Red Cedar Shingle Coverage Calculator

A shingle calculator is an excellent way to figure out exactly how much wood you will need. Too few means waiting around for more orders or having to use two colors of shingles (which doesn’t look great). Too many means wasted space and money.

Focusing on exposure make this math realy easy and takes away the guesswork of how many bundles of cedar shingles you need per square. But there’s no need to do the math yourself: The calculator take care of converting square feet into total area covered.

How to Use a Shingle Calculator

The most important variable to feed in is weather exposure, which is the exposed part of shingle projecting beyond the next shingle down. This varies depending off both length of shingles and pitch (or slope) of roof. On steeper pitches where water runs off quickly, exposure can be greater; on flatter ones where it might back up, you must overlap them more tight. Five and a half inches is a typical exposure for an eighteen-inch-long No. 1 grade shingle on a high-pitched roof; on a wall, the same shingle may have an exposure of eight and a half inches or more. The reason? Walls is not under as much direct water pressure.

Always consider the edges, and the calculator asks you how long those are: How many corners? Hips? Starter runs? Those take more material per square foot different than does the flat part of roof. Although they’re not purely decorative trim, the starter row of shingles is a structural element, anchoring the bottom course and protecting it against wind uplift. Hip and ridge caps gets cut on an angle; for every foot of length, you end up with less actual cap then you would on primary field.

The more complicated your roof’s shape, valleys, dormers, the higher your waste factor ought to be. For a simple gable, twelve percent is plenty conservative; if there is lots of interlocking hips that look like a weaver’s work basket, you may want to go as high as 18 or even 20 percent. Better to have some extra bundles in the back of the pickup truck than waiting around for the delivery guy at the last minute one day midweek.

Blue Label No. 1 is the straightest, cleanest grade and you can space it tighter and more consistently. Other grades, like Red Label No. 2 or Black Label No. 3, has greater variation in width, knots, splits, etc., meaning you’ll have to sort them out a little harder. There’s also going to be a higher percentage of pieces you don’t think look good enough to use, resulting in higher waste. The calculator enables you to account for this by adjusting the bundle coverage to match. A theoretical square = 100 sq ft. In the real world, however, things never go as planned. Setting the bundle coverage a hair lower reflects this fact; you’re accounting for sorting up front.

And there’s another expense: Fasteners, which for cedar should of be either screws or nails that resist corrosion. The wrong ones will stain over time, or just fail later. The tool gives an estimate of how many fasteners it thinks you’ll need for the whole project (including all courses), so you don’t have to stop work halfway through a rafter because you ran out of nails. A little thing, but forgetting a bucket of screws stops work faster than running out of shingles.

Math isn’t realy the focus when estimating cedar shingles. It’s more about learning how the stuff behaves in nature (wood + water). The tool is a good starting place, but ultimately it’s all about knowing what makes your particular roof tick. Take its number as gospel, round up to the next full bundle, and mentally add the waste factor you selected. Getting that bit of insurance won’t make you a pessimist, it will prepare you for a stress-free project that leaves you with a rock-solid roof and no fear of being short.