Proper Use of Gypsum Board Fiberglass Joint Tape

Gypsum Board

• Gypsum board -- sometimes referred to as drywall or wallboard -- is used for the interior finishing of walls. It comes in 4-by-8-foot sheets and larger, in thicknesses from 1/4 inch to 5/8 inch. The core of drywall sheets consists of gypsum and other chemicals. Both sides are lined with paper to make for a smooth wall finish. Gypsum board is screwed or nailed to the interior walls, but something needs to be done about the gaps in between the installed sheets.

Finishing Wall Board

• The gaps between sheets of installed gypsum board have to be filled and finished for a smooth wall. Joint compound is applied where one sheet adjoins another. Joint compound can be purchased ready-mixed or in powder form that you must mix with water yourself. Joint compound by itself may shrink after it cures, causing cracks to form, so the joint needs to be strengthened with special tape.

Paper Tape

• Paper tape may be applied over the gypsum board joints after the first coat of joint compound is applied. After the paper is smoothed into place with a putty knife, final coats of compound may be applied over the tape. The tape keeps the joint from pulling apart and cracking after the compound dries and cures. Paper tape is not expensive, but it is a little more labor intensive to install. A simpler method is available.

Fiberglass Tape

• Fiberglass gypsum board tape is available for those who do not wish to use paper tape. Mesh fiberglass tape is sold is rolls and has a self-adhesive backing, which eliminates the first coat of joint compound used as a bedding for paper tape. Apply fiberglass tape directly to the gypsum board joints and press it into place with the handle of a utility knife to smooth out any wrinkles and to ensure the adhesive takes hold. Use the sharp end of the knife to cut the tape to length. Avoid overlapping the tape at intersecting joints, as double thickness may cause the tape to show through the final coat of compound. Apply high-strength joint compound over the mesh tape with a 6-or-8-inch-wide drywall knife. Use a 12-inch knife for the final finish coat of compound so that it can be tapered into the surrounding gypsum board. Once the final coat of compound has been sanded, your wall is ready to be painted.