Everything You Need to Know About Drywall
Have a question about drywall? Here is our ultimate guide to all things drywall, from joint compound to corner bead options.
Choosing the right drywall
To hang and finish drywall, you need drywall sheets, joint compound, tape, fasteners and edge treatments. That seems straightforward, but when youre standing in the drywall aisle at the home center, the choices arent so simple.
In this story, well walk you through the assortment of materials to help you make the right choices for your jobsite.
Is drywall fire-resistant?
Type X drywall is 5/8 in. thick and designed to slow the spread of fire. It is often required on garage walls and ceilings that adjoin living spaces, ceilings between living spaces inside the house, and under stairs.
Talk to your local building inspector to find out where and which kind of Type X is required. There are many varieties, each with a different fire rating. If you install the wrong type, an inspector can require you to tear it off and replace it.
Is drywall mold and moisture resistant?
Also called greenboard, mold-and-mildew-resistant 1/2-in. drywall is a somewhat different animal. Manufacturers use various methods to eliminate or treat the paper that covers the gypsum core. Getting rid of the organic paper food source was supposed to keep mold and mildew from growing. Builders used to install it in wet and damp locations, placing it behind tile in shower and bath enclosures. Those enclosures have already been or soon will be replaced as the greenboard fails.
Pro Tip: Although youll still find greenboard at home centers, we advise against using it, especially for tile backing in wet areas. There are much better alternatives for tile in wet locationscement board, for one.
1/2-in. drywall is the best choice for most walls and some ceilings. There are standard and lightweight versions. Lightweight is stronger and weighs 25 percent less.
Pro Tip: Spend a few extra bucks and get ultralight or lightweight drywall. It is easier to handle and stiffer, so it can cover ceilings that have joists spaced at 24 in. Thats why some stores no longer even carry standard 1/2-in. drywall.
3/8-in. and -in. drywall
If youre doing repairs in a house that was built in the 50s or 60s, you may very well have 3/8-in. drywall. Youll want to match that thickness to patch an existing wall. Measure the existing drywall or take off a switch plate cover to find out.
Pro Tip: Unless youre matching existing drywall, theres rarely a good reason to use 3/8-in. drywall. Remember that window and doorjambs are generally sized to be flush with 1/2-in. drywall.
1/4-in. drywall is a very thin material so it is mostly used to cover bad walls: cracked plaster or unremovable wallpaper, for example. Because it is more flexible, it is also sometimes used on arches or applied in two layers on curved walls. Specialty stores carry drywall thats super bendableflexible enough to drywall the inside of a barrel!
Pro Tip: Screws dont countersink well in 1/4-in. drywall, so construction adhesive is a better choice if youre covering bad surfaces. Tack it in place with a few nails until the adhesive sets.
Which drying compound is the best?
Drying compound comes premixed in buckets and boxes. As the name suggests, it hardens as the water in it evaporates. There are variations, but these are the two basic types (Next Slides):
All-purpose compound contains a lot of adhesive, making it the hardest, strongest type of drying compound. That strength makes it a good choice for the first coat (when you embed paper tape). You can use it for following coats too, but sanding will give you a workout.
The main advantage of lightweight mud is that it is easier to sand. The downside is that it is not as hard or strong, so it is a bit more likely to dent when bumped or to crack at joints. Look for the term lightweight on the label. Dont use lightweight compound to embed mesh joint tape; that combination sometimes leads to cracks.
Setting compound is a powder that you mix with water just before use. It hardens by chemical reaction rather than by drying. The working time is usually the number thats in the name. Besides hardening fast and allowing you to apply the next coat sooner, setting compound has three advantages over other joint compounds: It is harder, stronger, and shrinks much less. Setting compound is perfect for filling larger holes and bedding tape, but its much harder to sand, so it should be should never be used as a last coat.
Regular setting compound
This compound is very hard, very strongand almost impossible to sand.
When it comes to drywall there are three main types of tape. First is paper tape. Paper tape is cheap and, surprisingly, stronger than fiberglass tape. And unlike fiberglass tape, it is pre-creased in the middle so you can fold it to tape inside corners. However, it takes a bit more skill to embed it in drywall seams.
The second main type of tape is fiberglass mesh. Mesh is far easier to use than paper. It has adhesive on one side; you just stick it to the wall and mud over it. Mesh tape is super forgiving for first-time tapers. But youll still have to use paper tape or reinforced paper tape for corners at wall-to-wall and wall-to-ceiling joints. Since it is not as crack resistant as paper tape, setting compound (standard or lightweight) is usually recommended for embedding mesh tape.
Reinforced Paper Tape
The third and final tape type is reinforced paper tape. Designed for inside corners and wall-to-ceiling angles, reinforced paper tape has plastic or metal strips on the back. They dont make the joint stronger, but they do provide a stiff guide for your knife, making it easy to keep corners straight.
Choose drywall screws rather than nailsnails are far more likely to work loose and cause ugly craters or pops. The screw length depends on the drywall thickness: 1-5/8-in. screws are for 5/8-in. drywall; 1-1/4-in. screws are for anything thinner. Coarse threads are for wood studs; fine threads for steel studs.
Youll find drywall screws with thin (No. 6) and thick (No. 8) shanks. Choose the thin ones. Thick-shank screws are harder to drive, break out drywall near edges and leave shredded paper around the screw head.
Edge and Corner Beads
Whenever drywall meets another surface like stone, brick or paneling, you need a neat way to finish the edge. You can always use wood trim, but there are some other options.
You have many choices for outside corners: metal or vinyl, square or bullnose, even bead for non-90-degree corners or arches. The big difference is how theyre installed. Standard metal can be nailed on and then taped; vinyl corner bead should be applied with special adhesive and staples. Paper-faced versions get glued into place with joint compound.
Pro Tips: Choose metal corner bead instead of vinyl or paper-faced bead. Its easier to install and requires only ordinary tools. Exception: In damp areas like bathrooms and spas, vinyl is a good, rust-proof choice.
For our full story on all things corner bead, click here. Also, check out this video explaining the pros and cons of the four main corner bead types:
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