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How to Prime a Wall

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Priming Considerations
Two people applying a coat of primer to an unfinished wall.

Learning how to apply primer to walls might seem like an unnecessary effort because of the additional time needed for your painting project. But priming walls before painting gives texture to the surface you’re working on. This allows the paint to adhere to the primer and produce a good finish on your wall, whether you're going from a light paint color to a dark color or from dark to lighter paint.

  • If the wall surface is porous – such as the paper backing of drywall on an unfinished wall, masonry or wood – your first coat of paint can be absorbed unevenly without a base coat of primer.
  • On walls that are already painted with a glossy finish or when using latex paint on top of an oil-based finish, a new coat of paint applied directly on top might have trouble adhering without a coat of primer for it to hold onto.
  • When painting over a dark-colored wall, a coat or two of primer provides a clean and neutral canvas for a lighter paint color to refresh your room. Because it typically is less expensive than paint, using primer instead of several coats of new paint to conceal dark paint colors and blemishes may lower the cost of your paint job.
Purchase Primer
Four buckets of primer placed on a driveway next to a pickup truck.

Water-based latex primer and oil-based primer are both suitable for priming interior walls. Latex primer is considered an all-purpose primer and is easy to clean up with water. Oil-based primer also has versatility and is the preferred choice for blocking stains, wood tannin and for covering porous wood surfaces.

Be sure to have enough paint primer before starting your project. A gallon of primer will cover between 250- to 400-square feet of surface. Two coats may be needed over heavy stains or tannin-rich wood.

Most primers can be tinted to help ensure good coverage for the finish coat. Bright or deep colors require a tinted primer. A store associate will determine the amount of tint to add to the primer following the manufacturer’s specifications and based on the color of the topcoat being used.

Prepare the Wall
A person using a scraper to prepare a wall for a coat of primer.

Prepare for how to prime a wall by removing any HVAC registers, outlet covers, light switch plates, and nails or other hanging hardware. Then, inspect walls for cracks, holes, dents or other imperfections.

  • Use caulk or a lightweight spackling compound and putty knife to fill and repair any holes or imperfections. 
  • Remove excess spackling with the putty knife. Let dry completely. 
  • Use a small piece of very fine 220-grit sandpaper or a sanding sponge to smooth the repaired areas flush with the surface. 
  • Wipe the walls clean with a damp towel or sponge and allow them to dry.
Cover Other Surfaces
Paint primer, painter's tape, a paint roller and paint tray placed on a drop cloth on a floor.

The next step for how to prime walls for painting is to protect any surfaces that you don’t plan to paint.

  • Use painter’s tape to mask off moulding, trim, windows and the ceiling.
  • Cover the floors with a drop cloth to protect them from paint drips and splatters.
  • Move furniture out of smaller rooms. In larger rooms, move furniture to the center of the room and cover the pieces with more drop cloths.
Dampen Roller or Brush
A paint roller resting in a paint tray with primer.

It is difficult for dry rollers and dry brushes to absorb primer. Dampen your paint roller or brush to get off to a fast start. Use water if applying latex primer. For alkyd- or oil-based primer, use paint thinner or mineral spirits.

Brush out the liquid on a clean piece of cardboard to remove loose bristles. Squeeze out excess from a roller by rolling on cardboard or a towel.

Cut-In Corners and Spot Prime
A person using a paint brush to apply primer on a wall at the edge of the ceiling.

A key technique in knowing how to apply primer to walls is the "cut in." Cutting in is basically outlining the wall with a 2- to 3-inch band around the edges.

Pick your starting point and cut in. Use a 2-inch nylon-polyester paint brush or corner pad to apply primer at all corners or places where walls, moulding and ceilings meet.

Next, brush primer on areas of walls and trim that need special attention. This can include joint compound, patches in drywall and plaster, areas of bare wood exposed by scraping or sanding, and any spots treated with stain blocker.

Safety: Wear plastic safety glasses or goggles to protect your eyes from paint droplets when applying primer.

Roll on the Primer
A person using a paint roller on an extension pole to apply primer to an unfinished wall.

For the larger spaces of the wall, apply primer using a 9-inch paint roller with a 3/8- to 1/2-inch high quality roller cover. 

  • Fit the moistened roller cover onto your paint roller. 
  • Stir and pour the mixed primer into a paint tray.
  • Dip the roller into the primer, making sure it’s completely covered.
  • Pass the paint roller over the ridged area of the paint tray a few times to remove excess primer.
  • Start with a single vertical strip at the cut-in corner.
  • Apply the primer in 3- x 3-foot sections. With a fully loaded paint roller, work top to bottom, rolling back and forth across the wall in a series of V- or W-shaped strokes until the section is covered.
  • Roll in one section at a time, moving from high to low and from one side of the wall to the other.
  • Reload your roller and move to the next section, covering only as much as you can finish while the primer is still wet. Always overlap areas of wet primer.
  • If a second coat of primer is necessary, apply it after the first coat has dried according to manufacturer’s instructions.
Sand Primer
a person wearing a dust mask using a sanding block to smooth a coat of primer on a wall.

The last part of how to prime a wall is to smooth out the surface to prepare for its coat of fresh paint. The drying time for primer varies depending on a number of factors, including temperature, humidity and air circulation. Follow the manufacturer's guidelines on the side of the primer can.

  • After the primer dries, lightly sand away bumps and ridges using very fine grit sandpaper folded into quarters.
  • When the grit of one section of sandpaper becomes covered with dust, switch to an unused section and continue.
  • Wipe the wall clean with a damp towel or sponge and allow it to dry before painting.

Priming a wall is the first phase of your painting project and leads to better results. This base coat enables better topcoat adhesion for an even finish on your wall. When you're ready to start your project, shop online for the supplies you need to prime a wall. The Home Depot delivers online orders when and where you need them.