Have you ever looked in the dumpsters, marveling at the quantity of drywall that you paid for, shipped to your site, then pay again to haul it away and bury it? Your immediate assumption is that the drywall hangers were sloppy, and that could be the case. But perhaps it is really a design issue. See those 8-foot, 3-inch walls in the garage? See the 12-foot, 2-inch bedroom lengths? Or perhaps the purchasing manager got a great deal on 4x12-foot sheets. Good for him, not so good for the hangers. You’d better find the answer because uncovering anywhere from $250 to $1,200 in waste is typical in production units and even more in custom homes. There are two ratios that every builder should track for each model, yet no one does (note: for both ratios, leave out any amount purchased and installed in a garage):
A. Design efficiency: Square feet of drywall applied to walls and ceilings / square feet of living space. This ratio shows how carefully details are taken into consideration to get the greatest yield on material in the design stage. The ratio will usually be higher for smaller homes, although high ceilings, foyers, and cathedrals can throw that off. But when you find two models of similar size with substantially different ratios you’ll have an object lesson in the elimination of waste through Lean design. Study it thoroughly. No more 9-foot, 3-inch walls or 12-foot, 2-inch bedrooms.
B. Material yield: Square feet applied to walls and ceilings / square feet of drywall purchased. For clarity, express this one as a percentage. The ideal of course is 100 percent, and although that may be impossible, every point you fall below that is a quantitative measure of waste. If your ratio is 0.85, then 15 percent of what you purchased is waste, and for those who pay for labor by the sheet (a very bad idea) you also squandered 15 percent of the labor cost. Remember though, this is not all on the heads of your installation crews. If you don’t take the time and trouble to buy the board in the proper sizes, their ability to control waste is compromised. Measuring and tracking these ratios over time is not difficult, and significant savings will accrue.