Drywall Cutting Tools and Tips
DEAR TIM: I'm a remodeling novice, and am going to be doing some drywall work soon. I've never worked with the material and have no idea how to cut it. Not only do I have to cut new sheets to size, but I also have to make cutouts in existing drywall walls and ceilings. A friend suggested I use a circular saw. That makes sense to me. What tools and techniques do you use to cut drywall? I'm interested in both accuracy, speed and safety. Rachel C., Tacoma, WA
DEAR RACHEL: I clearly remember one weekend driving to a potential customer's house to look at a job. His next door neighbor had a sheet of drywall laying flat on two sawhorses out on his driveway. He was attacking the drywall with a circular saw creating so much dust that I thought the EPA was going to issue a county-wide air quality alert. Suffice it to say I offered this man the some of the same advice I'll offer to you.
First, don't use a circular saw to cut drywall. It's like using a rock to hammer nails. Both are the wrong tools for the job. A circular saw creates giant clouds of unnecessary dust. This dust causes premature wear on the moving parts of the saw, as well as your lungs and those standing nearby.
Professional drywall hangers use a regular razor knife to make straight cuts on drywall. Standard drywall, or sheetrock, is simply a sandwich product. It's comprised of two outer layers of special paper that conceal a gypsum-based core. Each drywall manufacturer might have a special recipe of ingredients found in the core, including a high-purity synthetic gypsum that's recovered from the flue gasses that are emitted from coal-fired power plants.
Spinning saw blades work well with wood because they normally create a harmless dust for the most part. But the fine dust created by a spinning saw blade cutting through gypsum is not healthy for you or your power tools.
To cut a straight line with drywall and create minimal airborne dust, you just score one side of the drywall with a sharp razor knife. Apply enough pressure to completely cut through the paper and into the gypsum core about one eighth inch. You need to cut this line all the way across the piece of drywall from edge to edge.
After making the cut, you go to the other side of the drywall and apply pressure directly behind the cut line. This pressure causes the drywall panel to snap along the cut line and bend over completely on itself. You finish the cut by simply cutting through the paper backing on the other side of the drywall panel.
Standard drywall is one-half-inch thick. You can use this method to cut off pieces as narrow as one and one-half inches wide. If you need to cut narrower pieces from a sheet of drywall, it requires you to make deeper cuts with the razor knife into the gypsum core. Do this carefully so the razor knife cuts only the drywall and not you.
To make cuts into existing drywall that's screwed or nailed to walls or ceilings, you can make repeated cuts with a very sharp razor knife, but it's very time consuming and hard to do. The gypsum core creates a large amount of friction making the cutting difficult.
You can use a hand-powered saw that's especially made to cut through drywall. The blades are tapered and have a sharp tip that allows you to push it through the drywall with relative ease. The biggest problem is these blades are normally about 5 or 6 inches long and they can easily reach wires, cables, pipes and other things hidden behind the drywall. A rookie like you can easily create big and expensive repair problems in a hurry using one of these tools.
A new short metal blade has been developed for electric-powered reciprocating saws that's designed specifically to cut holes into existing drywall. The blade has a blunt tip, and it's only about one and one-quarter inch long. It doesn't have sharp teeth, but rather square notched cut outs. It does a splendid job of cutting drywall, but won't cut deep enough to harm anything behind the drywall, especially if you hold the blade at a 45-degree angle as you glide it across the surface of the drywall.
Be careful when cutting holes in drywall ceilings. Always wear safety goggles, not safety glasses. Drywall dust and small chunks of gypsum core in your eyes can cause you to make an expensive trip to an emergency room or eye doctor.
Professional drywall hangers use a small rotary cutting tool fitted with a bit that looks like a standard drill bit. This bit has special cutting edges on the spiral shaft that allow it to cut rapidly through drywall. These tools are used by every professional drywall hanger that I know. While they increase production by a factor of five or more, they also create small clouds of dust.
Author's Note: Rob Crangle sent the following email regarding fly ash in drywall.
Enjoy reading your articles. Just finished your article on drywall cutting techniques.
Your concerns regarding fly ash are quite valid. I'm the Gypsum Commodity Analyst at the US Geological Survey. About half of the country's drywall is made of synthetic gypsum, most of which comes from coal-fired electrical power plants, where, indeed, a lot of fly ash is also produced. Thankfully, almost none of that (I'd say zero, but there's likely a lab technician out there who would find a trace of it and make me a liar) ends up in the synthetic-gypsum production stream.
Agree that it's not a good idea to inhale large quantities of drywall dust, but that dust, even if the gypsum originated from a coal-fired plant, probably contains little to no fly ash.