Tips on how best to patch a wall

If you are planning to paint or to hang wallpaper, now is the time to examine your walls and ceilings and undertake the appropriate repairs. 

• Walls and ceilings built after the 1940s are likely to be made of wallboard, also known plasterboard.
• Such walls are put together from rigid factory-made sandwich panels that are nailed to interior framing.
• Typically 1.2 m (4 ft) wide, their seams and the nail heads holding them in place are covered with special tape and a plasterlike mixture known as joint compound.
• Older, solid-plaster walls consist of several layers of true plaster applied wet on-site over a backing of wire mesh or wooden laths.

• Before you set out to repair problem walls or ceilings, know your limitations.
• Minor cracks and holes left by picture-hanging nails are easy to handle for someone new to do-it-yourself repairs. But anything larger takes more preparation and a more practiced hand.
• For tiny cracks and holes in plasterboard walls or ceilings (one cm,/1⁄2 inch or smaller), clean out the opening, apply spackling compound with a joint knife, allow to dry and sand smooth.

• Sometimes a section of drywall joint tape used to cover joint seams is peeling away. Repairs to this are easy:
• Cut away the loose tape and brush clean the area. Cover the open seam with fibreglass mesh tape cut precisely to fit. Smooth the tape as you go to make a perfectly flat seam. Press the tape to the wall so it adheres.
• Apply a thin, even layer of joint compound with a 12.5 cm (5 in) flexible joint knife to cover the fibreglass mesh tape. Allow to dry. Sand lightly.
• Use a 20 cm (8 in) joint knife to apply a second thin coat of compound over the first. Feather the edges of the joint compound outward, decreasing the thickness of the application as you go, so that the tape margins merge smoothly and invisibly into the surroundings. Allow to dry. Sand lightly.
• Repeat with a wider 25 cm (10 in) joint knife to add a third coat, feathering the edges as before. Allow to dry. Smooth the final coat with a dampened sponge.

• Solid plaster walls require different repair materials and a different patching technique. Patch holes up to 15 cm (6 in) across with patching plaster (in powdered or pre-mix form and different in composition from Spackle or drywall compound). For larger areas of damage, hire a professional.
• Begin by cleaning loose plaster from the cavity, including between lath strips at the back of the hole. Staple a piece of hardware cloth to the lath for better surface grip.
• Dampen the area, and use a joint knife narrower than the hole to apply the patching plaster in three shallow coats. Let each coat dry before applying the next.
• Apply wallboard joint compound for the final coat. This time, use a joint knife wider than the patch, and feather a final, very thin layer of compound. Let dry. Sand until smooth.

• Painted walls can develop chipped or peeling areas.
• Before fixing, make sure to fix whatever caused the problem.
• Then patch the area before you repaint or paper.
• Use a wire brush to remove light flaking, or a broad joint knife for larger areas — taking care not to gouge the plaster surface beneath, which will require a coat of spackling compound to repair the damage.
• Sand the scraped area until perfectly smooth.