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Corrugated Metal Roofing Calculator

Calculate corrugated metal sheets, screws, and overlap requirements. Features overlap visualizer logic and net coverage calculations for DIY and agricultural projects.

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About

Corrugated roofing is the backbone of agricultural and utility structures, but calculating requirements involves more than simple square footage. A critical factor is Net Coverage. A standard "26-inch" sheet does not cover 26 inches of roof; it loses width to the side lap (usually 1.5 or 2.5 corrugations) and length to the end lap (minimum 6 inches). Failing to account for this leads to material shortages halfway through the job.

This calculator determines the precise number of sheets by factoring in the overlap geometry. It also generates a fastener schedule. Unlike wood framing where "more is better," excessive screws in metal roofing restrict thermal movement, enlarging holes and causing leaks. We use industry-standard patterns (e.g., adjacent to ribs vs. valley fixing) to estimate the optimal screw count.

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Formulas

Total sheets depend on the rows (up the slope) and columns (across the eave). We first calculate Net Width (Wnet) and Net Length (Lnet):

Wnet = Wgross - Oside
Lnet = Lsheet - Oend

The total count (Ntotal) is the product of columns and rows:

Ntotal = ceilRoofWidthWnet × ceilRoofLengthLnet

Reference Data

Sheet TypeGross WidthOverlap (Side)Net CoverageEnd Lap (Rec)Screw Loc
2-1/2 inch Corrugated26 in2.5 in (1 lap)24 in6 inRidge
2-1/2 inch Corrugated26 in5.0 in (2 laps)21.5 in6 inRidge
7/8 inch Corrugated37 in5 in32 in8 inValley
R-Panel (PBR)38.25 in2.25 in36 in6 inValley
5V Crimp26 in2 in24 in6 inPeak
Box Rib34 in2 in32 in6 inValley
Ag Panel38 in2 in36 in6 inValley
Deep Rib (Industrial)42 in6 in36 in12 inValley

Frequently Asked Questions

For standard residential or shed roofs with a decent pitch (above 3:12), a 1-corrugation overlap is sufficient. For low-slope roofs (below 3:12) or areas with heavy driving rain, a 2-corrugation overlap is recommended to prevent water from siphoning through the lap.
If you are fastening into the "valley" (the flat part against the wood), screws should penetrate the wood by at least 1 inch (usually 1.5-inch screws). If you are fastening into the "ridge" (the top of the wave), you need the wave height plus 1 inch (often 2.5-inch screws). Ridge fastening is more watertight but prone to overtightening.
Closure strips are foam profiles that match the wave of your metal. They are inserted at the eave and ridge. You absolutely need them to keep out birds, bugs, and wind-driven rain. Without them, your roof is essentially open to the elements.
No, this tool focuses on the metal skin (sheets and screws). Purlin spacing depends on your local snow load and truss spacing, though 24 inches on center is a common standard for metal roofs.