An entry doorway is a high-trafficked area and it is not surprising if even sturdy fiberglass entry doors can have cracks. Fortunately for you, this minor damage can be fixed at home using materials bought from a hardware store and some tools you likely already have at home.
Clean and Strip the Cracked Area
Some cracks are visible; some are not. However, if you are sure that the visible crack is the only crack that you have to treat then you have to create a perimeter on the area that you will work on so as not to scratch nearby areas. Even if there is only a single crack to work on, this is also the best time to do a repainting job. Decide on these two before proceeding.
For small cracks, clean the cracked area with mild detergent and strip it of paint using a stripper. Next, isolate the area by creating a perimeter using masking tape and old newspaper. Cover nearby areas with the newspaper too.
Follow the same steps if you want to repair the cracks and do a repainting too (of the entire door).
Patch the Crack
Sand the area starting with coarser 100-grit sandpaper. If the crack is wide, sand the inside too.
Mix the epoxy resin kit by following the packaging instruction. Apply it to the crack using a small spatula, popsicle stick, or a tongue depressor. For very small and thin cracks, use a toothpick to push the epoxy resin down in the crack. Wipe excess epoxy. Let it cure.
When it hardens, get the 200-grit sandpaper and even out the surface. Make sure that the epoxy is flushed with the surface.
Rent a compressor paint sprayer and read the instruction on how to use it. Apply primer on the area in a thin coat. Allow it to dry for a few minutes before spraying another coat of primer. Sand it again to even out the surface. Brush the area to remove powdery residue left from sanding.
Purchase an acrylic paint that matches the old paint in color and texture. If you are repainting the entire door, however, you can select any color you want.
Apply the first coat thinly and evenly. Allow it to dry. Sand it using the 400-grit sandpaper. Apply the second coat thickly. Let it dry.
Apply wax on the newly painted fiberglass entry door. Attach the buff pad to the rotary tool. Turn on the tool and polish the surface in a circular motion. Apply another coat of wax and buff it in the same way. Then stand back and admire your handiwork.