Why does a ceiling stain show up long after the rain stops?
Water moves through the attic, the insulation and the top of the drywall before it reaches the visible surface, so the stain can appear hours or days after the water entered. A stain is the final sign of a wet area, not the first.
Insulation holds water like a sponge, and it can carry the water away from the entry point before the water drips. The drywall absorbs moisture and softens, and when it has taken enough water it discolors and sags. The stain is the point where the wet area has reached the surface.
This is why a dry-looking ceiling can still hold moisture above it. The crew reads the cavity, not only the surface, and the readings show whether the ceiling is drying or still holding water.
When does wet drywall have to come out?
Drywall that is sagging, crumbling, soft or saturated usually has to be removed, because it cannot be dried back to a firm, sound surface. Drywall that is only stained and firm may dry in place if the readings show it is responding.
Drywall that has soaked up water loses its strength, and the gypsum core can break down. Once it sags, it does not return to its original shape, and it is generally removed to allow the cavity to dry. A removal leaves a clean edge for the repair later.
The technician explains the decision with the readings in hand. A material that reads wet in the core and sags under light pressure is removed. A material that reads dry at the surface and is firm can often be left in place.
Is it safe to stay in a room with a wet ceiling?
Not if the ceiling is sagging, cracking or dripping in a way that could fall. Move out of the room and keep away from the area until the crew has assessed it. A stained but firm ceiling can be used normally, but avoid the area beneath any sag.
Falling drywall is a real hazard, and a heavy wet panel can injure someone without warning. If a ceiling is bulging or cracking, clear the room, and tell the crew before anyone returns to it.
Do not use the room's light fixtures or ceiling fans while the ceiling is wet, because water can reach the wiring. Keep children and pets out of the room, and turn off the power to any fixture in the wet area at the panel.
Do I need to repair the roof before the ceiling can be dried?
The roof should be repaired so that no more water enters, but drying can begin while the repair is planned. The crew dries the ceiling and the framing, and a roofer is responsible for the roof. Ask the roofer to inspect the entry point and record the repair.
Drying a ceiling while water is still coming in is slow and often fails, because the moisture keeps arriving. Ask the roofer to stop the leak as soon as the weather allows, and the crew will time its readings with the roof repair.
A roofer is the right trade to inspect and repair the roof. The crew can point out where the water entered the attic, and it can give the roofer the readings and photographs to help locate the damage.
What should the repaired ceiling look like when it is finished?
A repaired ceiling is closed up only after the framing and the insulation have reached their dry targets. The new drywall is installed and finished by a contractor, and the crew confirms the dry readings before the finish work begins.
Once the framing is dry, the new drywall, insulation and finish can be installed. Ask for the readings to be recorded before the new surface is closed, so the dry state of the cavity is on file.
A new finish should be matched to the rest of the room where possible, and the crew can recommend a painter or a finishing contractor. The repair is separate from the drying, and it is quoted after the structure has tested dry.