Learning how to spackle moisture-blocking greenboard properly is a useful skill for home maintenance. Greenboard is used in kitchens, bathrooms, and laundry rooms under wall coverings away from taps. It helps prevent water vapor from penetrating the wall covering, greatly reducing mold and mildew growth in these rooms. Follow these guidelines to successfully spackle greenboard.
Step 1 - Find the Studs in Your Wall
If wall studs are 12 inches apart, the thickness of the greenboard under the drywall is most likely 1/2 inch. For 16-inch-spaced wall studs, the greenboard used should be 5/8 inch thick. Knowing this will help you assess the depth of the hole you need to fill in the greenboard.
Step 2 - Remove Tiles Attached to the Damaged Greenboard
Wipe over the tiles with TSP on a soft cloth, or apply Goof Off adhesive remover to the tile grout. Lift the tiles off carefully, prying gently under tile edges with the putty knife to help detach solidly stuck tiles. Set the tiles aside to be reattached later.
Step 3 - Determine the Exact Size of the Hole in the Greenboard
Slice the green water-resistant paper carefully with the utility knife and peel it back to identify the location and size of the hole. Tape the green paper back out of the way until the repair is completed.
Step 4 - Wipe Off Spackle and Board Dust to Isolate the Hole
Apply warm water to a damp cloth and wipe around the hole to clear it of old spackle, dust and drywall flecks.
Step 5 - Stir and Apply the Moisture-Resistant Spackle
Open and stir the moisture-resistant jointing compound spackle. Apply the spackle to the hole with the large putty knife, pressing it in gently to fill the hole. Spread more spackle out around the edges in as narrow a radius as possible to minimize the sanding area after drying. Allow it to dry for several hours until it is hard, non-sticky, and white.
Step 6 - Sand the Repaired Hole
Put on and adjust your respirator face mask. Use 100-grit sandpaper, followed by 150, then 400-grit to sand the hole down to its optimum level of flush with the surrounding wall surface.
Step 7 - Secure the Green Paper Coating Over the Hole Again
Brush on a thin coat of the liquid wallpaper adhesive over the repaired hole. Pull the green paper over the hole again so the edges match, and press it down with slow strokes of the small putty knife, to prevent bubbles and rips. Allow the glued green paper to dry for one hour.
Step 8 - Reapply the Tiles onto the Wall
Apply tile mastic to the wall surface and reattach the tiles as they were before or repaint the space as needed. Replace any that have cracks or discolored surfaces due to the previous damage to the greenboard. Grout the tiles once they have dried in place atop the tile mastic.