Check a roofing bid against your own count
Put your count next to the bid and go down it line by line. Each of these is a fair question to ask the roofer.
- Squares. Hold your squares of roof against the squares the roofer measured, and your squares to order against what they plan to buy. If the bid shows one number, ask which one it is. If it's far from yours, ask how they measured: the overhangs, a second pitch, dormers.
- Starter and caps. With architectural shingles, hip and ridge caps and the starter strip at the eaves come in their own bundles. See whether the bid lists them.
- Tear-off. Under the International Residential Code (the model building code), a roof replacement removes the old roofing down to the deck. A new layer can't go over a roof that already has two or more layers, or one that's water-soaked or deteriorated. Ask whether the bid tears the old roofing off or goes over it, and how many layers are on the roof now.
- Low slope. Asphalt shingles need a pitch of at least 2/12, and from 2/12 up to 4/12 the code calls for a double layer of underlayment, the water-resistant sheet under the shingles. On a low roof, look for it in the bid.
- Permit. Reroofing isn't on the model code's list of jobs that need no permit. Ask who applies for it, and check with your local building department.
- Shingle line. Ask which shingle the bid names. If it's a designer line, a bundle count well above yours can be right.
How many square feet of roof is on a 1,500 sq ft house?
Start from the footprint, not the living area. A one-story house with 1,500 sq ft of floor has about 1,500 sq ft of footprint. At a 6/12 pitch that's about 1,677 sq ft of roof. A two-story house with 1,500 sq ft of living area might sit on 750 sq ft, which is about 839 sq ft of roof at 6/12. Both figures leave out the overhangs, which add more.
A sloped roof covers more than the ground under it
The steeper the roof, the more it adds over the footprint: 1.4% at 2/12, 11.8% at 6/12 and 41.4% at 12/12. On a roof with two pitches, run each part through the calculator and add them. If the footprint is several rectangles, the square footage calculator, one of our free tools, adds them up.
How much bigger the roof is than its footprint, by pitch
How many bundles of shingles for a 2,000 sq ft roof?
Count 2,000 sq ft of roof surface, not a 2,000 sq ft house. That's 20 squares. Most 3-tab and architectural shingles come 3 bundles to a square, so 20 squares is 60 bundles before any extra. With 10% extra it's 66 bundles, and with 15% it's 69.
Check the wrapper before you trust the 3. GAF's Woodland line takes 4 bundles a square, and some designer shingles take 5. Owens Corning's Duration comes 3 bundles to a square, but those 3 bundles cover 98.4 sq ft, not 100.
How much extra to add for waste
Owens Corning and GAF both tell buyers to add 10% to 15% for trim and waste, and more on a complicated roof. The calculator's 10% for a simple gable and 15% for a hip or complex roof are our defaults inside that range, not the makers'. If your roofer works to another figure, type it in.
Before you collect bids
Your count tells you how big the roof is, not what it should cost. The free readiness assessment names the open decisions in your project and gives you a preliminary estimate before you ask contractors to bid. With Project Pilot Complete, the Bid Room lines up each contractor's proposal against one shared scope, so what a bid leaves out shows next to its total.