Wet drywall after a leak: cut it out or dry it in place

Fix the source before the drying starts or you are drying a wall that is still being wetted. Turn off the breakers for any outlets or switches in the wet wall; water inside a cavity reaches boxes before it reaches you. Pull the outlet covers and look; a wet box or a scorched wire is an electrician before anything else.

Score the caulk line with a utility knife, work a pry bar behind the baseboard against a scrap block, and number each piece on the back as it comes off. Wet MDF baseboard swells and will not go back; wood usually will. Pull the tack strip if there is carpet; our wet carpet guide covers the floor. The gap at the bottom of the drywall is now exposed, and it is your first vent.

Drill 1/2 to 3/4 in holes through the drywall about 2 in above the floor, one between each pair of studs (every 16 in), low enough that the baseboard will cover them later. If the drill meets resistance an inch in, stop; that is the sole plate or blocking. The holes let the air movers push dry air across the back of the board, which is where the water is. On a tiled or papered wall that cannot breathe, cut a 4 in strip along the bottom instead.

Shut doors, tape plastic over the HVAC supply and return in that room, and start the dehumidifier with its hose to a drain before any fan runs. Fans evaporate water into the air; the dehumidifier has to be ready to take it out or you are moving the moisture to the next room. A consumer 50-pint unit handles one small room; a flooded basement wall or a whole floor wants a commercial LGR, and the drying planner sizes it from the room volume.

One air mover per 10 to 16 linear feet of wet wall, near the wall and angled 15 to 45 degrees to it so the airstream skims the surface and the vent holes, all pointing the same direction around the room. Do not aim a fan straight at the wall; it stalls the air and pushes moisture into the cavity. Low-profile units like the Velo Pro sit at the base of the wall and feed the holes; the drawing below shows the layout.

Same points, same meter, same setting, same time each day, and photograph the display against the tape. Readings should fall every day. A point that has not moved in 48 hours has something behind it the air is not reaching (insulation, blocking, a double layer of board) and that section gets cut. The wall is dry when every point matches the dry standard within a point or two and holds there the next day; clean-water walls with an empty cavity usually get there in three to five days.

Leave the dehumidifier running two more days while you patch the holes with setting compound, prime any staining with a stain-blocking primer, and caulk and reinstall the numbered baseboard. Keep the meter readings and photos; they are the record that the wall was dried if an adjuster, a buyer or a tenant asks.

Breakers off for the wall. Respirator, gloves and goggles on; drywall dust and anything growing behind it both belong outside your lungs. In a house built before 1978, paint may contain lead, and joint compound and textured finishes from before the mid-1980s may contain asbestos; test before cutting, and if either comes back positive the removal is a licensed abatement job. For Category 2 or 3 water, hang plastic over the doorway so the room is contained.

Take the highest wet reading from your grid and add 12 to 24 in. Then round to a height that makes the repair easy: 16, 24 or 48 in from the floor lands the new piece on a standard sheet dimension, and 24 in is the most common flood cut on a clean-water basement or supply-line loss. Snap a chalk line the full length of the wet wall; a straight cut is a straight tape joint later.

Score along the line with a utility knife in several passes, or run an oscillating tool with the blade set to no more than the thickness of the drywall (1/2 in on most walls, 5/8 in on garage and fire-rated walls). Wires, pipes and the occasional gas line run an inch behind the board. Never plunge a circular saw into a wall. Snap the board along the score and cut the back paper.

Back out the screws or pry the nails, pull the lower section off in manageable pieces, and bag it. Photograph the open cavity before you touch anything inside it; it is evidence of what was wet and why. Remove the baseboard, and any tack strip or wet carpet pad, at the same time.

Wet fiberglass batts come out to above the wet line, which is usually higher than the cut because the batt wicks; cut the batt square and bag it. Wet cellulose is scooped and vacuumed. Pull any polyethylene behind the board so the framing can breathe. The cavity is now open framing from the plate to the cut line.

Wet-vacuum standing water out of the plate channel, wipe the studs and plate with clean water and a detergent, and vacuum again with a HEPA vacuum. For Category 2 or 3 water, apply an EPA-registered antimicrobial according to its label after cleaning; the label governs dwell time and surfaces. Bleach is not the answer on framing: it does not penetrate wood and its water content feeds what it does not reach.

Air movers along the open wall and the dehumidifier in the room, run continuously, with the pin meter in the sole plate and the bottom of each stud every 24 hours. Framing reads about 8 to 14 percent when dry and is wet above 16; wood above roughly 19 to 20 percent can support growth. Sole plates are the slow part because they sit on the slab; expect three to five days for the plate after the studs are done.

New insulation, new drywall cut to the line, tape and mud, stain-blocking primer, paint, baseboard. If the wall is below grade and got wet from the outside, fix the outside first; the 72-hour basement guide ends with the prevention list.