How to Blend Old Drywall With New Drywall
Often, a DIYer must blend old drywall with existing drywall to repair a hole or damage created during another project. Common projects that often lead to a drywall repair are plumbing and electrical repairs or water damage repairs resulting from burst/leaking pipes or compromised roofs. While it may be difficult for a novice DIY enthusiast to produce a seamless drywall patch, the chances of success increase when you institute the same techniques used by professional drywall and home repair contractors.
Step 1 - Remove the Damage
Remove the damaged section of drywall between two existing wall studs. A stud finder is ideal to locate the centers of existing wall studs. Use a utility knife and straight edge or level to score a plumb line on the drywall to be removed so that the cuts fall on the centers of each wall stud. This will provide a solid nailing surface for the side edges of the new drywall.
Step 2 - Remove Hardware
Prepare the wall studs by removing any exposed drywall nails or screws using a hammer or screw gun.
Step 3 - Remove the Outer Paper
Lightly score the existing drywall edges with the utility knife approximately 1 1/2 inches around the opening and remove the thin, outer layer of paper. Removing the paper will provide a small groove that will help to absorb or compensate for the thickness of the mesh tape.
Step 4 - Install the New Piece
Install a new piece of drywall in the wall opening. Secure the new material to the wall studs with drywall nails or screws using the hammer or screw gun.
Step 5 - Cover Seams With Mesh Tape
Cover all seams of the drywall repair with a strip of self-adhesive drywall mesh tape. If you plan to use paper joint tape, you will first need to apply a thin layer of joint compound to hold the paper tape in place.
Step 6 - Mix Joint Compound
Prepare your joint compound. Most home improvement centers sell premixed joint compound in small pails or five-gallon buckets. For the best results and easier application, spin or mix the mud with a power drill and mixing paddle before applying.
Step 7 - Cover Seams
Fill a drywall pan with prepared joint compound and apply a thin layer over the seams. Be careful to not apply too much pressure as this could displace the joint tape. This is definitely the tricky part, as you must apply a thin and even coat to achieve a professional result. Too much or too thick, and your repair will require additional sanding. The goal is to achieve a flat and smooth repair.
Step 8 - Allow the Compound to Dry
Allow the joint compound to dry. Times will vary depending on the weather and the type of compound you use. Fast setting joint compounds are available at most home improvement centers with drying times between five and 45 minutes.
After drying is complete, sand the repaired area with an 80 to 120-grit sanding block to remove any ripples and to smooth the surface. Repeat this process at least two more times.
It may be necessary to texture your drywall repair. Many products available at home improvement centers are designed to duplicate a wide variety of texture patterns. Most are sold in spray cans with an adjustable nozzle that allows you to match your existing texture.
Hold the drywall knife firmly at between 15 and 25 degrees while applying adequate, consistent pressure when spreading the joint compound to achieve the best results.
Practice spreading the joint compound on a scrap piece of drywall to get the feel of the drywall knife and material.
Do not be afraid to apply a final skim coat over the entire area and sand to improve the repair's appearance.
Speed up drying times between coats by directing a fan on the repaired area.
Wear a respirator mask when sanding drywall and wear protective eye gear when using power tools. Use caution when removing drywall to avoid damage to concealed electrical wires and plumbing.