How to Paint an Old Metal Building With an Airless Spray Gun

Dec 01, 2023

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Have you got a tired old outbuilding or shed that is crying out for some TLC? Then why not give it a good old facelift using an airless spray gun?

The process is super easy, and fast, and, dare we say, very fun indeed. Follow this handy guide to find out how to complete this relatively simple DIY task yourself at home.

But, like anything of this nature, we will need some things first.

The first step is to remove any water-damaged or rotten parts of the building. In this case, the main door had become rotten over time from water exposure.

Remove the entire doors and door frame, as needed.

Once complete, tidy up the openings if needed. Then maneuver and place your new doors into place. Hopefully, they fit as snug as a glove, but if not, adjust the door frame accordingly and use packing pieces, etc, as needed.

Secure the door, and frame, to the main building, as needed. Caulk the door frame from the outside to make sure it is watertight going forward.

Next, remove any other fixtures and fittings to the outside of the building you don't want to be painted. Things like gutters and other rainwater goods, trims, etc, should be removed. You could, of course, paint these too if desired.

With that complete, it is now time to clean up the existing structure ready for painting. If your building is metal framed, wire brush of any rust to the envelope. Use a grinder with the right attachments for this.

You'll likely need to focus on the lower levels of the building and any joints/seams between metal sheeting. This will, however, completely depend on your building.

The next step is to thoroughly clean the outside of the building ready to receive the paint. Use a specialist soap and pressure washer to get the job done.

Focus on one side of the building at a time so that you have time to apply the soap, and then remove it before it dries.

Continue until all areas of the exterior have been thoroughly cleaned. Have fun, this is actually quite cathartic.

With that complete, you can now turn your attention to treating any rusted areas of the exterior. Grab your rust treatment product, and treat the rusted areas as instructed.

When that is complete, you may want to also cover any bolt/rivets too to prevent bleeding in the future. This will, of course, completely depend on your building. Don't forget to also treat any seams between metal sheeting, if present.

Leave the rust treatment to dry, as needed.

Next, prepare your exterior paint. In this case, the trims will be painted with a darker tone to match adjoining buildings.

Mix up the paint and add it to your airbrush dispenser as instructed.

Bleed out any air bubbles as needed too before applying. With the airbrush ready, begin to spray paint the areas in question. In this case, the trims, gables, and eaves will be painting using a different tone to the rest of the building.

These were painted first. As these are quite high, the painting was done off a stepladder, so take care to stabilize it first. Consider getting a friend to foot the ladder for safety.

To prevent overspray, use scrap bits of wood, cardboard, or whatever you have to hand, to shield areas as you go.

Leave to dry before moving on to the main sidings of the building.

With the trims complete, it is now time to move on to the main event -- painting the walls. Grab your Graco ProX17, or equivalent, and load with paint as per the unit's instructions.

You could paint by hand using a roller or paintbrush, but the time saved, and final effect, from using an airbrush is far superior for large surfaces like the sides of a building.

As before, bleed out any air bubbles, or water, from the system before beginning to apply to the building. With everything ready, begin to spray paint your surfaces, as needed.

Just like painting by hand, ensure you get an even coating where needed. To prevent overspray, cover over features you don't want to be painted with masking tape, old plastic bags, etc, beforehand.

Don't forget to mask off windows, doors, and other features too like the eaves and soffits (if you don't want to paint them the same color, of course.

Also, and it probably goes without saying, never wear your "Sunday Best" clothes when painting anything. Always change into older, worn-out clothes, or wear protective clothing, as needed.

The use of this equipment will really make a difference for such a large job. For reference, the building this video is roughly 30 feet (9 meters) by 40 feet (12.2 meters) and took less than 4 hours to complete from start to finish.

Continue to use the airbrush until all elevations of the building are complete.

With the painting complete, it is recommended your remove any masking tape/paper/plastic overspray protections off immediately. This will prevent the paint from being stripped off once dry.

You can then touch up the paintwork by hand afterward if needed.

With that complete, you'll be on the hunt for a new project we dare say. How about building your very own handy workbench to stick inside your freshly painted shed/barn?

You are welcome.