How to Repair a Dented Metal Door
Many homes have steel entry doors due to the fact that they are secure, thermally efficient, and come in a wide range of styles. Some models even have an embossed wood-grain pattern that can be stained. Steel doors typically cost less than wood or fiberglass doors and are not prone to warping as some wood doors are, especially if they are not covered.
The flip side of metal doors are that they dent fairly easily if struck by a hard object, such as shoes, a rock thrown by the lawnmower or a ball. They can be easily repaired with patching compound in less than two hours.
You should never repair a dented door with spackle or wood putty since neither material will bond very well to the metal. The best choice for a patching compound is to use auto-body filler that is specifically formulated for adhering to metal surfaces. This type of filler also dries hard and sands smooth and flat. This will be the best match for the metal surface and it will last for the life of the door.
Tools and Materials
Acetone or rubbing Alcohol
Auto-body filler, such as Bondo or door dent repair kit
Masking tape and paper
Spray on primer
Paint to match door
Step by Step
1. Sand the dented area down to bare metal with 100-grit sandpaper. Be sure to remove paint from deep crevices.
2. Clean the sanded area with a soft, clean cloth dampened with either acetone or rubbing alcohol.
3. Follow the directions on the body filler - Squeeze out a bead of hardener beside the body filler. Blend the two with a putty knife.
4. Use a 6-in.-wide plastic spreader to apply the filler to the dent. Be sure to slightly overfill the area.
5. Smooth the patch first with 80-grit sandpaper on a rubber sanding block, then switch to 150-grit paper.
6. Mask off the repair area with sheets of newspaper, and then apply two light coats of a metal or rust-inhibiting primer.
7. Use 400-grit wet/dry sandpaper to sand the patch until smooth. You may wrap the sandpaper around a sanding sponge for a more uniform finish and to make it easier to hold.
8. Brush on two light coats of a high-quality enamel trim paint, allowing the paint to completely dry between coats.
You can purchase Bondo Auto-Body Repair Kit at most hardware stores, home centers and auto-supply shops. The cost is usually under $10.
Auto-body filler must be applied to bare metal, and after sanding down the area with 100-grit sandpaper, lightly wipe down the entire area with a clean cloth dampened with acetone or rubbing alcohol.
Preparing the Body Filler
Auto-body filler is a two-part resin that must be mixed with hardener before it can be applied. Keep in mind, though, once the filler is mixed; you've only got about four minutes to fill the dent before the resin begins to harden. It can be tricky to work on a vertical surface, but the filler will be fairly stiff after about a minute. If you aren’t comfortable working in the position, you may want to remove the hinge pins and lay the door flat on the ground or on a pair of 5 gallon buckets.
Sanding the Dent
Mix about 8 tbs. of the gray filler with about ½ tsp. of the red hardener on a scrap of plywood or hard cardboard. Gently knead the tube of red hardener prior to adding it to the filler. Thoroughly mix the two components with a putty knife for no more than one minute. The color should be pink with no gray or red streaks.
Mixing the Body Filler
Apply the filler with the plastic spreader across the dent, forcing it deep into the crevice. Overfill the dent slightly and then feather out the filler beyond the dent by an inch or so all around. Very large or deep dents will require at least two applications.
Spreading the Filler
After 30 minutes check to see if the filler is fully cured, if you can scratch it with your fingernail, wait another 10 minutes. While wearing a dust mask, begin smoothing out the filler with 80-grit sandpaper on the rubber sanding block. Continue sanding until all the high spots are removed and the filler begins to blend in with the surrounding surface. Switch to 150-grit sandpaper and finish-sand the entire patch.
You find a low spot or two after the initial sanding. If you notice this, prepare another batch of filler and spread a thin coat across the surface. When this coat has fully cured, lightly sand the surface with 150-grit sandpaper.
After you have the dent filled and sanded, apply a primer paint coat made specifically for metal. Choose either a rust-inhibiting automotive primer or a brush-on metal primer. Mask off the area around the repair with newspaper. Apply a thin primer coat and let it dry. Repeat if necessary.
When the primer is dry to the touch, remove the newspaper and smooth the primed area with 400-grit wet/dry sandpaper.
Thoroughly dry the door, and then brush on two light coats of an exterior-grade paint. You may want to paint the entire door to prevent the patched area from standing out.
Painting the Patch
Repairing a dented metal door is relatively easy and improves the first impression of your home when friends and neighbors stop by.