Eliminate Drywall Shadow Lines on Walls

Dear James: I am remodeling two rooms. I hung and finished drywall in one room, but there are shadow lines at many joints. Do you have any joint finishing tips to create flat, hidden joints? — Steve K.

Dear Steve: The drywall joint problem you are experiencing is actually called shadowing by professional drywall installers. It is typically more apparent at night under artificial light from table lamps located near a wall. This is why it is not noticeable all the time.

There are two common causes of shadowing. The first is applying too much drywall compound over the tape on the joint. This leaves a slight hump along the vertical drywall joint. When a lamp is switched on near the wall, this hump causes a slight shadow behind it. During the daytime, with ample light bouncing all around the room, the shadow is not as noticeable.

The other common cause is a different surface texture over the drywall joint. People normally sand the joint very carefully and it gets smoother than the rest of the wall. When it is painted with regular wall paint, this very smooth surface reflects light differently than the rest of the wall.

Place a long straight edge across the drywall joint to make sure it is not too high. If it is too high, sand it flat. If you have to sand all the way down into the drywall tape, you might as well strip off the tape and start over again.

When the joint is finished and flat, paint the entire wall with drywall sealer or primer. It is inexpensive and it seals the new drywall compound so it will absorb the wall paint at the same rate as the rest of the wall. The entire wall will also have the same texture to start with so it will look consistent when the wall paint is rolled on.

Nailing the drywall up to the wall studs is a job anyone can do well. The quality of the finished job depends on how well you finish the joints between the pieces of drywall. If too much drywall compound is used, it will result in the shadowing problem. If too little compound is used, the tape will come loose in several years and you will have to do the job again.

As a rule of thumb, three coats of drywall compound are required for a good-looking, lasting drywall joint. Drywall compound sands easily, so don’t try to smooth out each coat too much when applying it. If you do, you most likely will have it too thin.

One hint that can really help is to clean off the sides of the drywall compound bucket often, otherwise small specks of hard dry compound can get on your trowel. You will go crazy trying to spread it smoothly and evenly for the final coat. Also don’t be afraid to spread the compound out wide on either side of the joint.

If you are planning to add wallpaper over the drywall, it is still a good idea to finish the joints properly and seal and prime the wall. Within a few years, you may want to remove the wallpaper and paint the walls. Wallpaper adhesive is much easier to remove from a primed wall.

Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.