Painting drywall with water damage
If you try to apply paint over surfaces that have been compromised by water damage, the water in the paint only worsens the problem. Before painting drywall with water damage, the damage has to be repaired first.
When you see a water stain on a wall or ceiling, it’s usually a fraction of the actual amount of damage. Finding and correcting the source of that damage is first. Once that’s done, it’s time to assess and repair the water damage.
When drywall gets wet
In drywall, water damage causes:
- water stains
- tape joint failure
- paper veneer lift from the drywall
- crumbling and disintegration of the drywall
- mildew or mold formation behind the wall or ceiling
When water infiltrates a wall or ceiling, it finds the fasteners and tape joints, and that’s its quickest route to being detected. You’ll see screw “pops” and buckled tape. Even after the water has dried, it leaves air pockets. The tape bubbles and lifts away from the previously flat surface.
If you try to apply paint over surfaces compromised by water damage, the water in the paint only worsens the problem. The damage has to be repaired first.
Before painting drywall with water damage, remove furniture, pictures and rugs from the space. Then, put down drop cloth floor protection. Start by cutting out the area where the worst staining is visible.
Peel back and remove tape until you get to a section that’s absolutely solid and intact.
Allow some dry out time after removing the damaged tape joints. The removal process is very messy. Many feet of tape, chunks of drywall, stinky dust, and paper facing must be bagged up and disposed of. Constant vacuuming is a must.
Use joint compound and tape to recreate the joints. You can use either paper tape or mesh fiberglass style tape. Mesh tape is easier to use for repair work because it beds in mud easily and blends well. It’s less likely to show lipped edges through mud.
Before bedding the tape, make sure all loose gypsum and debris is off the surface, so there is no contamination in the new mud. Use a 6-inch mud knife, and skim a layer of mud into the damaged area. Do one section at a time, and immediately lay tape into the area while the mud is still wet. Then, skim your mud knife over the tape in a smooth but firm pass to set the tape cleanly into the bed of mud.
The next step is the first skim. While tape is just over 2 inches wide, it’s often necessary to create a skim that’s 16 to 24 inches wide to perfectly blend a repair joint into its surroundings. It’s helpful to have several knives, with the 6-inch knife the smallest. It also helps to use a “hawk,” which is a large flat plate with a handle, to hold the mud you are skimming.
It’s typical to do as many as three to four rounds of full skimming on a repair job. Keep the skims as thin and smooth as possible to minimize the amount of sanding between coats of mud. Ideally, you are just taking the “edge” off the dried skims before applying the next.
To control dust when sanding, use sanders with dust collection instead of sanding by hand.
Prepare to paint
When taping and skimming is complete, it’s time to apply primer. Using a 9-inch roller and drywall primer, spot prime or “feather” the skimmed areas. This seals the mud and reduces the risk of “flashing” when paint is applied.
Next, apply paint to the primed areas. This blends the repair to its surroundings, from a coverage standpoint, and also helps to reintroduce roller texture to the repaired area. Inspect carefully at this stage. If anything doesn’t look right, skim again, then do the spot prime and first coat paint steps again. Repeat as needed.
Now, the paint job can begin. The repair and touch up is never enough. If the room has any kind of natural light, you can almost always see the repaired areas because the primed/touched up areas look more freshly painted than the surrounding surfaces.
–By Chris Haught
Chris Haught is the editor of Blogging Painters, a website she developed for painting contractors while working as a paint contractor in Southern Utah.