There are plenty of different materials that can be used to finish off an exterior wall. Wood siding, vinyl, brick, stucco, and a myriad of other materials offer outstanding protection and weatherproofing. One of the materials that people don't normally think about is drywall. Mostly an interior wall type covering, drywall can be used on exterior walls if it's protected from any long exposure to moisture, or if it's used as a base for other kinds of siding.
If it's the outermost surface, drywall will need to be sealed to ensure that is lasts as long as possible. If you are looking to install drywall on an exterior wall, here are the steps to take.
Step 1 - Prepare Surface for Drywall
If you are placing the drywall over exposed studs, then you do not have to do any more work. However, if going over cement, block, stucco, or other flat wall covering, you will need to prepare the wall. Set up some 1x4 wood studs on the wall so that you will have something to attach the drywall to. Frame the wood studs the same as you would a normal stick built wall. Use construction adhesive to attach to the wall.
Step 2 - Install Vapor Barrier
On top of the wood studs, you will have to place some plastic to act as a vapor barrier between the exterior wall and the drywall. Tack one corner of the plastic to the bottom corner of the wall and spread it out along the frame. Staple it to the studs as you go along.
Step 3 - Attach Drywall To Studs
Start in the bottom corner and attach drywall to studs. Use 1/2 inch drywall screws to secure it to the studs. When you need to cut a piece, measure the section and then mark on the drywall with a chalkline. Set the drywall on some sawhorses and run your utility knife along the chalk line. Stand up the drywall and hit it in the back where you made the cut. The drywall should break cleanly at your cut. Continue installing drywall until the exterior wall is completed.
Step 4 - Apply Tape and Mud
Drywall will have many seams that need to be made smooth. Apply drywall mud to a section of seam and then run some drywall tape along the same seam. Use a trowel and press the tape into the mud. Apply another coat and smooth it out so there are not bumps or gaps. Continue until all seams are finished. With the screw holes, you only need to apply the mud. Make sure that it is flat and smooth.
Step 5 - Sand Down Drywall
If done correctly you should not have to sand all that much. Place a piece of sandpaper around a wood block and sand all the seam and screw holes. Wipe it down after to remove any dust.
Step 6 - Paint and Seal
Use a good quality exterior paint and give the drywall at least two coats. Once the paint dries, then apply two coats of sealer to protect the drywall from the weather.