How to Sand a Drywall Patch Without Scuffing the Paper

Three coats of mud take a morning and a couple of days of drying, and sanding takes about twenty minutes, so it is the step most often rushed. Sanding is where a drywall repair in Riverside, CA is either finished or ruined, and the sanding described at riverside drywall contractor birchis stops earlier than most people expect, once the edge of the patch can no longer be felt.

Grit and the tool

A sanding sponge or a pole sander with a 120 or 150 grit screen does the work on joint compound. Coarser paper cuts fast and leaves scratches that show under paint. Topping compound sands easily and should be taken down with light passes. Hot mud and setting compound are hard and are better knocked down with a blade first, because sanding them is slow and heavy.

Feathering the edge

The edge of a patch is the part that gives it away. Each coat should be wider than the last, and the final sanding blends the outer rim into the wall with long, light strokes across the edge, never in circles. A circular motion digs a shallow bowl around the patch that catches light for years.

Staying off the paper

The paper face of gypsum board is thin. Once sanding breaks through to the gray core or lifts a fuzzy nap, the paper will swell under paint and show as a rough scab. A wall that reaches that point needs a coat of sealing primer and a thin skim of compound over the damaged paper, then another light sanding.

The raking light check

Turn off the room light and hold a work light against the wall at a shallow angle. Low spots, ridges and sanding scratches show as shadows. Mark them with a pencil and fix only those. Running a bare palm over the surface finds what the eye misses, and the check takes only a few minutes.

Controlling dust in dry air

Riverside air is dry for much of the year, and sanding dust travels far in it. Drywall dust gets into return vents, light fixtures and every flat surface in the house. Closing the door, sealing the vents with plastic, and hanging a damp sheet at the opening cuts the spread. A vacuum with a fine filter, rather than a broom, is the right cleanup, and the wall should be wiped with a barely damp cloth before primer so the dust does not become paste under the paint.