Q: Why are there so many different drywall compounds, and which ones are best for taping?
A: Myron Ferguson, a drywall and home-performance contractor from Middle Grove, N.Y., responds: The combination of tape and compound is what connects the drywall seams and inside corners together. So it goes without saying that you should use the products that create the strongest seams. But all the different compound choices can be mind boggling.
Drywall compounds fall into two general categories: setting compounds and drying compounds. Setting compounds come as powders that mix with water and harden through a chemical reaction. Drying compounds come premixed—in either a bucket or a box—and harden by air drying.
As a professional drywaller, I usually use setting compounds only when I need a product that will set quickly, such as when prepping a room (see “Prep Work Before Taping,” Aug/19). For most of my drywall work, I prefer drying compounds, especially for embedding paper or fiberglass-mat tape. Drying compounds are available in many varieties, including all-purpose compounds (in various weights) and specialized taping and topping compounds.
Taping compounds are formulated to have excellent bonding strength and crack resistance for embedding paper tape, although they work well with fiberglass-mat tape as well. Taping compounds are slick and easy to work with for embedding tape, but I would not recommend them for finish coats. They are difficult to smooth and feather, and they are tough to sand.
The next best product for embedding tape is standard all-purpose compound, which can also be used for finish coats. This is the compound you see most often at lumberyards and home centers. All-purpose heavyweight compound goes on slick and doesn’t dry out, which gives you a longer working time for embedding paper or mat tape. Although this compound can be used for finish coats, it doesn’t feather out and sand as easily, so I try to use it only for taping.
Lightweight all-purpose compound can be used for embedding tape, but it is not as strong as taping compound or heavyweight compound, so I try to use it only for fill and finish coats. Topping compounds formulated specifically for the finish coats are not nearly as strong as taping compounds, so I never use topping compound for embedding tape. Because topping compounds and lightweight all-purpose compounds are easier to smooth and feather, easier to sand, and shrink less, they make the best choices for the fill and finish coats.
I also recommend using the same lightweight or topping compound for both the fill coat and finish coat. The final finish coat or coats tend to be quite thin, and they are the coats that get sanded. When sanding the finish coat, you often sand through at high spots, ridges, or tool marks. If the fill and finish layers are the same material, they will sand the same, which results in a smoother finish. If you’ve used a harder compound for a lower layer, then the layers will not sand the same and the finish could have imperfections.
The “three bears” version of drywall compound is the midweight all-purpose compound. Midweight compound sands more easily than heavyweight compound and is better than lightweight compound for bedding tape. Many tapers use this product for the convenience of having just a single product on the jobsite.
If you’re looking for a specific type or weight, be aware that individual brand names for different compounds and formulations can be a bit misleading, and some products may not be available in certain parts of the country. Always read the label carefully to make sure the compound you’re buying will do the job you want it to do.
