Interior Finish: Drywall

Once the materials arrive onsite, verify that the correct items have been delivered, that all materials are in good condition, and that all materials are stored properly. Inspect the drywall for damage, including cracked or broken corners. Check for water damage and mold. Using cracked or water-damaged drywall ultimately causes cracking, ridging, and soft spots.

Always stock drywall on risers inside the home. Don't overload a floor's capacity to support the deadweight of the stacked sheets. A typical floor is designed to support 30 psf of dead load. On concrete floors, such as slab-on-grade or garage floors, place a plastic sheet under the risers to prevent moisture from being drawn up into the sheets while they're stacked.

Prior to installation, stand individual sheets on end. Position them around the room they'll be installed in. Taking this step will acclimatize the sheets to the room's temperature and humidity.

Maintain a small inventory of joint compound; manufacturers change the properties of joint compound depending on the season in order to control setting and drying times affected by the weather. Don't ever let the joint compound freeze. Freezing compromises the compound's chemical properties, affecting its ability to adhere to drywall, tape, and trim.

Store corner bead where it won't be damaged during construction. The best time to stock corner bead is after hanging the drywall when scrap material has been removed and the room has been swept clean.

Before the hanging crew begins, maintain the inside air temperature and framing surface temperature at a minimum of 50°F for at least 48 hours. This will precondition the framing to the ultimate indoor temperature and reduce the amount of moisture in the lumber (ideally, 19% or less). Preconditioning the framing prior to hanging can minimize drywall cracks by nearly 20%. Without preconditioning, edge cracks and nail pops can occur as soon as 24 hours after the heat or air conditioning is turned on. Also, drywall adhesive bonds better to lumber that's been conditioned. Ensure drywall and framing are also maintained at a minimum of 50°F for 48 hours prior to hanging.

Throughout hanging, finishing, and painting, keep the inside air temperature at a minimum of 55°F when crews are working and 50°F at all other times. Using joint compound at lower temperatures lengthens the drying time and reduces its ability to bond with the drywall surface. Cold temperatures also cause joint cracking and bond-to-tape failure.

The best way to control the temperature and maintain it consistently is to use the home's HVAC system. Have the furnace and air conditioning unit installed with a temporary thermostat during HVAC rough-in. During the electrical and plumbing rough-ins, have power and gas connected to the units. Leave the returns disconnected until after painting is finished to protect the HVAC system from dust and dirt during construction. Also, check the furnace filter periodically. Replace it as necessary, and definitely replace it prior to closing.

It's best to avoid using portable kerosene or propane space heaters, such as salamanders, to control temperature. These units add a significant amount of water vapor to the air, increasing the relative humidity inside the home and therefore increasing drying times for joint compound. Increased relative humidity can also damage the drywall. In addition, salamanders don't allow for consistent indoor temperature control—they heat the home unevenly. Freestanding units can also run out of fuel, allowing the indoor temperature to drop unexpectedly.

The relative humidity inside the home is impacted greatly by outdoor weather conditions. Although no one can control outdoor weather, it's possible to control the relative humidity inside the home. If you don't, the drywall will absorb the water vapor in the air, which will soften the gypsum core and expand the paper face. This can lead to sagging drywall, especially in ceilings. High humidity prohibits joint compound from drying thoroughly, leading to delayed shrinkage and bond failure. It also increases the chances for galvanized steel products to rust.

Eliminate moisture of any type, such as rain, snow, and standing water, from inside the home prior to hanging drywall, because moisture increases relative humidity. Drywall in direct contact with water will damage the paper face. To protect drywall from moisture, be sure the home is completely enclosed at least 48 hours prior to hanging.

Under the right conditions, ventilation can help exhaust some of the moisture in the air, which will help joint compound dry. To provide adequate ventilation during drying, open each window about ½", but only do so under optimum conditions.

Well before the drywall hanging crew ever walks onto a job site, the framing should be inspected for issues that may cause problems for the drywall. Many common drywall problems are actually caused by problems with the framing.

During the HVAC inspection, look for issues that will affect the quality of the drywall installation. Ensure that all mechanicals are installed as specified to avoid costly repairs and construction delays.

During the plumbing inspection, inspect for issues that will affect the quality of the drywall installation. Make sure all plumbing is installed correctly. For instance, verify that all drain hubs fit within the stud bays.

During the electrical inspection, make sure there are no issues that will affect the quality of the drywall installation. All electrical components should be installed as specified. For example, verify the position of all recessed lighting against the blueprints.

During the insulation inspection, look for issues that will affect the quality of the drywall installation. You want to identify and correct any issues with the insulation prior to hanging.

During hanging, drywall is first installed on the ceiling, followed by the walls. You want to ensure that the horizontal joints are tapered factory edges and the vertical joints are butt joints. At a wall opening, single sheets should be installed over the opening in a saddle configuration. When sheets "break" at a door or window opening, it's important that the joint doesn't fall on the jamb line. A joint at the jamb line will almost always crack. Fastening along the edges of the drywall sheets should meet the correct minimum distance of 3/8" from the edge of the sheet. You want to create a floating corner at wall-to-ceiling transitions by installing ceiling fasteners 12" from the edge and wall fasteners 8" down from the ceiling. Floating corners are forgiving of the natural expansion and contraction of framing, helping to minimize cracks in the drywall. Installing drywall clips at inside corners will create an equally effective version of a floating corner. To attach the top plate of the partition walls to the bottom truss chords, use truss clips. Truss clips keep roof trusses and partition walls connected without causing wall separation or drywall cracks at ceiling corners.

