Sponge the wall with a detergent-and-warm-water solution. To clean gloss or semi-gloss paint, use a powerful detergent such as trisodium phosphate. It not only removes oil and debris, but it also etches the finish and increases paint adherence.
With a paint scraper, remove any loose drywall mud from seams where the paper is separating. With a scraper corner, puncture bubbles that have developed in the tape. Remove the separated paper using your fingers or a utility knife. With a dry paintbrush, remove any leftover dust and loose muck.
Apply a layer of drywall primer to all areas that require repair. Brush it on or roll it on and wait for it to dry before continue.
Using a 4-inch drywall blade, coat the seams from where you removed the tape with drywall joint compound, or mud. After moistening the paper drywall tape with water, scrape it flat on the mud. Spread a second coat of mud over the tape and smooth it out.
Remove any popped-out drywall nails and replace them with 1 1/2-inch drywall screws. Using a drill and a No. 2 Phillips bit, drive the screw heads about 1/16 inch below the surface of the drywall. Mud should be used to cover the heads.
Apply a layer of mud to any uneven seams where no tape has been removed using the drywall knife. With the knife, flatten the mud.
Allow the initial application of mud to cure overnight before recoating all of the damaged areas. Make a broader seam that feathers out into the wall with a 6-inch knife. Allow that coat to dry before applying a third layer using an 8-inch knife.
Sand all of the repaired areas using 120-grit sandpaper. If the space doesn’t have enough natural light, shine a work light obliquely on the wall to assist you in getting them flat. Protect your lungs by using a dust mask.
Texture the wall to match the existing texture, if it has one. The technique used relies on the pattern of the current material. A knock-down pattern may sometimes be replicated by spraying texture from a can and smoothing it with a drywall knife as it stiffens.

Allow the texture to dry before priming the repairs with drywall primer. When it’s dry, go over them with the wall paint.
What You’ll Need
Sponge
Detergent
Scraper for paint
Paintbrush
Primer for drywall
a roller of paint
Compound for drywall joints
4 drywall knives, 6 drywall knives, and 8 drywall knives
drywall paper tape
drywall screws 1 1/2 inch
Drill
Phillips No. 2 bit
sandpaper 120 grit
Light work
Texture spray
Paint the walls
Tip
If you don’t have a perfect match for the wall color, prime it and paint it with the color you do have.
Repairing damaged seams using fiberglass mesh tape and hot mud can help prevent their recurrence. Cracks, on the other hand, frequently indicate that your foundation is sinking, and they may reoccur regardless of how you fix them.
Warning
Cover the floor with plastic sheeting to avoid a large cleanup effort once you’re through.