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Question DetailsAsked on 1/26/2014

how do I figure out how many packages of asphalt shingles I need to buy for my 28x36 cape cod home

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5 Answers


First off it is not the size of the house you need to know it is the size of the roof as it is larger than the foot print of the house due to the slope of the roof. You can either measure the roof slope or the total rise of the roof and divide the overall width of the house including overhangs and do the math for the diagonal of a triangle and then the width of the house plus any overhangs at the eaves and multipy the two. The number you are looking for is the number of squares you need, 1 square = 100sf. All shingles that I know of are sold either 3 bundles to a square or for dimensionals 4 per square. Overly simplified but I hope you get the idea.


Answered 6 years ago by ContractorDon



Don nailed it.

You have to know the square footage and cut level of the roof to properly estimate.


Answered 6 years ago by WoWHomeSolutions


I would strongly suggest buying at least one full bundle extra - two if your count is close to a whole number of bundles. That leaves a part bundle (or the second one if computed area is close to round number of bundles) for mistakes, cuts (remember there is wastage in valley cuts), etc. - plus at least one whole bundle for spares for future repairs so you have matching color.

Don't forget to try to get all one color batch - not just color code, but actuall plant batch number. Each production run of a color has a separate batch number, and color can noticeably vary between batches.

Also - don't forget to count extras or special shingles (whichever way you are going) for ridge vent covering, ridge capping, valley overlap, and starter row shingles, and also for disposal of short cuts at gables - all these extra needs are usually taken care of by a flat percentage overbuy.

Here is a google search term you can use to find a number of sources on how to account for these various needs for different roof shapes - how many shingles to buy

Answered 6 years ago by LCD


So many variables...

For the most accuracy you really need to climb up on the roof and measure the width and length of each piece of roofing. Geometry comes into play here. Valleys produce triangles in the roof which means you need to calculate the area of the triangle. Depending on how many valleys you have you will need additional shingles for waste. Also, as others stated, don't forget the wate at the ends and your starters, unless you are using a starter roll. Then if you are using 3-tab shingles you need to add in the ridge caps. If dimensional, measure the length of the ridge for coordinating caps or do like most roofers and cut your own out of matching 3-tab shingles. Whatever your measurements of the surface area of the roof come out to you are generally safe with about 20% over for the waste, starters and caps if using 3-tab shingles. If you somehow wind up with too many bundles (always keep at least one, two is better) most retailers will allow you to return them if unopened. It is better to have too many on site out of a matching batch then have to return to the store for 1 or 2 bundles (or a square depending on where you buy them from) which probably won't match the first batch exactly.

Answered 6 years ago by Todd's Home Services


One thing I forgot to mention on the spare shingles to get for future repairs - you have to open up the edge of the pack and slip kitchen waxed paper in between the shingles at the tar strips, or they will stick to each other over time.

Answered 6 years ago by LCD

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