Should you build to the dimensions of standard building materials?

Look at the ENERGY STAR recommendations for advanced framing. Check out USGBC's LEED for Homes guidelines. Look up the southface.org Earthcraft House points system. Look at David Marstens Green Remodeling book. They are all saying build the exterior of your house to 2 or 4 dimensions because those are the dimensions lumber comes in and that will reduce wood waste. There may be more to it though?

First, examine the math... So your wall is 12 long on the outside (no one says outside of what, let's assume framing). Framing at 24 on the center you use 7 studs and three 12 plates. No waste. That makes good sense.

But what about your structural sheathing (OSB)? That makes three sheets wide, but how tall is our wall? How tall is our floor cavity? How tall are the energy heels on our trusses? Let's assume 12 tall floors, 92-5/8 studs, and 12 energy heels on our trusses. That means we need an extra 1/4 sheet of OSB for every 4 sections of the wall to fill out for siding and hold in insulation. That's still not bad for waste.

But suppose we use a 2 exterior rigid insulation board over the OSB for extra insulation. To connect the corners correctly our walls get longer by the thickness of the foam sheets, creating cuts and waste. Or how about our sheetrock? The inside wall dimension is 12' minus the thickness of both walls, once again leaving cuts and waste. Or how about the siding? Framing thickness plus OSB plus foam equals 12' 2½" yet fiber cement siding comes in 12 lengths. More waste. And we have not yet figured out interior trim, exterior trim, cabinets, floor covering, service pathways, etc.

Bottom line, I say if you restrict your designs to 2 or 4 increments your design probably sucks. Design for the needs of the space. If a wall needs to be 11 to work well, let it be 11. If it needs to be 17' 5⅛".... you get the point. Let designers and architects work for the function and usability of space. Trust the craftspeople in the field to use the resources wisely.

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