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Thread: So, how about those fiberglass Thermatru doors and top coats

  1. #1

    So, how about those fiberglass Thermatru doors and top coats

    I know there are a lot of threads about finishing front doors and quite a few of them deal with Thermatru Fiberglass doors. All of the ones that I have found on the forum are from several years ago and do not seem to address my specific line of questioning. I read a few that mention the kit Thermatru sells is a good option but it cost over $200. In my attempt to save money I purchased an unfinished door and have already applied a Min-wax Gel Stain Oil-Based product. My door faces west so it gets full sun for 50% of the day. I plan to build a porch on the front of my house to mitigate sun exposure but mainly for re-sale value. Although the porch project is most likely a year or two out. I have been looking at the General Finishes Exterior 405 and was about to purchase it when I searched for the best way to apply the finish and ended up here.

    After reading everything for a day or two I have few questions:

    - Does anyone know if the GF 405 will hold up for at least 2 years before I build the porch? I would prefer 3 years in sun just to make sure it looks good after the porch is built.

    - I was planning to cut whatever top coat I eventually go with and brush it on. Although I am not above buying a cheaper Harbor Freight airless sprayer and spraying. The only catch is that I would be spraying in my garage. Is a cheaper airless sprayer good enough to get a decent finish and is it advisable to spray in my garage if I take the necessary precautions?

    - We would like to use a matte finish for the top coat. I have only ever used satin or semi gloss and was also curious if it holds up to weather any differently?

    Glad to be a part of the group.
    "A bad day woodworking is better than a good day working"

  2. #2
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    Among other things, I make doors that get shipped to Alabama. We source fiberglass slabs from a number of manufacturers and I know the folks at ThermaTru well. They make a great door. slab. A door facing West with no porch or overhang is a leak waiting to happen, especially if you have a low or ADA threshold. A lack of overhang voids the ThermaTru warranty. If you have a storm door it helps stop leaks, but the Western exposure turns it into a solar oven. No finish that faces West will last long, especially if it's dark. From ThermaTru's website:

    All exterior finishes are affected by exposure to sun, weathering,
    moisture and air pollutants. Typical durability of the topcoat is 35
    years, but may be less, depending upon site-specific conditions.
    When the gloss has decreased or the topcoat feels rough, its time
    to reapply a new layer of topcoat.

    I'd reach out directly to the GF folks for guidance.
    Sharp solves all manner of problems.

  3. #3
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    I doubt GF is going to promise anything about longevity since you aren't using one of their stains. And as Rob said, West facing doors are a recipe for failure, dark colored ones especially so.

    I have Exterior 450 satin on one door that faces directly South, behind a storm door, that gets direct sun several hours a day. I vented the door to keep the temperature down and had 3M film installed on the glass to cut the UV and heat gain. It's been in for 2 years now and the finish is fine.

    Exterior 450 goes on easily with a brush. There's no need to thin it; just add a little Extender if you need more open time.

    Will it last 2 years? If it gets direct rain exposure as well as sun, and you get enough Winter down there for real freeze/thaw cycles, my guess is no. No real Winter would up it to a definite maybe.


    John

  4. #4
    Quote Originally Posted by Michael A Harris View Post
    I know there are a lot of threads about finishing front doors and quite a few of them deal with Thermatru Fiberglass doors. All of the ones that I have found on the forum are from several years ago and do not seem to address my specific line of questioning. I read a few that mention the kit Thermatru sells is a good option but it cost over $200. In my attempt to save money I purchased an unfinished door and have already applied a Min-wax Gel Stain Oil-Based product. My door faces west so it gets full sun for 50% of the day. I plan to build a porch on the front of my house to mitigate sun exposure but mainly for re-sale value. Although the porch project is most likely a year or two out. I have been looking at the General Finishes Exterior 405 and was about to purchase it when I searched for the best way to apply the finish and ended up here.

    After reading everything for a day or two I have few questions:

    - Does anyone know if the GF 405 will hold up for at least 2 years before I build the porch? I would prefer 3 years in sun just to make sure it looks good after the porch is built.

    - I was planning to cut whatever top coat I eventually go with and brush it on. Although I am not above buying a cheaper Harbor Freight airless sprayer and spraying. The only catch is that I would be spraying in my garage. Is a cheaper airless sprayer good enough to get a decent finish and is it advisable to spray in my garage if I take the necessary precautions?

    - We would like to use a matte finish for the top coat. I have only ever used satin or semi gloss and was also curious if it holds up to weather any differently?

    Glad to be a part of the group.
    As long as you allow the gel stain to dry I don't see a problem. If it's cold where you are it may take a week for the stain to dry. It should work alright to brush the finish on. A fiberglass door is what a gel stain was invented for. When brushing any finish try to apply the finish with as few strokes as possible. The more you brush it the more the brush strokes will show. Over brushing gets air in the finish and causes it to set up before the finish has a chance to flow out.

  5. #5
    Quote Originally Posted by John TenEyck View Post
    I doubt GF is going to promise anything about longevity since you aren't using one of their stains. And as Rob said, West facing doors are a recipe for failure, dark colored ones especially so.

