Should You Prime Fiberglass Door Before Painting?

Painting your exterior fiberglass doors adds to the appeal of your entryways. The painting process seems easy, but there are critical steps that you need to consider. One step to consider before painting is priming. Priming takes time, and some people doubt if applying primer will give the best results for their fiberglass doors. For this purpose, we have researched expert tips to help you decide whether to prime or not.

It is a must to prime old and worn fiberglass doors before painting. For new fiberglass doors, you also need to prime them. Priming helps you cut down the extra coating for your fiberglass doors. When you prime before painting your door, the paint coating will last longer. Primers seal the original material of the door and fill the porous surfaces for a smooth paint area.

Before priming your fiberglass door, you must know the compatible primer to use. Also, the process of preparing your door for priming will take much of your time. Make sure that you prepare all the necessary tools and materials before painting. If you want to get the best results, keep reading to know how to prime your door before painting.

A wooden French door with small shrubs on the side, Should You Prime Fiberglass Door Before Painting?

Advantages Of Priming a Fiberglass Door Before Painting

Priming is an important step when painting your fiberglass doors. You can still paint an unprimed fiberglass door. But in the long run, the colors will fade fast. There are factory-primed fiberglass doors available, but you still need at least one layer of primer. Even though the process of applying primer takes time, the benefits you get still outweigh your efforts.

Here are the reasons why it is better to prime your fiberglass door before painting:

  • Priming seals the original surface of the door so that the paint won't soak in.
  • It fills and smoothes porous surfaces.
  • It helps bond the paint to the door to make the paint last longer.
  • Priming effectively hides the blemishes like uneven spots or bubbles on the door's surface.
  • It shows the true color of the paint.

How Do You Prepare A Fiberglass Door For Painting?

If you are repainting an old fiberglass door, you need to prepare it for painting. Make sure that the door is clean and ready to be painted. As much as possible, get rid of any dirt or debris and follow these steps when preparing your fiberglass doors for painting:

  1. Remove all door hardware, weatherstripping, and accessories attached to the door. If you do not want to remove them, mask them instead.
  2. Remove the door from the hinges, then let it lay flat on a table or sawhorses.
  3. Place a painter's drop cloth along the door to prevent spills and drips.
  4. Wipe the door with a clean rag soaked in acetone. If acetone is unavailable, you can use other mineral spirits.
  5. Wash the door using a wet rag soaked in mild detergent solution. Afterward, rinse and dry the door.
  6. After drying, carefully sand your fiberglass door.
  7. Remove dust by wiping with a lint-free cloth dipped in acetone.
  8. Let the door completely dry.

After this process, you can now proceed to apply the primer. Use a 4-inch brush going in the direction of the grain or texture of the door. When drying the primer, follow the instructions from the manufacturer before applying the topcoat. It will take at least 2 hours to dry the primer.

What Kind Of Sandpaper Do You Use On Fiberglass?

Interior of a white painted living room with a fiberglass double door

If you want to get that extra shine for your painted fiberglass door, the correct sandpaper will help you get that effect. The best sandpaper for your fiberglass doors is coarse-grit sandpaper. Here are the ranges of grits depending on the level of smoothness you desire:

Sandpaper Grit Size

These are the usual grit sizes used for sanding fiberglass doors:

  • 80 to 100 grits - For rough surface peelings; used to get rid of machine marks
  • 100 to 120 grits - For a fine sanding finish; used to remove gel coat
  • 150 to 220 grits - For a smoother finish, depending on your needs

You can start using sandpaper with the least grits and gradually work with higher grits to get the intended smoothness.

Get this Acroma assorted grit sandpaper on Amazon.

Sandpaper Weight

Aside from grit, sandpaper varies in weight. The grading system of sandpapers is from A to E, which tells you the durability of the sandpaper. Below are the different sandpapers based on their weight:

  • A and B- For light sanding and finishing
  • C and D - For cabinets
  • E and F- For tougher sanding jobs

You can use sandpapers graded D to F, with coarse grits ideal for sanding fiberglass doors.

How To Sand Fiberglass Doors

Sanding your fiberglass doors is a separate and time-consuming process. Follow each step below on how to sand your fiberglass doors:

  1. Leave your fiberglass out under the sun for at least 5 to 6 days. The curing gets rid of air pockets on the gel coating, which causes problems when painting.
  2. Clean the door with a grease/wax remover or paint thinner.
  3. After drying, start sanding the door with coarse-grit sandpaper (range from 100-220 grits).
  4. If you filed too much, fill the deep spots with glazed putty.
  5. Apply the primer to the fiberglass door.
  6. Sand your door with less coarse sandpaper (range from 80-100 grits) for a smooth finish.
  7. Before painting, leave your door again out under the sun after sanding.

Tips When Sanding

To make sure your sanding is effective, remember these tips:

  • Use a respirator or any face cover to avoid inhaling dust and other small particles. Always ensure your safety first.
  • It is best to use your hands rather than a sanding machine, especially when sanding small and intricate parts. The sanding machine can make you lose your flexibility and control when sanding.
  • Sand the surface with the same amount of pressure. The direction when sanding should also be consistent to get an even surface.

What Kind Of Primer Do You Use On Fiberglass?

A gorgeous rustic inspired fiberglass front door

After preparing and sanding your fiberglass door, you can now prime your door. When choosing your primer, you can refer to the product labels for compatible topcoat paints. Choose a primer formulated for exterior surfaces where the bonding of paint is critical. Also, make sure that the primer is good for fiberglass.

Here are the kinds of primers you can use for fiberglass doors:

  • Urethane Primers - for a modern base and clear coats, as well as single-stage topcoats.

Get this Eastwood 2K urethane primer-surfacer on Amazon.

  • Epoxy Primers - for durable resistance to corrosion and wet and humid conditions.

Get this Eastwood epoxy primer with corrosion resistance on Amazon.

  • Latex Primers - for flexible and dry fasting that prevents more cracking.

Get this Kilz high-bonding primer on Amazon.

What Kind Of Paint Do You Use On a Fiberglass Door?

Painting your fiberglass doors adds to the appeal to your entryways. You must choose the right kind of paint for your fiberglass doors for a long-lasting coat. When choosing your paint, make sure that it is for exterior purposes and formulated for fiberglass doors. Also, consider the weather conditions, the sunlight exposure, and the texture of your fiberglass doors before buying your paint.

These are the kinds of paint used for fiberglass doors:

  • 100% acrylic paint
  • Oil-based or alkyd paint
  • Epoxy- or polyester-based paints

If you have textured fiberglass doors, you can also stain them instead of painting them. Staining gives a more natural wood look to your fiberglass doors. Staining is best if you want to match the wood elements of your overall home design.

Regardless if you want to paint or stain your fiberglass door, it must be compatible with your primer. Check out the kinds of paint and stains for your fiberglass door.

In Closing

Priming is an essential step in preparing your fiberglass doors for painting. Even though priming takes time, the benefits will pay off in the long run. Aside from priming, preparing your fiberglass doors for painting involves sanding. Sanding is critical in maintaining the smooth finish of your fiberglass doors.

If you want the best results, choose the paint that is compatible with fiberglass doors. When everything is ready, you can start priming and painting your fiberglass door!

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