Roof batten calculator

The same pure function powers the free browser tool and the paid API, so a phone-side estimate matches a scripted purchase order later. Non-positive area, width, or spacing is rejected with invalid_input instead of a silent nonsense count.

How the rows and linear-feet formula works

With a fifty-foot slope and one-foot spacing you get fifty-one rows; with sixteen-inch centers (about one point three three three feet) the same slope yields thirty-eight rows after flooring the quotient and adding one. Waste percent must be zero or positive when supplied. Model one rectangular roof plane: battens run parallel to the eave, so each course is as long as roof_width, and courses step up the slope at a fixed center-to-center batten_spacing (the gauge printed on the tile or metal panel data sheet). Slope length along the rafter plane is roof_area divided by roof_width when area and width share one unit system—for example two thousand square feet with a forty-foot eave implies a fifty-foot slope length. Course count uses the inclusive-end rule taught on job sites and in estimating handbooks: place a batten at the eaves reference, then every spacing along the slope, including a course at or before the ridge when the last step still fits, which is exactly batten_rows equals floor of slope_length divided by batten_spacing plus one. Total net linear length is batten_rows times roof_width—the sum of every course. Optional waste_percent inflates that length to linear_feet_ordered so cuts, hip and valley damage, and damaged stock are covered without changing the geometric row count. The response also reports spacing_count (rows minus one), covered_slope (spacing_count times spacing), and ridge_gap (slope length minus covered_slope) so you can see whether the last gap is short of a full gauge and decide to tighten gauge or add a ridge course per manufacturer rules. The pipeline is deterministic floating-point arithmetic with no random seeds, no wall-clock timestamps, and no network calls, so identical inputs always produce identical JSON. Roof area, roof width, and batten spacing must each be strictly positive; zero or negative values are rejected with invalid_input because they are non-physical and would not define a purchase quantity.

What you send and what you get back

Classic check: two thousand square feet, forty-foot width, spacing one point three three three three three three feet (sixteen-inch centers), ten percent waste—slope length is fifty, rows are thirty-eight, linear feet is one thousand five hundred twenty, ordered length is one thousand six hundred seventy-two. Send three required finite numbers: roof_area for the surface you will batten in square units, roof_width for the eave width of the plane in linear units (each batten’s length), and batten_spacing for center-to-center gauge in the same linear unit. Optionally send waste_percent as a non-negative percent; when omitted it defaults to zero so linear_feet_ordered matches linear_feet. Missing fields, non-numeric strings, NaN, and Infinity fail with invalid_input and are not charged. When roof_area is zero or negative the request fails with a message that non-positive area is not allowed; the same positivity rule applies to roof_width and batten_spacing, and negative waste is rejected separately. On success the response echoes cleaned inputs including waste_percent, slope_length, integer batten_rows, spacing_count, covered_slope, ridge_gap, net linear_feet, linear_feet_ordered after waste, a unit_note reminding you to keep one unit system and restating the row formula, and a short formula string for documentation. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.

Where roof batten calculators show up in real work

Homeowners and owner-builders installing clay, concrete, or slate tiles need a trustworthy linear-feet and row count before ordering battens or booking delivery, especially when treated timber has long lead times. Metal-roof crews setting horizontal purlins or battens under standing-seam or exposed-fastener panels use the same geometry with the manufacturer’s on-center spacing converted into feet or metres. If you later need counter-batten verticals, hip and valley waste tables, underlayment rolls, tile counts, or metal panel counts, treat those as separate search intents and landings rather than overloading this roof batten linear-feet and rows calculator page. Roofing contractors build takeoffs from measured surface area and eave width; a single deterministic endpoint that applies floor-plus-one rows and an explicit waste percent reduces spreadsheet drift between the estimator and the purchasing clerk. Building-supply counters comparing two gauges for the same house can swap only batten_spacing while holding area and width fixed, then rank linear_feet and ordered length without re-deriving slope length each time. Property managers planning multi-building re-roofs feed a batch of areas and widths through the API and attach linear_feet_ordered to purchase orders so overstock stays intentional rather than accidental. Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.