Drywall Repair: When to Patch and When to Replace

Drywall takes a beating. A doorknob swings into it one too many times, or a slow leak upstairs leaves a brown ring on the ceiling. Most of that can be fixed without tearing anything out. Some of it can't.

The question we get most about drywall repair is whether the damage can be patched or whether that piece has to be replaced. Here's how we decide, and which jobs you can reasonably handle yourself.

Small Holes, Dents and Nail Pops

Nail holes, screw holes, shallow dents and hairline cracks are always a patch. Fill them with joint compound or lightweight spackle, let it dry, and add a second thin coat if the first one shrinks. Sand it flush, then prime the spot before you paint. USG, the company behind Sheetrock, finishes every small repair in its drywall guide the same way: sand and prime when dry.

Nail pops look worse than they are. That round bump is a fastener that has backed out of the stud. Drive a new drywall screw an inch or two away to pull the board tight, set the old nail back in, and cover both with compound. If you just mud over the bump, it tends to come back.

Doorknob-Sized Holes

A hole a few inches across is still a patch job. Most repair kits come with a self-adhesive mesh patch, often 4 by 4 inches, that sticks over the hole. You cover it with a couple of thin coats of compound and feather each one a little wider than the last so the edges disappear.

Once a hole gets wider than about 4 inches, it's time to stop patching over it and cut in a new piece of drywall instead.

If a doorknob made the hole, put a door stop on before you fix it. Otherwise you'll be patching the same spot again before long.

When to Replace Drywall Instead of Patching It

Replacing drywall doesn't mean redoing the whole wall. You cut the damaged area out as a neat rectangle, back to the centre of the nearest studs, add wood backing where there's no stud to screw into, and fasten a new piece in the opening. The seams then get taped and finished with two or three coats of compound.

Replacing a section is the better call when:

• The hole is bigger than about 4 inches, or the edges keep crumbling as you trim them
• The paper face has torn away and the gypsum underneath is soft or powdery. USG's guide says crumbly gypsum must be replaced.
• The board got soaked and didn't dry out within 48 hours. CMHC's flood cleanup advice is to remove wet drywall that can't dry in that time.
• A ceiling is sagging or feels soft when you press on it
• Mould has spread past a few small spots. CMHC treats fewer than three patches, each about a square metre, as a small problem you can clean yourself if you're in good health. More than that should go to trained people.

Water-Damaged Drywall

Water damage is the one drywall repair you shouldn't rush. If the leak is still active, you need a plumber or roofer first. A patch over a live leak is money down the drain.

Once everything has dried, press on the stained area. If the board is firm and it's only a stain, it usually needs a stain-blocking primer and paint, nothing more. Plain paint over a water stain tends to let it show through again. If the board is soft, swollen or falling apart, it comes out, along with any wet insulation behind it.

This is where a Home Inspector's habits help. Pedro spent 15 years doing home inspections, and he treats a ceiling stain as a symptom. We find where the water came from before we fix the drywall, so the new patch doesn't end up with a brown ring of its own.

Older Homes: Test Before You Sand

If your home was built before 1990, slow down before you sand or cut. Health Canada says asbestos was mainly used in buildings before 1990, and it lists plaster, drywall and spackling among the older materials that may contain it.

Those materials aren't a significant health risk while they're left undisturbed. The problem is the dust from sanding, cutting, drilling or scraping. Health Canada's advice is to have a professional test for asbestos before you renovate, and to hire a qualified removal specialist if it turns up.

When to Call a Pro

Filling small holes is a fair weekend job if you're patient with thin coats and sanding. It's worth calling someone when a section has to be cut out or when water was involved. Ceilings are harder too, since getting a flat finish overhead takes practice.

With us, small repairs like a drywall patch usually run $75 to $200. Mid-sized jobs such as water-damaged drywall tend to land between $200 and $600. Every job starts with a free written estimate, and a photo of the damage helps us quote it. Call (289) 928-5689.