What is the very best way to paint a smooth-star fiberglass exterior door by Therma-Tru? Use alkyd or latex paint?

Angie asked 4 years ago

I just bought a brand new smooth-star exterior door from Therma-Tru. The door is for my back-north facing-patio. We live in northern Utah where the weather can literally range 30-40 degrees in one day. The door-for the most part-does not get a lot of direct sun, but it does get hit by wind, rain and snow sometimes.

I do not care how long the process takes I want the door to look really good. I have no problem using oil based paint but I am familiar with latex paints and have used them throughout my home. I will be either brushing or rolling the paint myself. I will not attempt to use a sprayer at this time. The color I have chosen is a soft, muted sage green by Benjamin Moore. I actually purchased a quart of Benjamin Moore Exterior MoorGlo Soft Gloss in the color, but have since questioned if I’d like to go this route.

After buying the paint I realized it was not too smart of me to test the paint colors on the actual door. I went back to ACE Hardware and told them I needed primer to cover the paint…they sold me an alkyd primer (I brought the actual paint with me) and unknowingly I put the primer on the spots where the paint was. It didn’t adhere so I ended up, after waiting at least 10 hrs or so, sanding the entire exterior side of the door. Unfortunately I had also painted the molding around the glass (the door is mostly glass).

So now I’m in a couple predicaments. I’ve sanded off most if not all the factory pre-primer (I think) so the door needs to be primed. I will either have to sand the molding or repaint it with a primer that can cover oil based primer, if I am going to use exterior latex. I am not worried about cost because my ACE is excellent about returns even used items especially since they sold me the wrong product. But I also have a Benjamin Moore specialty store very close to my house as well as a Sherwin Williams Specialty store is close too.

What do you suggest I do? Did I ruin anything sanding the entire door? It doesn’t seem like anything is wrong except it is shinier and smoother now (it had a primed-kind of texture before). I also wiped it down with TSP since sanding it in an attempt to take away some of the ‘glossiness’. So Basically…I guess I’m starting with a bare door with the exception of the oil based primed molding.

3 Answers
anon e mouse answered.

I’d just like to confirm that the Therma Tru guy got it backwards.  NEVER put latex over oil.  It will blister and you will have a  mess.  Frankly, to be safe, I always put an oil based primer on old paint that I am not certain what it is.  The alkyd (oil) based primer will seal any kind of paint and bond well with latex and you will be fine.  If you are using darker paints, you can even have the primer tinted so the latex covers better.  
Hope that helps 

Renee answered.

The Therma Tru guy is correct. Latex can go over oil but not oil over latex. Latex is less stable and if it fails the oil finish will come up with the latex. To paint over oil; clean, lightly sand down the shiny finish or use a bonding primer. Apply the latex. If the latex blisters it’s because moisture got under the latex finish or the oil finish wasn’t prepped properly before the latex was applied..

MagicDave answered.

For Painting Doors please see my web site page : //davmagic.com/paint/PAGES18.html and really …it IS possible to paint latex over oil AND oil over latex (BOTH) with good results… but it really depends on several factors… the Quality of your Product, the ability of you to apply the materials Correctly, the choice of Tools for application, and finally, the weather conditions at the time of application and for approximately 2 weeks afterwards… You just need to TEST the situation when in doubt! Good Luck! BTW it always is better to use an Oil Base Exterior Primer for Exterior Doors and other Exterior work!

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