Repairing Holes In A Plaster Wall

Older homes with plaster walls often need spot-repairs to fill cracks and holes. Here are tips and instructions on how to do it yourself, including a list of tools and supplies.

Many owners of older homes, fortunate enough to have plaster walls and ceilings, are periodically faced with the task of repairing cracks and holes that develop as the home "settles" and ages.

Other common causes of plaster damage include accidents with furniture, remodeling, and replacing or removing light fixtures.

If you're one of those homeowners peering into a hole in your plaster wall, here's what you'll need to have handy to repair the problem. Keep in mind that re-plastering done quickly or carelessly usually won't achieve the necessary bonding, and you'll likely be peering into a new plaster hole -- in the same spot! -- at this time next year.

You'll need:

1. Spackling compound, paste or powder. With its vinyl or latex base, pre-mixed paste is stronger, easier, less messy and more efficient than the powder for smaller jobs; patching plaster should be used for larger jobs. Be aware that the water-based powder typically hardens, in the pail, into a cement-like substance after a period of time. That renders both the mixture and the pail useless. So if you use the powder, make small batches at a time.

2. Patching plaster, for large holes and big jobs

3. A three-inch-wide putty knife made of flexible steel that's strong enough to apply the pressure you need while it easily "gives" as you force it back and forth, up and down, across the hole you're repairing.

4. A sturdy chisel

5. A metal plasterer's trowel

6. Fine-grit sandpaper

7. Clean, dry paintbrush

8. Small bucket of clear water

If you're patching a very large hole, or a hole that has no backing, you'll need a piece of gypsum board or a piece of flexible mesh wire. These will provide a surface to which your layers of new plaster can adhere.

In either case, the piece of board or mesh must be larger than the hole you're repairing. And you'll need a ruler and cutter to trim the gypsum board to size.

Widen the Damaged Area

In order to achieve a good, strong bond between the existing plaster and the new plaster, you can't simply lay spackling or plaster compound on a wall. On smaller holes, you want to widen the opening sufficiently to allow space for you to press and push the new patch deep into the hole. That way, the patch will bond completely from the inside out.

Carefully insert your chisel into the hole. You want to "undercut" the opening by making it wider on the inside of the wall than it is at the surface.

Chisel away the undercut material a little at a time, brushing away the residual dust and plaster particles as they accumulate.

Wet and Spackle

On smaller holes, use your paintbrush to completely wet the area that you're about to repair. Then dip your putty knife into the spackling compound, scoop up a large amount and begin filling the hole.

Press down as you drag the putty knife back and forth, up and down, making sure the entire hole is filled and packed in as tightly as you can make it. Spackling compound tends to shrink slightly on drying, so be sure to get a tight, solid bond.

When you've completely filled the hole and are certain there's no open space between the old plaster and new, sand the surface very gently to bring the new patch level with the old wall.

For Larger Holes

Follow the process of undercutting the opening even more carefully and remove soft, broken or crumbling plaster wherever you find it. Often, this requires that you chip all the way down to the wall lath, an event that sometimes alarms first-timers. Don't be intimidated by the sight of bare lath!

Once you're cleared away all the old plaster, wet the entire area -- including the lath if that's exposed -- with your paintbrush. Prepare small batches of patching plaster at a time, following manufacturers' instructions on how much water to add. The plaster should be malleable but somewhat stiff and never runny.

You'll apply at least two coats of plaster to the larger holes, allowing the first to dry before applying the second coat. Use your trowel to accomplish this.

Make sure that the first coat completely fills every little opening in the hole, filling the hole halfway to the top. Press as hard and firmly as you can to ensure the lath is completely covered, and that the plaster patch is completely bonding with the old plaster along the hole's inside edges.

For very large holes, you may want to trim the piece of gypsum board to nearly the size of the hole, and then nail the board in to the lath. This will give your patch something tangible to which to adhere, and reduces the amount of plaster required to fill the hole.

In either case, after you've applied the first coat of plaster, use your wire mesh to "rough up" the patch before it dries. Plaster likes a rough surface to bond effectively.

When the first coat is completely dry and hard, use your brush to wet the patch and the surrounding surface. Then begin again to lay on the plaster patching, using the trowel to fill and spread the soft, plastic-like patch until you've reached the wall surface.

Then press again, hard, to be absolutely sure you've left no unfilled crevices or air pockets in the patch.

Smoothing out the final patch isn't difficult. Before the patch is completely dry, use your wet paintbrush again to brush the surface smooth. In your other hand, have the trowel handy to apply pressure to the area you've just brushed. Make sure the patch is wet while you do this, and make sure you've extended the new plaster flush with the old wall.

In the end, you'll have a like-new plaster wall that speaks directly to the quality of your home. So don't moan and groan about the plaster-repair projects. Be grateful that you've got such wonderful plaster walls to repair!

© High Speed Ventures 2011