Adhesive provides 100% more tensile strength than fasteners alone and 50% more shear strength. Creating a stronger wall distributes the stresses in the wall better, reducing the potential for cracking and nail pops.

For best results, use a combination of adhesive and screws to attach drywall. The type of adhesive should be ASTM C557 standard drywall adhesive. Apply a 3/8" diameter round bead of adhesive to clean framing. When the drywall is pressed against the framing, the drywall will break the skin of the adhesive, ensuring a tight bond between the drywall and the framing. When applying adhesive, apply only enough adhesive to do two sheets at a time. Always follow the proper fastening schedule; ceilings and walls have different requirements.

Prior to installation, check the corner bead for any damage. Kinks and twists in the metal are nearly impossible to hide after the bead is installed. When you apply bead to a corner, make sure the angle of the corner bead doesn't exceed 90°; this ensures that the fasteners will be properly covered by joint compound. Fasteners should be spaced opposite one another every 6" to 8".

Using a paper-faced corner bead eliminates many of the issues caused by metal corner bead and fasteners. Paper-faced bead is installed with joint compound, which creates a continuous bond between the paper-faced bead and the drywall. The best results are achieved when the bead is installed using a hopper, which applies joint compound to the back surface of the bead. Use a corner bead roller to press the bead onto the wall, ensuring optimum adhesion.

Once hanging and corner bead installation are complete, inspect the work. This will give you a second look at the workmanship that's critical to end-product quality. Inspect all problem areas that you identified when the crew was beginning the job to be sure they're resolved satisfactorily. In addition, begin checking for new issues. Before the taping begins, mark these problems to be properly repaired now. Sloppy repair jobs or ignoring the problems will create other problems during taping, finishing, and beyond.

The specifications identify six levels of finishing, 0 through 5. The trade associations considered the following key factors when developing the finish level specifications:

• Location of the work to be done
• Type and angle of surface lighting (both natural and artificial)
• Orientation of the panels during installation
• Type of paint or wall covering to be used
• Method of application for paint and wall covering

The following table explains the most relevant levels of drywall finish, 1 through 5, including what each one looks like, when each is typically used in residential construction, and how each can be achieved.

Properly mixing joint compound is critical to quality. Excess water softens the drywall sheet, increases shrinkage, and causes sagging. Adding a small amount of water to the topcoat makes it smoother. Make sure the consistency of the joint compound is very creamy, reducing the amount of sanding later, which increases quality and job productivity.

At this stage, the crew applies a layer of joint compound at each drywall joint and embeds tape in the joint compound. Then, the crew smoothes out the tape with a thin layer of joint compound, removing any excess compound. They repeat these steps for each inside corner. The crew then covers each fastener head with joint compound, finishing up the process by covering the corner bead on each outside corner. The first coat application is critical because it establishes the strength of the joints. The goal is to create joints that are as strong as the sheets, minimizing cracking due to natural movement of the framing.

The second coat will help fill in all voids around the tape, corner bead, and fastener heads, making the drywall surface as smooth as possible for the third coat and ultimately for painting. With this in mind, inspect for proper application of the second coat around the taped joints, corner bead, and fasteners. Make sure all areas are covered and the joint compound is applied at the right thickness.

Once the second coat has been applied, it's critical to control the inside environment and drying time for the joint compound. Consistent temperature, good ventilation, and controlled humidity will help the joint compound dry quickly and evenly. Drastic temperature changes can cause the joint compound to dry unevenly and crack.

Under standard conditions, the drying time for the second coat should be 24 hours. Allowing at least this amount of drying time is essential for a high-quality drywall finish. After 24 hours, check the second coat to make sure it's completely dry before the third coat is applied.

At the third coat stage, the crew applies a very thin layer of joint compound over all previously mudded areas, to create a finish that's as smooth as possible. They feather the edges of the joint compound to seamlessly match the drywall surface. A watered-down standard weight joint compound or a lightweight joint compound is typically used to help achieve the desired smoothness.

If the final finish of drywall is to be textured, the crew typically applies this as a third coat. Texture can be created on walls, ceilings, or both, depending on homeowner preference and your company's standards. Popcorn finish, orange peel finish, and stipple finish are some of the common textures for walls and ceilings. Some factors that help to drive texture decisions include regional popularity and subcontractor familiarity with and skill at applying. Textured finishes do help to cover slight imperfections in drywall.

To achieve the textured finishes, the drywall crew uses joint compound that may have aggregates added or be thinned down, depending on the application method. Most textured finishes may be either spray-applied or hand-applied with a broad knife, brush, or roller, depending on the pattern desired. The crew coats all desired surfaces with one application. During drying or after drying is complete, the crew will run a broad knife over the textured areas to drag the surface, “knocking down” the severity of the texture and removing any sharp points. Timing for the drag and/or knockdown depends on the texture being created. For example, an orange peel finish is dragged or knocked down before drying, while a stipple finish is knocked down after drying is complete.

Sanding helps smooth out rough spots in the joint compound prior to painting. The sanding stage is one of the most important in achieving a high-quality drywall finish. Although not highly visible now, rough areas of joint compound over joints, fastener heads, and corner bead would be quite obvious if they were painted without being sanded. Paint, even flat paint, magnifies imperfections in drywall. To ensure a quality finish, it's critical to inspect the drywall after sanding and before the prime coat of paint is applied.