clear finish to take dogs nails for to long.

  14. LT
    Posted September 13, 2017 at 12:30 am | Permalink

    Is it ok to leave the doors on the hinges or is it best to remove them to apply the varnish? I have heavy 8′ double doors that would be tough to remove. How much varnish would typically be needed for 4 coats to the double doors with transoms and with sidelites? Lastly, should the stain be reapplied before varnish goes on?
    Thanks in advance!

    • Posted September 13, 2017 at 3:47 am | Permalink

      Yes it is, actually it is the only way to apply the varnish to front doors and have them closed at the end of the day. Make sure to remove the weather stripping so the door doesn’t stick.

      You will need a couple quarts. Since the doors will be up your coats will be thin and watch for runs, runs can happen for about an hour after application. Plus make sure all staining is finished before applying any varnish.

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