Drywall mud is a mixed compound consisting of gypsum dust and water. The consistency is similar to that of cake frosting. Drywall mud is commonly used to seal joints to create a smooth base when creating walls.
Drywall mud is capable of sticking to concrete; however, it does degrade over time. This is due to the moisture that arises from the bonds of the compound and the concrete. In hot, humid climates, drywall mud can last much longer when stuck to concrete walls.
This article will explain if drywall mud can stick to concrete and how to stick drywall mud to concrete.
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Can Drywall Mud Stick to Concrete?
Drywall Mud will stick to concrete for a while, but over time, moisture from the concrete degrades the bond interface between the water-soluble joint compound and the concrete, causing the joint compound to slide away.
As a result, condensation is a problem. Condensation quickly collects at the bond contact because the joint compound is relatively moisture permeable. There isn’t necessarily pouring wet condensation here, but rather dampness.
Of course, while concrete is water-proof to liquid water, it is relatively porous to vapor. As a result, moisture at the bond interface is more likely to occur in concrete of poor quality, and this causes bond breakdown to happen more quickly.
How To Stick Drywall Mud to Concrete Wall
These instructions will show you how to finish your new wall with tape and drywall mud easily:
1. Bed the Tape and Smooth Out the Compound
It would help if you learned how to correctly bed the tape and feather out the compound to an invisible edge. The other important skill you need at this stage is sanding. Because the joint compound is soft, the issue is to avoid removing so much that the paper tape frays or tears.
2. Mix the Compound and Prepare the Surface
With a tool knife or tin snips, cut the band on top of the bucket and take off the lid. If water is on top of the compound, use a 12-inch (30.48 cm) drill to toss a mixing paddle in. Slowly incorporate in the water until the compound is smooth. The compound is ready to use if there is no water present.
Look for any screw heads peeking through the walls and drive them in until they are slightly recessed. To avoid particles of drywall ending up in the compound, tear away any loose or torn paper from the drywall (particularly around corners and cut edges).
3. Fill Screwheads and Joints
You should fill the mud box halfway with the compound using a 5-inch (12.7 cm) knife and then apply roughly 2 inches (5.08 cm) of the compound to the knife blade’s edge. Next, force the compound into the joints between the sheets starting in one corner of the room.
You need to hold the knife at a 25-degree angle to the surface and smooth out the compound in one stroke until they’re filled. Scrape any extra compound from the knife into the mud box. With a swipe of a compound-loaded knife, fill screw holes. Ensure you check that all joints and screw-heads are completely filled.
4. Apply the Tape to the Wall
You should aim to remove 3 feet (36 inches) of tape from the dispenser without tearing it. Remember to center the tape over the seam and carefully press it into the new compound with your fingertips. Unroll the tape and place it over the remainder joint. Ensure the knife edge is placed perpendicular to the tape face at the end of the joint and tear.
5. Smooth Out the Tape
You need to hold the 5-inch (12.7 cm) knife against the tape at a 25-degree angle to the wall halfway along the joint. In a single stroke, pull the knife to one end of the joint, smoothing the tape and pressing it firmly into the compound.
Scrape the blade’s excess compound into the mud box. Return to the beginning and repeat the process in the opposite direction. (Using this method, the tape will not pull away from the wall.) You need to repeat the 3rd, 4th, and 5th steps on any remaining walls or ceiling.
6. Seal the Inside Corners
Fill the seam with compound and cover 2 inches (5.08 cm) on either side of the corner with compound using a 5-inch (12.7 cm) knife. Cut a piece of tape the length of the corner and fold it lengthwise in half. Gently push the knife into the corner.
Draw the knife along the drywall, starting in the center and smoothing the tape on one side of the crease. Squeeze out extra mud by turning the blade 45 degrees and on the opposite side of the crease, run the knife in the same manner. Return to the beginning point by smoothing.
7. Seal the Exterior Corners
Make sure that every 10 inches (25.4 cm), the metal corner bead on the outside corners is fastened or clasped. If necessary, use a corner clincher to straighten bends. Spread compound on one side of the bead with the 5-inch (12.7cm) knife. Repeat on the opposite side.
Glide the knife straight down the corner and feather the compound with one stroke while holding the blade against the drywall and bead simultaneously—repeat on the opposite side. Allow for overnight drying of the compound. Glide the knife straight down the corner and feather the compound
8. Sand the Layer
It would help if you examined whether the compound is uniformly white, as this indicates that it is dry. (The wetter the area, the darker it appears.) Next, with a corner sanding block, sand the inside corners. You can use a pole sander and medium-grit abrasive to sand any other surfaces.
Remember to apply steady, moderate pressure. Sand only until rough areas are smoothed; do not sand down to the paper tape. Ensure you feel for rough spots and sand them if necessary.
9. Add More Layers
To add more layers, scoop up 2 inches (5.08 cm) of the compound with the 10-inch (25.4 cm) knife. Then, at each end of the blade, scrape off 2 inches (5.08 cm). Apply compound to all joints and screw heads in one pass, then smooth it out in another. Allow for overnight drying.
You should sand with fine-grit drywall sandpaper the next day and fill the whole edge of a 10-inch (25.4 cm) knife with compound for the third coat, then apply to joints and screw-heads as previously. Smooth to the point of being undetectable, with a feathery edge.
Finally, allow time for the compound to cure overnight before sanding again the next day. If you want to prime, simply wipe all surfaces with a moist cloth (source).
If you are finishing a concrete wall, drywall mud is a good compound to use. It will stick to concrete but will last longer in hot climates.