Rough plaster is popular in French Country and Italian Tuscan styles of home decor, but it can be difficult to paint or paper over, severely limiting your design options once you are ready for a change. Smoothing the walls is the best way to prepare rough plaster walls for a redecoration.
Sand the high points of the wall using an 80- to 100-grit sandpaper. The amount of pressure required to smooth down the peaks will vary, so start slowly building up pressure as needed.
Wipe down the walls with warm water and a sponge. Be sure to remove all loose dust and dirt from the walls before beginning your skim coat.
Fill in any cracks in the walls with joint compound and drywall tape. Improperly repaired cracks can reopen and will be difficult to fix if you are hanging wallpaper. Fill the cracks with joint compound and tape over them like you would with a dry wall seam.
Prepare your joint compound. Some people prefer using warm mud for their first coat since it dries faster. If you are using a premixed joint compound, pour it into a long mud pan. If your joint compound needs to be mixed, mix it according to the instructions on the packaging paying special attention to the measurements. Improperly prepared mud can add hours of labour to the job.
Apply the joint compound using a 10- or 12-inch broad-knife. Start at the top of the wall and move horizontally keeping your lines parallel. Cover the entire wall in a thin layer of joint compound and allow it to dry completely.
Apply the second layer of joint compound vertically. Once again starting at the top of the wall, apply the joint compound in a thin layer moving perpendicular to your first layer. It takes several thin layers to completely smooth out a wall.
Sand down any remaining tool marks and irregularities once the joint compound has completely dried. Using an 80-grit sanding block, go over the joint compound to remove any bumps left in the wall.
Apply a coat of primer. If you are papering the wall for wallpaper, use a drywall primer and sealer to make the wall nonporous and help the paper adhere.
You can hang a paper liner underneath wallpaper to help smooth out rough textures. The liner works only on moderately rough surfaces, and small-patterned wallpaper may still show some of the irregularities. If you leave some texture on your wall, crown moulding can effectively divide the space between the wall and the ceiling.