Stucco broken at the bottom of the wall after a patio or slab came out

Pulling out an old concrete patio, stoop or slab almost always takes some stucco with it. The concrete was often poured right against the wall, sometimes over the bottom edge of the stucco, and when it breaks away the bottom few inches of the wall come off too. What is left is a ragged edge with black paper, wire lath, or bare wood sheathing showing along the line where the slab used to be.

That is not a cosmetic chip. On a framed Pueblo house the stucco is a skin over a weather barrier, and the part you can now see is the barrier itself, at the bottom of the wall where the framing sits on the foundation.

What to do this week

1. Cover the opening. Tuck plastic sheeting or housewrap up under the broken stucco edge, not over it, so water from above runs down the outside of the sheet. Tape or batten it at the bottom. Pueblo’s afternoon storms run through the summer and the freeze season follows, and either one can soak an exposed sill plate.
2. Press on the wood. Push a screwdriver tip into the sheathing and the bottom plate where they show. Firm wood is good news. Wood that is soft, dark or crumbles means water was getting in long before the patio came out, and the framing needs to be looked at before the stucco goes back.
3. Look at the edge above. Tap the stucco a foot or two up from the break. A dull, solid sound is fine. A hollow, drummy sound means the stucco above is loose too, and the repair has to start higher. Our hollow and blistered stucco page covers that sound.
4. Decide what replaces the patio. If new concrete, pavers or gravel are going in, the finished height matters. The base of the stucco has to sit clear of it, so settle the new grade before the wall is rebuilt.

Why it was probably wet already

A patio poured tight against the wall, common on older houses, covers the bottom edge of the stucco. The International Residential Code, section R703.7.2.1, calls for a weep screed at or below the foundation plate line on exterior stud walls, placed at least 4 inches above earth or 2 inches above paved areas, so water that gets behind the stucco can drain out. A slab poured over that line buries the drain. If the stucco along the old patio line came away soft, crumbly, or with rusted lath, that is the reason.

How the base gets rebuilt

This is patching, done from the bottom up:

• Cut back the broken edge to sound stucco, in a straight line, so the new work meets something solid.
• Paper, two layers of weather-resistive barrier, lapped under the existing paper above so water sheds outward, never behind.
• Weep screed fastened at the foundation plate line, at the clearance the new grade allows.
• Lath fastened through to the framing, then the scratch and brown coats, cured between coats.
• Finish coat matched to the rest of the wall. The bottom of a wall is where a color or texture mismatch is least noticed, but it is still worth getting right; our color and texture matching page explains how.

Typical patching jobs run $500 to $2,000, with longer runs along a wall at $8 to $15 per square foot. Any rotted sheathing or sill plate is carpentry, priced separately, and it gets fixed before the stucco goes back on, not covered over.

What to send us

Photos of the whole length of the damage, a close-up of what is showing behind it, and a note on what is going in where the patio was. Tell us whether the wood felt firm. From that we can tell you whether it looks like a straightforward base patch or whether the framing needs checking first.