    I have Exterior 450 satin on one door that faces directly South, behind a storm door, that gets direct sun several hours a day. I vented the door to keep the temperature down and had 3M film installed on the glass to cut the UV and heat gain. It's been in for 2 years now and the finish is fine.

    Exterior 450 goes on easily with a brush. There's no need to thin it; just add a little Extender if you need more open time.

    Will it last 2 years? If it gets direct rain exposure as well as sun, and you get enough Winter down there for real freeze/thaw cycles, my guess is no. No real Winter would up it to a definite maybe.


    John
    Thank you for the advice. I am interested in this venting you talked about. Can you steer me in the right direction?
    "A bad day woodworking is better than a good day working"

  6. #6
    Thank you all for the advice.

    I should have mentioned the door is set back from the front of the house by about 3-Ft creating kind of a vestibule with soffit overhead. Unless rain is coming at a decent angle it shouldn't get very wet. The door has been in my garage for 4 days after today with a space heater running in order to make sure that gel stain dries completely.
    "A bad day woodworking is better than a good day working"

  7. #7
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    Quote Originally Posted by Michael A Harris View Post
    Thank you all for the advice.

    I should have mentioned the door is set back from the front of the house by about 3-Ft creating kind of a vestibule with soffit overhead. Unless rain is coming at a decent angle it shouldn't get very wet. The door has been in my garage for 4 days after today with a space heater running in order to make sure that gel stain dries completely.
    That's good news. A vestibule offers good weather protection. Regarding venting for the storm door......

    Many doors marketed now are "all glass" as opposed to a version with a sliding self storing storm window. If you want the all glass variety, make sure the glass panel is either vented top and bottom to allow the hot air to escape or has a removable glass panel that can be removed and stowed in the summer months with a screen remaining.
    Sharp solves all manner of problems.

  8. #8
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    It's not just the Summer months you have to worry about with a storm door over a wood door. I learned about the need to vent a glass storm door the hard way; after panels in the nice new door I put behind it split - in December! I had argued against the storm door from the get-go with the homeowner but he insisted it remain. So when the problem happened I wasn't all that surprised, nor was I surprised by when it happened. It is a South facing door so the sun exposure is more direct and over a greater portion of the door in the Winter than Summer.

    OK, what to do about it. Obviously, I fixed the door. That was not an easy task, but I removed all the solid panels and replaced them with back to back panels so there would be less stress on them from the different conditions outside vs. inside the house. The storm door is a narrow aluminum frame around a large glass panel. There are a couple of companies that make storm doors with a built in venting option, but this wasn't one of them. So to vent the door, I removed the bottom seal and drilled 1/2" holes up into the lower rail to meet 4 or 5 holes I had drilled on the inside of the rail to hold 1" louvered vent plugs. I did the same in the top rail. So air comes up through the bottom rail, between the storm and house door, and vents out the top rail. I also had the home owner have a company come out and install one of 3M's heat and UV blocking films to the inside of the glass. With those three changes the door has been fine ever since; about 18 months.

    John

  9. #9
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    Quote Originally Posted by John TenEyck View Post
    It's not just the Summer months you have to worry about with a storm door over a wood door.
    Agreed, but the door slab the OP is dealing with is fiberglass sheet molding compound (SMC) with an interior of injected polyurethane foam. It's a little more forgiving from a thermal perspective.
    Sharp solves all manner of problems.

  10. #10
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    Quote Originally Posted by Rob Luter View Post
    Agreed, but the door slab the OP is dealing with is fiberglass sheet molding compound (SMC) with an interior of injected polyurethane foam. It's a little more forgiving from a thermal perspective.
    So are you advocating that the OP add a storm door? One would think that a composite door like Thermatru would be more forgiving than a wood door when covered by a storm door, but I've seen all manner of plastic mouldings used on house doors deformed and nearly melted when trapped behind a storm door with direct sun exposure. I have no idea how the SMC of a Thermatru door compares to those plastics, but if the OP is thinking about adding a storm door to protect the finish on the Thermatru door, I would recommend a vented one. Adding the 3M film would help significantly, too. The UV reduction is over 95% and the heat gain on the one we used was 50%.

    John

  11. #11
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    Quote Originally Posted by John TenEyck View Post
    So are you advocating that the OP add a storm door? One would think that a composite door like Thermatru would be more forgiving than a wood door when covered by a storm door, but I've seen all manner of plastic mouldings used on house doors deformed and nearly melted when trapped behind a storm door with direct sun exposure. I have no idea how the SMC of a Thermatru door compares to those plastics, but if the OP is thinking about adding a storm door to protect the finish on the Thermatru door, I would recommend a vented one. Adding the 3M film would help significantly, too. The UV reduction is over 95% and the heat gain on the one we used was 50%.

    John
    My point was that material degradation (cracking) and thermal stresses are less of a concern. SMC is a thermoset material that doesn't soften or deform at higher temps.
    Sharp solves all manner of problems.

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