Roofing & Gutters Diagrams
9 diagrams · 4 calculators
Roof pitch rise-over-run, footprint-vs-actual-area, shingle layer stacks, gable-area takeoffs, and gutter sizing, hangers and slope — turning a roof into an accurate, watertight material list.
Calculators in this category
Roofing & Gutters · 9 diagrams
- Roofing & Gutters
Roof pitch explained — rise over run, and how a 6:12 pitch becomes an angle and a slope multiplier
Roof pitch is rise over run: a 6:12 roof climbs 6″ for every 12″ of horizontal run. That single ratio fixes everything else — the rafter length (√(6²+12²)=13.42″ per foot of run), the angle (26.6°), the grade (50%), and the 1.118 slope multiplier used to size materials.
- Roofing & Gutters
Why a roof is bigger than the house footprint — footprint area times the pitch slope multiplier equals roof squares
Your roof is always bigger than your house footprint. Multiply the flat footprint area by the pitch slope multiplier (1.118 for a 6:12) to get true roof area, then divide by 100 to get roofing squares. A 1,500 sq ft footprint at 6:12 ≈ 1,677 sq ft ≈ 16.8 squares.
- Roofing & Gutters
What goes under shingles — the asphalt roof assembly from the deck to the ridge cap
What’s under the shingles, eave to ridge: roof deck, drip edge, an ice-and-water shield that must reach at least 24″ inside the warm wall line, underlayment lapped over it, a starter course, the overlapping field shingles, and the ridge cap. Each course covers the nails of the one below.
- Roofing & Gutters
Gutter size vs. capacity — how much roof a 5-inch vs 6-inch K-style drains
A gutter’s profile sets its capacity: a 5″ K-style drains ~4,500 sq ft of roof at 1 in/hr, a 6″ ~7,800 (≈1.7×). Size it by roof area ÷ your local rainfall intensity — big or steep roofs need 6″–7″ or more downspouts.
- Roofing & Gutters
Gutter slope and downspout layout — pitch to the downspouts, crown long runs
Gutters slope ~¼″ per 10 ft toward the downspouts (a long run crowns in the middle and falls both ways). Plan about one downspout per 30–40 ft — plus more wherever the roof area exceeds the gutter’s capacity.
- Roofing & Gutters
Gutter eave section — hidden hangers and drip edge lapped into the gutter
A gutter hangs on hidden hangers screwed into the fascia (~24″ o.c., tighter in snow/wind zones), and the drip edge must lap DOWN INTO the gutter — stop it short and water runs behind the gutter and rots the fascia.
- Roofing & Gutters
Gable area formula — ½ × width × peak height, with the peak height set by roof pitch
A gable is a triangle: area = ½ × width × peak height. The peak height comes from the pitch — (½ span) × pitch ÷ 12 — so a 30 ft wall at 6:12 is ½ × 30 × 7.5 = 112.5 ft².
- Roofing & Gutters
Standard symmetric gable vs. half/shed gable — why the same width and pitch give a different area
Same width, same pitch — the gable type changes everything. A symmetric gable’s pitch runs over ½ the span (72 ft², 2 rakes); a shed gable’s runs over the FULL span, so the peak is 2× taller and the area doubles (144 ft², 1 rake).
- Roofing & Gutters
Gable rake length and siding waste — the rake is the hypotenuse, and every course is cut at its angle
The rake (sloped edge) is the hypotenuse — √(run² + rise²) = 16.8 ft, not the 30 ft width — so size rake fascia and trim from it. And because every course is cut at the rake angle, gable siding wastes 12–15% (up to 25–30% on steep or narrow gables), more than a flat wall.