Water leaks typically cause some interior damage, ranging from stains to structural problems. Some repairs are fairly easy to do. Others, especially if damage is extensive,are best left to experts.
As detailed in Dealing with Mold, mold is often a concern when there's water damage. Mold can be cleaned off some surfaces. However, if there's extensive mold growth inside of walls and other materials, it's best to remove these materials and rebuild these areas.
Sagging drywall is damaged drywall. You can remove and replace it, or install new sheets in front of the sagging panels. Unless you've worked with drywall before, this is best left to the experts. If you're concerned about mold, or you've spotted mold growth, have the drywall removed and replaced.
Patching Plaster and Drywall
Water can make these materials swell and crumble. If the damage isn't extensive -- you're seeing small holes and cracks -- patching is fairly easy to do. Ready-mixed spackling compounds, which come in small tubs, work well for this. Use a putty knife to apply the material to all damaged areas. Wipe away the excess with a damp rag or sponge and let dry. If the product shrinks when it dries, apply another coat. For larger holes or cracks, it might be necessary to patch first with a layer of fiberglass mesh tape to provide support. Apply the patch over the tape.
Larger repairs typically require some structural work, and are often more than homeowners want to tackle on their own. If you're in this category, you'll want to call a drywall contractor or handyman.
Water damage typically causes streaks and blotches on walls and ceilings that range in color from dark yellow to brown. They're caused by substances in the drywall or plaster that have leached to the surface. If the surfaces themselves aren't damaged, you can paint over these stains. But you'll need to seal the area first to prevent further leaching.
Wash the area with either a detergent solution or a product designed for cleaning paint. Trisodium phosphate or TSP works well. (For more on TSP, turn to Dealing with Mold). Try to remove as much of the stain as you can without soaking the surface. Let the area dry for a couple of days. Next, apply a stain-blocker primer or sealer. You can find it at paint, hardware, and home improvement stores. When it's dry, go ahead and paint.
Water Damage to Woodwork
If painted surfaces are blistered or peeling, you might have to remove the paint with a paint stripper. Follow label directions carefully. If they're just dulled or stained, sand them lightly and apply an enamel undercoat. Let it dry thoroughly, then sand the area again. Wipe the area clean, and then paint.
Minor damage to varnished wood can often be repaired by lightly sanding the area and applying a new coat of varnish. If the damage is extensive, you might have to remove the varnish, sand the wood down to smooth out the damage, and refinish.