Symptoms
- Patched area sticks out slightly or sits recessed compared to the wall around it
- Visible ridge or shadow line at the patch edges even after sanding
- Compound alone can't seem to make the patch flush
Likely causes
- CommonReplacement drywall is a different thickness than the originalCommon drywall thicknesses are 1/2 inch and 5/8 inch, and mismatching them creates a step.
- CommonSupport strips behind the patch installed unevenlyIf backing isn't flush, the patch piece won't sit at the right depth.
- PossibleOriginal wall has an unusual or older non-standard thicknessSome older homes used drywall or plaster thicknesses that don't match modern standard sizes.
What to do
- Measure the thickness of the existing wall drywall before buying a patch piece.
- Purchase a patch of matching thickness, or shim a thinner patch to match depth.
- If the patch is proud (sticking out), sand it down carefully to be flush.
- If recessed, build up with extra layers of joint compound rather than trying to move the patch.
- Feather compound wide, at least 6–8 inches beyond the patch edges, to hide any remaining step.
- Let dry, sand, and apply additional thin coats until flush.
- Prime and paint once the surface reads flat and even.
Tools and parts
- Tape measure
- Taping knife
- Sandpaper
Drywall patch matched to thicknessSearch: “1/2 inch or 5/8 inch drywall patch”
When to call a pro
Call a drywall finisher if the mismatch is significant, since building up or shimming a patch flush takes experience to do invisibly.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.