How To Stain A Fiberglass Door

Your old or new fiberglass door needs a new finish to match your home, but you’re lost on the exact process of staining? Thankfully, I know exactly how to take an old door (even an ugly new one) and stain it into a great first impression of a room. 

How To Stain a Fiberglass Door

But before you begin staining, there are a few things to consider and plan for.

• Remove the door from its hanging position and set it on a couple of sawhorses. This will make the process easier in the long run.
• Take the hinges off of the fiberglass door to make it easier.
• Remove the doorknob and handles, so you won’t accidentally stain the metal or detailing of the door. 

Ventilation should be a top priority. Stain products carry toxic and heavy fumes, and proper airflow is vital.

However, your staining area needs to be free from heavy winds and dust, so there won’t be any lint or dust particles dried into the stain coat. 

Safety Tips

As with any DIY job, you will need to make sure you prevent injuries and accidents. Always stick to the following when attempting your staining project:

• Work with enough lighting so you can see what you are doing clearly. 
• When removing the door from its hinges, ask someone to help hold the door so that it won’t fall on you or anything else.
• Work in a well-ventilated area to prevent inhaling toxic fumes
• Have a first aid kit on hand
• Don’t leave any stained rags and stained steel wool in direct sunlight because oil-based products may spontaneously catch fire if not properly discarded. Put these items in a closed container with water to prevent fire hazards. 

Tools Needed

To stain a fiberglass door, you will the following tools: 

• Gel stain or an oil-based stain
• Interior or Exterior Clear Polyurethane Finish 
• Mineral Spirits
• 2’’ Natural Bristle Brush
• 2’’ Foam Brush
• Latex or Rubber gloves
• Clean, lint-free cloth
• Stirring stick 
• Extra cleaning rags
• Screwdriver
• Masking tape 

Set up your workstation and tools before you begin staining. Make sure the door is clean of any dust and particles before you begin.

1. Apply Stain with a Foam Brush

Put on your gloves and tape any details on your door you don’t want to stain. Using the foam brush, evenly apply the stain in this specific order.

1. Stain the vertical, raised surfaces in the direction of the grain
2. Stain the inside vertical  panels with the grain
3. Stain the inside panels with horizontal grain
4. Stain the outside panels with vertical grain
5. Stain the outside edges and contours of the door
6. Clean brushes with mineral spirits

While a rag works well when applying to stain to wood, it is not the best choice for fiberglass.

Below is a diagram of the order to stain your door. Not all fiberglass doors look like this one, but use this as a guide for your fiberglass door. 

Image: myoldmasters.com

As you are staining, apply the stain lightly. If you want a darker finish than a light stain application allows, wait 8-12 hours before applying a second coat. 

It’s best to have thinner coats of stain – as this will prevent the fiberglass surface from warping and prevent any sticky and tacky finishes.

2. Remove Excess Stain with a Clean Cloth

Once you’ve even applied your stain, you need to clean any excess:

• After coating the door, remove any excess stain with a clean cloth or rag.
• For the best results, wipe the door in the direction of the grain embossed into the fiberglass.
• This step ensures a consistent and even finish after using the foam brush.

3. Remove Streaks with a Bristle Brush

Sometimes streaks develop after you wipe away excess stain. If this is the case, then follow these steps:

• Gently use a bristle brush to eliminate any streaks or lap marks the foam brush may have left.
• Brush into the corners and crevices to remove any stain accumulations on the edges
• Remove any excess stain from the bristle brush with one of your rags/cloths. 
• Clean all brushes with mineral spirits.

The steps above outline the standard method of staining a fiberglass door. 

4. Protect Stain with a Polyurethane Finish

Your door will most likely be exposed to different elements, like sun and rain. To protect your stain, you need to apply a finish. While there are a lot of finishers to choose from, I recommend using oil-based polyurethane.

• Wait for the stain to dry for 8 – 24 hours.
• Once the stain is dry, you should wait an additional 1-2 days before applying polyurethane.
• Apply the polyurethane with the 2’’ bristle brush in the direction of the grain
• Use a natural bristle brush for oil-based poly, while water-based poly should use a synthetic bristle brush
• Wait at least 6 hours for the polyurethane to dry
• Apply a second protective coat 
• Clean all brushes with mineral spirits.

What Stain Should You Use On A Fiberglass Door?

We suggest a gel stain or oil-based stain with a clear polyurethane finish on top. 

Avoid semi-transparent stains as they will have a ‘streaky’ and inconsistent application. 

Instead, buy high-quality, opaque (non-transparent) and heavily pigmented stain. 

Stain vs Paint A Fiberglass Door?

Staining a fiberglass door may be easier than painting, as the painting process requires some more preparation and priming so that the paint properly adheres to the fiberglass. 

Paint might be a better option if your fiberglass door is exposed to significant exterior weather and conditions. Paint coatings are slightly thicker and are also designed to protect the door from the elements. 

You can use polyester, polyurethane, acrylic and epoxy resin paints to paint a fiberglass door. But avoid oil-based paints, (unlike oil based stains) they can damage the door.

If you’re still debating what  stain or paint to use to coat your door, visit this helpful article on paint/stain types to help you decide.

Conclusion 

Staining your fiberglass door is not difficult, but the details can be in making sure that the stain application looks good.

Depending on your desired finish, the project may take 1-3 days to complete. It’s best to apply light and thin coats of stain and polyurethane – if you’d like a darker finish, you need to apply second and third coats.