Advice needed for top coat on interior window trim and sill

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Forum topic by JayEs posted 01-04-2017 02:51 PM 1375 views 0 times favorited 6 replies Add to Favorites Watch
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2 posts in 654 days

01-04-2017 02:51 PM

Topic tags/keywords: question

Hello everyone. I’m seeking advice for the “best” finishing/top coat for my interior window trim and sills. I’ve spent the last few weeks removing six coats of paint and some very old stain from the wood. I don’t know what kind of wood it is, and honestly I don’t know how I could figure this out without an expert coming over and looking at it. I’m pretty sure it’s a hardwood, in a Victorian building built in 1904.

I’ve picked out an oil-based stain made by Zar, and am reading to start staining.

But I’m not sure what finishing coat I should use. I’ve read about all of the various possibilities, and it seems like good old-fashioned shellac might be the best choice…all things considered. However, the window sills do get quite a bit of sun and some moisture if left open during rain. A downside of shellac (I think) is that it doesn’t provide any protection against sun damage.

I’m wondering if it’s a good idea to use a spar varnish instead; and, if so, what is generally considered a reliable brand.

Any help is really appreciated. Thank you in advance.

6 replies so far

View JBrow's profile


1366 posts in 1066 days

#1 posted 01-06-2017 03:03 PM


I used polyurethane on window trim adorning three south facing windows. I used pine that was stained. After 12 years, the finish remains in good shape. While I do not specially recall, I think the windows I installed offered low e glass which reduces UV penetration.

I have used spar urethane on some projects, including a pair of outdoor tables that set under an awning. The sheen on the top surface of the outdoor tables seemed to dull after a couple of years. Last year I did a light sanding to remove any grim and re-coated (there was no flaking or cracking). Even though the outdoors are protected from direct sunlight, the tables get dirty and wet from blowing rain, which may be the reason for the dulling. The spar urethane has held up well on indoor projects. I suspect however, that the spar urethane is not the tough finish offered by polyurethane.

View 9x9's profile


82 posts in 1386 days

#2 posted 01-07-2017 02:59 AM

General Finishes EXTERIOR 450

I use this on my front door that gets a lot of afternoon sun

-- Youngsville, LA

View Bobsboxes's profile


1369 posts in 2810 days

#3 posted 01-07-2017 03:17 AM

I used poly on my hickory sills and trim , it’s been 6 years and they still look like the day we put them up.

-- Bob in Montana. Kindness is the Language the blind can see and deaf can hear. - Mark Twain

View pintodeluxe's profile


5757 posts in 2959 days

#4 posted 01-07-2017 04:32 AM

Pre-Catalyzed lacquer is my favorite finish, and has held up great on trim and sills. My concern with your project is the wood is contaminated with the old finishes, various oils, and who knows what else. The safe bet would be to use a sealer coat of Shellac, then a standard topcoat or two. If you plan to spray it on, I would use lacquer without question. Since it is existing trim I assume it will be wiped on, so lacquer may not be the best choice for you. General Finishes Arm-R-Seal wipe on urethane may be a better option for this project.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View JayEs's profile


2 posts in 654 days

#5 posted 01-09-2017 08:24 PM

Thanks everyone for the information!

View 9x9's profile


82 posts in 1386 days

#6 posted 01-20-2017 03:48 PM

give us an update —— What did you use & How do you like it?

-- Youngsville, LA

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