Question 1

How many roofing squares for a 1,200 sq ft house?

Accepted Answer

A 1,200 ft² footprint with 6/12 pitch needs about 14 squares of shingles including waste.

Question 2

How many bundles of shingles per square?

Accepted Answer

Three bundles per square is standard for architectural shingles. Heavy designer shingles may need four.

Question 3

How long do asphalt shingles last?

Accepted Answer

Three-tab: 15–20 years. Architectural: 25–30 years. Premium: 40+ years. Climate matters significantly.

Question 4

Why do I need the pitch factor to order shingles?

Accepted Answer

Because a roof surface is larger than the footprint under it. A 6/12 pitch multiplies plan area by 1.118, so a 1,500 ft² footprint is about 1,677 ft² of roof. Ordering off the footprint alone leaves you a square and a half short.

Question 5

How much underlayment do I need?

Accepted Answer

One roll of standard 15-lb felt covers about 400 ft², and synthetic underlayment typically 1,000 ft² per roll. Add ice-and-water shield along eaves and in valleys, which most cold-climate codes require separately.

Question 6

Can I install new shingles over old ones?

Accepted Answer

The IRC permits up to two layers on most roofs, but it is rarely a good idea: you cannot inspect the deck, the new shingles telegraph the old profile, the assembly runs hotter and fails sooner, and the added weight matters on marginal framing.

Question 7

How many nails per shingle?

Accepted Answer

Four in standard conditions and six in high-wind zones or on steep pitches, placed in the manufacturer nailing zone. Nailing above the strip voids most wind warranties and is the most common installation defect found after storm damage.

Question 8

What is the minimum roof pitch for shingles?

Accepted Answer

Two-in-twelve under IRC R905.2.2, and between 2/12 and 4/12 you must use a doubled underlayment. Below 2/12, shingles are not an acceptable covering — that roof needs a membrane system.

Question 9

How much does a new roof cost?

Accepted Answer

Architectural shingles run roughly $100–150 per square in material. Installed, most US markets land between $4.50 and $8 per square foot, with steep or complex roofs, tear-off of multiple layers, and deck repairs pushing it higher.

Roofing Calculator

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