Can I use spar urethane over water sealer?

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I am making a fence using old wood doors. The doors have chippy paint on them which I want to use that way. I applied Thompson’s water seal and after it dried I realized the paint chips can still flake off. My question is can I apply spar urethane over top of the water seal? I’m looking for a product that will leave a hard layer over the chippy paint so it won’t flake off with exposure to the outside elements. Thank you.


  6 answers
  • Gk Gk on Jun 06, 2020

    It's too bad you applied the Thompson's water sealer. The spar will probably not adhere well because of the sealer and you will probably get peeling and flaking of the spar as a result. If you would have eliminated the Thompson's altogether and just went with the spar that would have been your best choice. Sorry to be the bearer of bad news.

    • Starr Starr on Jun 06, 2020

      hindsight I now realize I should have skipped the water seal. Shoot! I applied spar urethane to a door I made into a headboard and the paint has not chipped off. I think I’ll go ahead and use the urethane and store the doors inside during the winter. I am not connecting the doors to each other but rather attaching fencing stakes on the doors and inserting into the ground. This is not a permanent fence as I am a renter. Thank you for your help!

  • Vimarhonor Vimarhonor on Jun 06, 2020

    Hello. Before combining two different unrelated products I would suggest calling the manufacturers to see if they are compatible. It is well worth getting professional advice before wasting time trouble and product for less than pleasing results.

  • Kelli L. Milligan Kelli L. Milligan on Jun 06, 2020

    Even if you can apply over the water sealer the chipscwill continue to fall off after a while. Just the nature of paint, wood and the elements.

    • Starr Starr on Jun 06, 2020

      I will be bringing the doors inside for the winter I believe as I’m inserting each door into the ground separately using fencing stakes. It’s not a permanent fence as i am a renter. Thank you for you input!

  • William William on Jun 06, 2020

    Thompson Water Seal absorbs into the wood. You can put spar urethane over it. It will not stop the paint from chipping. Wood expands and contracts with temperature and weather. Paint and any sealers do not. That's why they need to be reapplied

  • Deb K Deb K on Jun 06, 2020

    Hello Starr, you should probably give it a sanding or stripping, as sealers or clear finishes will not adhere well to a Thompsons stain and may result in the topcoat failing prematurely. Most likely the clear sealer or polyurethane will end up peeling and flaking off the stain.

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