Drywall and its seaming agent, joint compound, have plenty of advantages for home building and remodeling, including design flexibility and cost. But cleanliness has never been a high point for either material.
Drywall dust is as fine as talcum powder and it loves to travel. If there is even a tiny hole in the dust barrier, it is a sure thing that the drywall dust will find it and escape. Once released, drywall dust, borne by HVAC cycles and by air currents, can even end up at the other end of the house on your bedroom dresser. Drywall dust is so harmful that manufacturers of home vacuums often indicate that warranties are rendered invalid if the machines are used on drywall dust.
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How Low-Dust Joint Compound Works
The idea behind dust control joint compound is that it applies like regular joint compound, but its modified formula makes the dust heavier and cause it to clump as you sand. The clumps are heavy enough to drop to the floor rather than float into the air like regular powdery drywall sanding dust.
Regular joint compound contains over 35-percent limestone and less than 5-percent content each for attapulgite (an ingredient found in antidiarrheal medications), mica, and talc. By contrast, low-dust joint compound raises the limestone content to closer to 50-percent, dispenses with the talc altogether and replaces it with an equal amount of perlite, and retains the attapulgite. Drywall dust is sometimes described as having a talc-like consistency. This description is spot-on since talc is exactly the material that floats throughout your house. Removing the talc solves this problem.
The dust clumps are similar to coarse sawdust. If you have ever cut a piece of wood with a jigsaw, you have some idea of the aftermath of sanding a wall with dust control joint compound. The bulk of the dust piles up at the base of the wall. Then, there is a layer of fine dust radiating out another couple of feet. Outside of that is a very fine layer of dust extending to about 10 feet from the wall, with very little dust beyond 10 feet. Compared to the dust from regular joint compound, this is a noteworthy difference.
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Quality of Finish
One advantage of standard drywall joint compound is its smooth finish. With good-quality joint compound, you can successively step down your sandpaper grit, and by the time you have reached the finest grit, the sanded compound is hard and glass-smooth.
With low-dust joint compound, the best finish is one that is medium-hard and somewhat rougher, a degree short of glass-smooth. So, you will not want to use a low-dust joint compound for the final skim coat of a level 5 drywall finish.
Due to the clumping effect that prevents the material from breaking up readily into fine particles, dust control compound is slightly more difficult to sand than standard joint compound.
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Tips for Using Low-Dust Drywall Joint Compound
Using the low-dust joint compound does not mean you can sand drywall with abandon and leave the work area open to the rest of the house. You will still need to erect dust barriers if you want to keep the room or surrounding area dust-free. If you do use a barrier, dust control joint compound will be far less prone to escaping through small holes and seams in the barrier and traveling from one end of the house to the other.
Low-dust joint compound tends to cost two to three times more than conventional joint compound. Due to its higher cost, this type of joint compound may not be cost-effective for large areas. Instead, you may wish to confine your use of the dust-control joint compound to smaller areas that are in or near dust-sensitive areas.
Another problem with conventional drywall compound's dust occurs when you try to sweep it up. Every sweep of the broom seems to send more dust airborne than is deposited in the dustpan. This is why it is best to suck up the dust with a shop vacuum fitted with a drywall dust-compliant bag. But with low-dust joint compound, it is possible to sweep up the majority of the pile without creating too much of a dust cloud.