Waterproofing, cladding, and siding takeoff

Cladding is measured over the outer face of the wall, so each elevation polygon runs outside corner to outside corner, the full exposed width. The stud centerline under-measures the face by one wall thickness at every corner, and the footprint or wall line below omits the true face and any overhang, so neither is the right boundary for a surface-area takeoff.

Vertically the polygon starts at the bottom of the lowest course and stops at the underside of the eave or soffit. The bottom is not grade itself but the required clearance line above grade, roof, or deck. Getting the boundary right is the most reusable move in the trade, because the field area follows directly from it.

On a gable end the wall rises into a triangle above the eave line, and the cladding covers it, so the elevation polygon must extend to the peak with its sloped sides following the underside of the rake. The triangle area is pure geometry, base times height divided by two.

Tracing only the rectangle below the eave silently drops the entire gable on every gable-end wall. This is the single most common under-measure on a siding takeoff, and it is fully deterministic once the base and height are read off the drawing.

Cladding is a discrete, cut and lapped product, so the universal rule is cover then deduct: trace the wall solid, then subtract each door and window to get the net area. This is the opposite of paint, which under the Painting Contractors Association Standard P10 leaves openings under 100 square feet in. One structural exception is a unitized curtain wall or panel system, which is measured gross of its own openings because the glass, panels, and doors are part of the same system, as carried over from SMM7 Section H.

Even under cover then deduct, a minimum void is left in because the cut-around scrap roughly offsets the saving. The size at which a deduction begins is the one genuinely region-specific number. Under RICS NRM2 no deduction is made for voids up to 1.00 square metre, about 10.76 square feet, and the legacy SMM7 threshold was 0.5 square metre. German VOB/C practice over-measures small facade openings, meaning it keeps them, up to roughly 2.5 square metres under the general and finishing trade conventions (for example DIN 18363 painting), while tile and stone work under DIN 18352 uses 0.1 square metre. US and Canadian practice has no codified figure: it deducts each whole window and door and lets waste absorb anything smaller than about one panel or sheet of coverage.

Cladding does not run to grade. Install specifications require a gap, and the measured bottom of the elevation polygon is that clearance line rather than grade itself. Fiber-cement, for example, calls for 6 inches to finished grade and 1 to 2 inches to roofs, decks, paths, and driveways.

Measuring to grade over-measures the field and mis-locates the starter course. The clearance figures are product specific, so vinyl and metal carry their own starter datums and the value should be set to match the system in use.

The unit splits the world. US and Canadian materials are ordered in squares, where one square equals 100 square feet, and quoted per square foot, while UK, Australia and New Zealand, and European measured bills use square metres. RICS NRM2 additionally requires narrow widths under about 600 millimetres, such as cladding strips and trims, to be measured lineally rather than as area.

Lap and board siding cover less than their full plank width because each course overlaps the one below, with a fiber-cement minimum head lap of 1 and 1 quarter inches. The lap is paid for through the exposure, which is the board width minus the lap, so adding a separate lap allowance on top double counts. The conversion to material is deterministic: lineal feet equals net square feet times 12 divided by the exposure in inches, with the course count taken as the wall height divided by the maximum exposure, rounded up, and the exposure then re-divided evenly so courses land cleanly. Getting the exposure wrong scales the entire material order.

The water-resistive barrier, or house wrap, runs continuous behind the cladding, so its area is the net wall area but it is not deducted for the same small openings, because it wraps into them. A code-fixed lap is then added. IRC R703.2 requires one layer of No. 15 asphalt felt to ASTM D226 Type I or an approved barrier, with the upper layer lapped over the lower by at least 2 inches and joints lapped by at least 6 inches, so the barrier area does not equal the finished cladding area.

Water-managed claddings also require a means of draining water that gets behind the veneer. IRC R703.1.1 gives two paths: a prescriptive minimum 3 sixteenths inch (4.8 millimetre) drainage space, or a space with at least 90 percent drainage efficiency tested to ASTM E2273 or Annex A2 of ASTM E2925. This decides whether a furring or rainscreen cavity, with its battens and clips, is in scope at all.

Flashing is a separately measured class. Code requires flashing at the head and sides of every exterior window and door, with pan flashing at the sill, plus kickout and step flashing where a sloped roof meets a sidewall and base or weep flashing at terminations. Under IRC R703.4 and R703.4.1, and the SMACNA Architectural Sheet Metal Manual, head, sill, and jamb flashing is taken in linear feet per opening, step and kickout flashing along roof-to-wall intersections, and base flashing along the bottom termination.

Outside and inside corners, starter strip, J-channel, trim, and drip cap are linear items, ordered and priced apart from the field area. Outside-corner length runs with the wall height at each corner, starter follows the bottom-course length, J-channel and trim wrap each opening perimeter, and drip cap runs along each opening head. Corner posts, corner boards, and terminations are additionally counted as each items off the corner schedule, so the order resolves to whole posts and boards at stock lengths. Folding accessories into the field area understates them and corrupts the unit basis.

Small penetrations such as vents, hose bibs, lights, and conduits sit well below any void threshold, so they are not area deductions: waste absorbs the cut-around. They are instead counted, because each generates a flashing, trim, or sealant item. This mirrors the roofing penetration convention.

Where an opening is deducted from the main plane, any clad return or reveal into the opening (the jamb, head, and sill faces), plus recessed entries, balcony soffits, and projecting bay returns, is a real surface that must be added back as a separate face, measured by area or lineally for narrow widths. Deducting the opening but ignoring the clad return is the most common net-area error on rainscreen. Eave and rake soffit area and fascia length are also routinely taken with the siding scope as a sibling class, with soffit area equal to the overhang width times the eave and rake run and fascia length equal to that run.

Fasteners are a real consumable quantity driven by the code or manufacturer nailing schedule. Fiber-cement fastening follows IRC Table R703.3(1) or R703.3.2, and vinyl follows IRC R703.11, with high-wind zones tightening the spacing per the manufacturer high-wind details. The fastener count equals the board or panel count, or the course length, times the fasteners per unit from the schedule.

Metal wall panels are priced by weight and by panel and seam quantities. Net area converts to weight through the steel gauge weight factor, about 40.8 pounds per square foot for each inch of base-steel thickness, taken from the AISI gauge table with the ASTM A653 base-metal-thickness basis. Standing-seam and closure length equals the net area divided by the panel coverage width, and the panel count equals the net area divided by the panel length times the coverage width.

EIFS is measured like other cladding. ASTM C1397 governs its application but publishes no estimating method, so the net elevation area of the finished face, with insulation board, base coat, and finish taken as one system, is used, with openings deducted over the regional void threshold. Aesthetic reveals and banding, the grooved foam shapes, are taken as linear items rather than extra area.

Waste belongs only in the ordering quantity, never in the measured boundary. The common siding bands run about 10 percent for simple rectangular walls and around 15 percent for cut-up work, driven up by gables, many corners and openings, and diagonal cuts. These bands are estimating and manufacturer practice rather than a numbered clause, so they should be set to suit the job.

Which quantity an output represents depends on its purpose. Bid, progress billing, and cost control use the net measured area, openings deducted per the regional void rule and no waste. Procurement ordering uses the net area times one plus the waste percentage, rounded up to the next square, carton, or box. Commonwealth measured bills keep waste out of the quantity and inside the unit rate, while US ordering puts it in. A quantity should never carry a waste percentage and a waste-loaded rate at once. Exayard reads the drawings and applies these rules automatically, tracing each elevation to its outer corners, carrying the gable to the peak, converting net area through exposure, and producing the cladding, trim, barrier, and flashing quantities for the system and region in use.