How To Repair Cracks In Plaster, This Old House

Yous just gotta dear plaster. That rock-hard substance, which was applied to the walls and ceilings of well-nigh every house in this state until the 1950s, gives u.s. surfaces that are seamless, mold resistant, fire resistant, and racket dull. But what to do when plaster cracks, buckles, and pops loose? It'southward a perplexing question for many of our readers, including Tim Thorp, whose firm in Providence, Rhode Island, is filled with badly blemished plaster.

"How do I patch 100 years of gouges, cracks, and screw holes and then the walls look flat and clean when painted?" he asks united states of america in an email. Here, Tom Silva shows how to repair plaster walls to brand them look every bit good as new.

Plaster Crevice Repair: An Overview

The key to any ready is to reunite the plaster with the strips of wood lath underneath. Otherwise the cracks come dorsum, no matter how many times you patch over them. That's why This Old House full general contractor Tom Silva usually reattaches lath with screws and metal washers before attempting a repair.

Recently, though, he tried Big Wally's Plaster Magic, a homeowner-friendly adhesive that uses glue instead of screws. While information technology costs more than than the screw-and-washer method—a six-tube kit runs $120, versus $twenty for 120 metal washers—the concluding finishing is easier and looks better because there aren't any washers to embrace. Plus, a glued bond lasts longer than a screwed connexion.

How to Repair Plaster Walls

1. Drill Into the Plaster

Man Drills Hole Near Crack In Plaster Wall

Using a iii/16-inch masonry bit, drill a hole in the plaster about 2 inches from the crack. When you lot hitting lath, cease—the bit won't get through wood—pull out the bit, and drill another hole almost iii inches from the first and virtually 2 inches from the crack. Endeavor to striking a strip of lath with every hole you drill. If you miss, the fleck will sink in correct to the chuck.
Mark such holes with a pencil as a reminder not to inject them with primer or adhesive in the adjacent steps; try drilling over again most half an inch up or downwards.
Keep until there is a series of holes well-nigh four inches apart on both sides of the crack. Vacuum the plaster crumbs out of all the holes.

2. Prime and seal

Man Sprays Acrylic Conditioner Into Holes

Put on rubber goggles and disposable gloves, then spray-pump a stream of the acrylic conditioner into each of the holes (only not into any you've marked). One or two squeezes should be plenty.
Spray the edges of the crack, too, and clean up drips with a moisture sponge. Wait ten minutes for the milk-thin conditioner to soak into the plaster and woods.

3. Inject the adhesive

Man Injects Adhesive Into Primed Holes Of Plaster With Caulking Gun

Place the adhesive tube's nozzle in one of the primed holes. Gently squeeze the caulking-gun trigger until the creamy glue fills the hole and a little backs out around the nozzle.
Practise the same for all unmarked holes. Scrape off the backlog and wipe the wall clean with a wet sponge.

4. Clamp the wall

Skid a 2-inch plastic washer over a 1 5/8-inch drywall screw, and drive information technology into the board through i of the adhesive-filled holes. The screw pulls the lath confronting the plaster's back side while the washer gives the screwhead a broad clamping surface.
Establish washers most eight to 12 inches autonomously on both sides of the crack.

five. Wipe and wait

Man Wipes Off Excess Adhesive From Washers

Wipe away whatever excess adhesive with a wet sponge.
Wait a day or 2 for information technology to cure, then back out the screws and scrape off the washers. (Save them for another plaster-repair project.) Likewise, scrape off whatever dried agglutinative poking out of the holes.

6. Fill up the crack

Man Fills Cracks With Setting-Type Joint Compound

Mix upwards a small batch of setting-type joint chemical compound and apply information technology to fill up the crack and all the holes. Shine the wet chemical compound with a trowel; and so, equally it begins to harden, wet it and smooth it again.
Later the compound sets, sand the area lightly, then prime number and pigment.