Q. I recently read that wide shingles get two nails in the center as well as nails on the edges. Others say one nail in the center. Who’s right?

A. Chris Yerkes, a cedar-shingle installer certified by the Cedar Shake and Shingle Bureau (CSSB), and owner of Cedarworks, in Brewster, Mass., responds: The answer depends on whose guidelines you follow. If you go to the websites of both the CSSB (which has jurisdiction over red-cedar installation) and Maibec (which has white-cedar jurisdiction), you’ll find they offer slightly different guidelines for installing wide shingles.

The official guidelines from the CSSB regarding red-cedar shingles are as follows: Cedar shingles up to 10 inches (254mm) wide require two corrosion-resistant nails driven 3/4 inch (19mm) from each edge and 1 inch (25mm) above the exposure line. For shingles wider than 10 inches (254mm), drive two additional nails approximately 1 inch (25mm) apart near the center. To decrease the chance of splitting the shake or shingle, fasteners should be blunted. Siding nails should be ring- or twist-shank to improve holding. A ring-shank nail will have adequate holding power if it penetrates 3/4 inch (19mm) into the wood. Corrosion-resistant nails are needed to avoid iron stains caused by extractives in the wood and corrosion by acid rain, salt air, and the like.

On the other hand, Maibec’s installation guidelines for white-cedar shingles require that two fasteners per shingle, regardless of its width, be located 3/4 inch from each edge and 1 inch above the butt line of the overlapping shingle. Fasteners must penetrate solid nailable substrate (for example, plywood) a minimum of 1/2 inch.

As you can see, the nailing strategy for wide shingles differs depending on who you ask and what material you’re using. Both strategies above are ways of dealing with the same simple fact about cedar shingles, regardless of the species: Wide cedar shingles are likely to bow and crack over time. As shingles absorb moisture and give it up during normal seasonal cycles, the wood tends to expand. The wider the shingle, the greater the expansion. If a wide shingle has been nailed just along the edges, the center will bow out, creating unsightly ripples in the siding.

With repeated seasonal movement, a wide shingle will eventually crack, which can compromise the integrity of the siding. If a wide shingle is attached in the middle, the bowing might seem less pronounced, but the chances of cracking or splitting over time are the same. As contractors, we can’t afford to have a dissatisfied client demanding that we rip out and replace shingles that have bowed or cracked. In addition, blending in a repair might be next to impossible, especially if the shingles are prestained.

Our strategy is simple: We avoid using any shingle that is wider than about 8 inches on the wall, period. Instead, we cull any shingles wider than that as we come across them, and set them aside to be cut for the angled shingles on dormer cheeks or along gable edges. I’ve had some folks suggest that I just rip wide shingles into narrower widths. But ripping wide shingles is not worth the time and effort, especially with color-stained shingles because of having to go back and paint the cut edge to meet the warranty requirement. In the last few years, Maibec has started including a separate box of “wides” with each color-stain shingle order, specifically for installation along cheeks and gables. This relatively new idea seems to work and saves us the time of having to cull wide shingles from the regular stock.