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Roofing Materials Measurements - how much to buy?

I am planning on building a storage shed, and know everything that I need to purchase, with the exception of how much roofing materials. I am going to use 30 lb felt and 3 tab shingles, and the roof will be 170 square feet. How do I calculate the # of rolls of felt and the # of bundles of shingles that I should purchase?

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Posted 2011-02-01T16:54:11+0000  by trixie trixie

Hey trixie, welcome to the Home Depot Community!


Standard 3 tab shingles (25 year warranty or less) cover 100 square feet with 3 bundles.  Pricier (usually 30 year shingles are heavier, and you need 4 bundles to cover 100 square feet.  I will assume that you are getting the standard shingles.


To cover the bulk of the roof:  170 sq ft / 33.3 sq ft / bundle = 5.1 bundles.


For the eaves you need one reversed layer from end to end, as well as along the rakes from ridge to the eaves.  I will make up sizes so you can see how to do it and adapt your measurements:

Assume each half of the gable roof is 10 ft long (eave) by 8.5 ft high (rafter length or rake)

You have 1 eave and 2 rakes for each set of rafters.

So (8.5 x 2) + 10 = 27;  2 sets of rafters (27 x 2) = 54 feet.

Each shingle is about 3 feet long, and there are 21 shingles per bundle, or 63 linear feet/bundle.

So 54 ft  / 63 ft / bundle = 0.86 bundles.


Last is the ridge: You will need about 24 ridge caps for every 10 feet.

There are 3 caps (tabs) on each shingle, so 24 caps / 3 caps / shingle  = 8 shingles or (8 / 21) = 0.4 bundles.


OK.  Add them up (5.1 + 0.86 + 0.4) and get 6.36 bundles.


On a big job add 5% waste, 10% on a small one: 6.36 x 110% = 7 bundles.


Now that I’ve gone through that, buy 8 bundles and return the extra one if you don’t use it. :smileyhappy:


One roll of 30# felt covers 216 square feet.  You should be good with just one.

I hope this helps,



Posted 2011-02-01T18:16:11+0000  by Chris_HD_CHI
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