How to Plaster Over Drywall
Most modern homes are outfitted with drywall that has been primed and painted. While drywall is a sturdy alternative to plaster, you might want to reinforce your drywall with plaster for stronger walls, greater soundproofing, or an Old World texture. Whatever the reason, the process is always the same. Plastering over drywall requires patience and a steady hand, but an intermediate do-it-yourselfer can complete the task in little time with the right tools.
Step 1 – Preparing Drywall
Before plastering over drywall, you must make sure the drywall is in good condition. Though plaster is strong, the drywall will be the foundation. Therefore, if the drywall is shoddy, the finished wall will be, too.
Readying Old Drywall
If the drywall you’re plastering over isn’t a new construction and is already painted, lightly sand the wall and fill any holes or grooves.
Readying New Drywall
For new drywall, tape all the drywall joints using all-purpose joint compound and an 8-inch spackling-compound knife. Once the compound is dry, even out the surface with sandpaper.
Step 2 – Applying a Plaster Bonder
Once the drywall is dry, you must apply a chemical plaster bonder that will help the plaster bond to the drywall. Because the drywall is covered in paper, applying plaster without a chemical bonder won’t work. Follow the directions on your specific plaster bonder to apply it correctly. Follow all safety precautions the product suggests.
Step 3 – Applying a Base Coat of Plaster
Next, get acquainted with how to use your hawk and trowel. When you’re ready, apply lightweight base-coat plaster over the entire wall. Follow your specific manufacturer’s instructions when mixing and applying the plaster. The base coat should be applied approximately 3/8 inches thick.
Step 4 – Applying the Finish Coat
Using a ratio of 3:1 of quick-set gauging plaster to lime putty, mix the finish coat with a drill and a mixing paddle. Refer to the manufacturer’s instructions when mixing and applying your finish coat. Most coats should be about 3/16 inch thick.
If you want a smooth finish, apply the finish coat the same way you applied your previous coat. However, if you want a decorative texture, you can create that texture now with your trowel.