Shed / Barn / Pole Building Calculator

The shoelace (surveyor's) formula for the area of a simple polygon, wrapping the last vertex to the first; the perimeter is the Euclidean distance summed around that same closed list. Both are mathematical identities -- no trade convention and no published source stands behind either, and none is needed.

Omitted, and named as a material still to be counted, until the corner count is entered -- the wall lengths cannot imply it.

Ordered as king and jack studs, under the same material ids the header/opening screen uses, so a job that runs both screens reports the overlap instead of buying the pieces twice. Half the allowance is booked as kings and half as jacks, which is the split that screen's own model makes at its defaults; an allowance that does not halve evenly puts the odd piece on the kings.

Applied to every wall-run total (studs, plates, linear feet), mirroring shed-barn.ts's roofPlaneCount multiplier pattern.

Two connections per stud, one into each plate. Both rates are jobsite practice figures, NOT rows read from a fastening schedule -- an inspector's schedule outranks them. Excludes the bottom-plate fixing, which is nails to a subfloor or anchors to a slab depending on what this wall sits on.

Omitted, and named as a material still to be counted, until the rows are entered -- a wall's length says nothing about how many rows of blocking it carries. Measured as the full run per row; blocks cut to fit between studs come out slightly shorter.

Omitted, and named as a material still to be counted, until the run says how its ends are carried. A joist hung off a ledger or a beam face takes a hanger per hung end; one bearing on top of a plate takes none, and the run's dimensions are identical either way.

"span (ft) ~ lumber depth (in)" jobsite rule of thumb -- see shared/header-sizing.ts. Not code-based; verify before ordering.

L/360 for floors is IRC Table R301.7 ("floors and plastered ceilings"), applied to the live load alone -- the basis the published floor span tables are built on; the dead-plus-live L/240 companion check is IBC Table 1604.3's D+L column for floor members. L/240 for ceilings is IRC Table R301.7's "all other structural members" row. DEFLECTION ONLY: bending and shear are not checked, so this is not the code's allowable span. The modulus-of-elasticity values behind it are AWC's published No. 2 dimension-lumber design values and have NOT been verified against the NDS supplement itself -- see shared/joist-sizing.ts for the derivation.

Layout arithmetic, not a published figure: one rafter at every on-center position along the plane, plus one to close the last bay. Per single roof plane -- the whole-roof count is stated separately once the roof's plane count is entered, and is that figure times the count.

Shortens the theoretical rafter length by the ridge board's half-thickness, projected onto the slope, so the ordered board matches the actual birdsmouth/ridge cut.

Single roof plane, including the EAVE overhang. Plane length is the entered roof length — the building length along the eave — so a gable-end (rake) overhang is not included. Measured on the theoretical rafter length rather than the ridge-cut length: the ridge cut is where the board stops, and the covering runs over it to the ridge centerline.

Underside of the overhang only; zero when no overhang is entered.

Adapter multiplier, not a new formula -- the same one shed-barn.ts applies. Scales the roof area, eave length, soffit area and rafter count from this plane to every plane, and is what the project chain publishes. Withheld entirely until the plane count is entered: it is a property of the roof, so it is asked and never assumed. Valid for a mono-slope or a gable only, where every plane shares this one's length and slope; a hip's eave is the building perimeter rather than four roof lengths, so a hip is deliberately not expressible here.

Roof live load 20 PSF, L/delta=180, ceiling not attached to rafters. Not a snow-load table.

Cap shingles run the ridge and every hip off the same bundle, so they are one length. A hip roof's hips are often longer than its ridge, and the roof area cannot tell them apart -- a gable and a hip roof of equal area measure the same.

One end lap at each joint between 10 ft pieces. The piece count subtracts the lap on both sides because a lapped piece only advances the run by 10 ft minus the lap -- counting whole pieces comes out one short wherever the valley is an exact multiple of the stock length. The 6 in lap is a common manufacturer installation instruction, not an IRC dimension -- the code sends you to the manufacturer's instructions for valley lining. Check your product and change it here if it differs.

IRC R905.1.2. Required only where there is a history of ice forming along the eaves. Where it is required, each valley gets one 36 in course down its centreline -- that 3 ft is the membrane's own width, not a second assumption about how far up the valley it runs.

IRC R806.2. The 1/300 ratio applies only where BOTH exception conditions are met: 40 to 50 percent of the required ventilating area comes from ventilators in the upper portion of the attic, no more than 3 ft below the ridge measured vertically, with the balance at the eaves; and, in Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling. Otherwise the ratio is 1/150.

IRC R905.2.6 sets not less than four fasteners per strip shingle, or two per individual shingle, as the minimum; six is required in high-wind areas and wherever the manufacturer says so. R905.2.5 governs the nail itself (gauge, head, penetration), not how many.

Sized on the gross wall: the wrap is run over the openings and cut out afterwards.