When sheetrock (drywall is the gypsum board product and Sheetrock is a brand name, but the two words have come to be interchangeable) is hung, or installed, the joints are exposed and the nail or screws dimple the paper face of the sheetrock. Then begins the taping and floating process. To start with, drywall tape is applied to the joints and all the inside corners.
There are two types of drywall tape, the original paper type, and the newer fiberglass or plastic mesh type. The newer mesh type is preferred because of its superior holding power (the mud penetrates the mesh) and because of the fact that it has an adhesive on one side so it is easier to apply.
At this point, corner bead is applied to all the external corners. Again, there are two types. The first is the original metal corner bead and this is secured in place with a rubber mallet and a crimping tool. The newer type is plastic and is secured with staples. The advantage of the plastic corner bead is that it is rust proof.
Taping and Floating
The first stage is applying sheetrock compound, also known as mud, to the taped areas, the corner bead, and the nail and screw dimples.
The mud is applied with a taping knife. After this has dried, some minor sanding might be required. The surface should be free from lumps and ridges for floating, the next step.
Next the previously mudded areas are floated, that is, more mud is applied with a wider floating knife. The purpose of this step is to get the smoothest surface possible so that when the sheetrock is textured and/or painted, the joints and dimples will not be visible. To see how close we are to that goal we need to sand the floated areas.
Sanding the Sheetrock Joints
Always wear a dust mask when sanding drywall compound. A baseball cap is also recommended to help keep the drywall compound dust out of your eyes. The dust is very fine and lightweight and will hang in the air and slowly drift down so the chance of inhaling it is very real.
Sanding is done using a sanding pole attached to a sanding pad which swivels in all different directions. In order to sand, sandpaper or a sanding screen is attached to the pad. The screen is a more recent development and is superior because it will not clog up as quickly and lasts longer than the paper.
The proper technique is to sand evenly and smoothly and feather the compound on the edges where it reaches the paper. Remember, the goal is the smoothest surface possible.
Be careful not to sand the paper facing on the sheetrock because it will peel up and that area will have to be re-floated. Sanding sheetrock joints, and taping and floating, is something of and acquired skill, almost an art form.
How Smooth is the Sheetrock?
When you’re done sanding it’s time to check for a smooth surface. Do not expect perfection at this point. Do a visual inspection and draw a pencil mark on spots that need re-floating and re-sanding. Next go back and do it.
If you plan to use a high gloss paint you will have to be more particular. The higher the gloss, the more evident any imperfections will be, especially if the texture is to be minimal.