View Full Version : Refinish of Therma-tru Fiberglass Entry Doors

07-15-2011, 08:42 PM

I thought I posted this earlier but I must've screwed-up somewhere...

My usual finisher begged off re-finishing a fiberglass front door and sidelights that I installed for a client around five years ago. I sent him the manufacturers link that listed recommended strippers: www.thermatru.com/pdfs/StainInstructions.pdf Point of interest is item #1 pg. 5, where they basically say to ignore the stripper mfg's warning about their use on fiberglass.

When I spoke to him about it, he said that he had asked around (I think there are paint and finish pro forums he visits), and that some guys have reported troubles re-finishing fiberglass doors. I don't know if they were referring to Therma-Tru doors specifically. He preferred not to risk it.

I reluctantly stained and finished the doors originally using the TT proprietary finish kit. They're very nice doors with triple-pane leaded glass,and structurally they have held up very well in a direct sun location that had always been a problem for wood doors. The finish is guaranteed five years and that's exactly how long it lasted.

I'm thinking about tackling it myself especially armed with the finishers bid that the HOs have accepted (he priced it not realizing they were fiberglass). I'm even more reluctant than I was the first time I finished them because as much as I've made peace with painting and finishing and am actually pretty good at it, I loathe the mess and all of stripping. I'm more reluctant to leave a generous payday on the table. Also, I'm slated to start a nice master bath remodel for this client before summer's over; they're anxious to get this door done and new Baldwin handleset installed.

Anyone have any experience stripping fiberglass doors?



07-15-2011, 08:58 PM
Anyone have any experience stripping fiberglass doors?




I've been installing those doors for years, and I wondered how it would go, once the finish wore off. Please post your results when you do the job, as I'm really interested in what / how it goes.


Why not buy one of the strippers in the link you provided:

Bix Quick Stripper™ • Bix Tuff Job™
• Savogran SuperStrip™ • Kutzit™
• Dad’s Easy Stripper™ • 3M™ Safest Stripper™

And do a test spot in the bottom section of one of the sidelights. Just a dab, about the size of a quarter or so, just to see what happens.

I'm sure that the folks @ Thermatru would be more than happy to help you out. They've always been more than accommodating to me.

Good luck and keep us posted.

07-16-2011, 01:24 AM
Hi Chuck---

I did speak with Therma-Tru and you're right, they were helpful and reaffirmed what their PDF stated. It's just that my finish guy, who is real good, got squirrelly about it.

If no one stops me with a tale of woe, I will probably give it a shot. I still have a finish sample on fiberglass from the original finish kit that I can do a test on... good idea!

Only the exterior needs refinishing. It'll be interesting to keep the stripper confined to just the exterior plane of the door, and to remember to keep stripper-covered fingers off of the interior while I work. It'll probably be a good idea to mask and paper the interior in case I have a stripper-induced brain meltdown and grab the door edge. I think I'll take it off the hinges to strip it so I'm not working over wood floor with it open, but the sidelights will need to be done in place.

I'm bad about taking pictures, but I'll try to remember this time and if I do it I will report back.



07-16-2011, 07:02 AM
Use masking tape around the perimeter of the door and plastic or waxed butcher paper on the inside of the door. Be certain you press the tape on firmly, use a putty knife to do so. Do not use masking paper on the inside, the stripper will be absorbed and ruin the finish, if you touch it with your stripper covered fingers. I have never striped a fiberglass door but I have done many other 2 sided surfaces, where I had to save 1 side and the edges.

Good luck with your project.


07-16-2011, 10:29 AM

One thing I'm concerned about IS the masking. On the exterior of the door the homeowner had taped a decoration or notice on the door and it looks like it pulled off the finish. I'm hoping that this was only because the finish was already shot; I'll inspect closer to be sure. Will blue tape seal well enough and resist the stripper?

Also, I've been under the impression that stripper eats plastic and that's why it's usually in metal cans.I was thinking that paper was safer than plastic for this reason. You point about soak-through is well taken. I do have butcher paper, but it's plastic coated. I think I've used gloves of vinyl or nitrile while stripping and they haven't dissolved on me.
I would think latex is out.

Thanks for the reply. Looks like I'll be doing a test run on the stripper, the fiberglass sample and all the components of the job I might be using.


07-16-2011, 01:58 PM
Use one of the citrus strippers that come in the plastic jugs. Never had any stripper dissolve one of my plastic scrapers.

Just make sure the tape is pressed well onto the surface. With the edges being protected from the sun, I think the have a good chance of surviving. You can also finesse the stripper to the tape, a little sanding along an edge/corner is easily disguised.


07-25-2011, 07:53 PM
They're stripped.

Took some progress shots on my phone but they look like the lens was covered in pocket lint.

I'll post some real pics when I go back to stain.

Therma-Tru doors can indeed be stripped, but in the sense that one could tow a rowboat full of reporters to Alcatraz with a rope clamped between one's teeth. http://www.jacklalanne.com/jacks-adventures/feats-and-honors.php

No amount of planning and testing prepared me for that job. My finisher was no fool, but I think I know a big one.

I'm sure the end result will be very nice; the stain, which proved impossible to get out of the nooks and crannies of the raised panels and which the stripper and the factory butyl caulk turned nicely black, will give the doors the kind of antique-look that is considered so stylish today.

The fiberglass is much more unevenly porous than the oak jamb and trim.

TT's recommendation was to leave stripper on for no more than 2-3 minutes which works to quickly remove much of the clear coat but not all, necessitating another application to strip the stain. I used #000 steel wool to try and remove the finish and stain from the sculpted moulding surfaces but suspecting the steel wool of turning the stain black, I switched to 3M #000 synthetic (Scotch-brite) No significant difference in color or pad-clogging between the two.

TT's stripping advice about the 2-3 minutes is apparently based on the fact that their fiberglass has a primer that we are supposed to leave intact. I found this to be impossible, because 1.) changing pads brushes, etc. could easily total one third of that time, and 2.) Once you're through the primer (which may be mythic) and you're into the un-primed fiberglass to any degree you have to go with it on the whole door to get anything like evenness.

Add-in the gobs and streaks of black caulk that the stripper has turned into Henry's Asphalt Emulsion http://www.henry.com/roofing/asphaltroofcoatings/emulsionsandprimers/107asphaltemulsion and the whole thing turns wonderfully artistic.



4 pairs heavy duty stripping gloves.
2 med. brass bristle brushes
2 fine brass bristle brushes
1 pack #000 steel wool
2 packs #000 scotch-brite
3 lbs. white rags
3 quarts Kleen-strip ks-3 premium ( TT approved)

07-30-2011, 09:17 PM
Long story, short---Re-clear coat every two years.

Avoid strip and re-finish.


08-14-2014, 05:59 AM
Well I second that! Those doors are fantastic, we have been installing them from quite a while. I prefer them for the environmental friendly behavior they have. They are durable, maintenance-free and affordable. And as far as appearance is concerned, I think they look fantastically flawless: they are lookalike of wooden doors. Built tougher than regular doors, performing better under sudden climate changes and being able to be customized for your specific needs. I think it is a perfect solution and stand against the misuse of wood. Well, Therma-Tru is credible and I am sure your experience will be delightful.