Ask the builder: Fixing water-damaged drywall

By Tim Carter
Friday, March 18, 2011; 7:02 PM

Q. A water line burst in our home and created a significant leak. We were home and able to contain most of the water, but quite a bit got through the floor, ruining the drywall ceiling in the basement. Is there an easy way to deal with water-damaged drywall? Can we just wait for it to dry and then repaint it? How do you decide whether to replace the drywall? - Susie W., Baltimore

A. I've been dealing for three decades with drywall that has suffered the indignity of getting wet. Sometimes we have saturated the drywall with water on purpose at the job site to get it to bend, but most times a roof leak, foundation leak, plumbing misfortune or chronic condensation has caused the drywall to fail.

I can clearly remember past calls from shocked customers who have lost entire ceilings when, without notice, the drywall crashes to the floor. The weight of the water and loss of structural integrity of the gypsum core causes the drywall panels to tear away from the fasteners. It usually happens at the worst possible moment.

You may not think that much water leaked, but it doesn't take much to create a disaster. The first signs that your ceiling is in danger of falling are depressions around the fasteners. You'll see small dimples form as the drywall surrounding the nails or screws succumbs to gravity and starts to droop, leaving an upside-down crater. If you see this happening, move all valuables and furniture from the room in anticipation of a ceiling collapse.

If a bubble or droop appears in the drywall, water could be ponding on the other side. Use a nail to punch a drain hole, allowing the water to escape. Capture it with a bucket.

Test the ceiling with your fingers. Poke at it. If it seems as hard as drywall that has not gotten wet, you may have dodged the bullet. But if the drywall seems soft or spongy, you're going to be best served by cutting out the damaged section before it sags and possibly falls. Cut carefully, as all sorts of wires, cables, water lines, radiant heating pipes and so forth can be just on the other side.

Repairing water-damaged drywall is not too hard. Ceilings will present the most difficulty if you're not a professional. Working over your head is not easy, and getting the repair to blend in with the rest of the ceiling will be tough to achieve if you're not highly experienced at finishing drywall.

It's best to try to cut out the wet drywall as soon as possible so that you minimize any mold growth. Mold spores are hidden in the typical ceiling; the temperature is perfect, and they have food. The only ingredient missing was water, and now that's present. Mold can bloom within days if you don't act.

Be sure to wear goggles or other eye protection as you remove the damaged drywall. The last thing you need right now is a scratched cornea from a nugget of gypsum falling into your eye.

One of the biggest challenges in getting the ceiling ready for a new piece of drywall is cutting back the water-soaked drywall to the center of one of the ceiling joists. This is accomplished with any number of tools, from a sharp razor knife to a reciprocating saw held at a low angle so the blade just cuts into the drywall and not the wood joist.

You can also cut to the side of a joist and then nail on a scab or sister 2-by-2 that will be the lath catcher for the new drywall. Just be sure the bottom of the framing material is flush with the bottom of the existing joist. If it's lower, you'll end up with an unsightly hump in the ceiling.

-Tribune Media

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