Landscaping and irrigation takeoff

Planting beds, sod, seed, and hydroseed are traced to the net outline of the surface actually treated: the bed edge, lawn limit, or seed limit shown on the plan. Everything inside that envelope that is not planted is deducted at its edge: buildings, paving, water features, existing trees to remain, and large rock areas. Small voids are not deducted. RICS NRM2 Section 35 (site works and paving) carries a void threshold of 1.00 square metre, about 10.76 square feet, raised from SMM7's 0.50 square metre, applied to soft landscaping by analogy. US private practice is looser and lets waste absorb smaller penetrations.

Sod and seed share the same plan polygon; only the material derivation differs. Sod is reported by the square yard placed, seed as a weight from net area times a per-area seeding rate, and hydroseed by area or tank load. Highway specifications measure sod by the square yard surface measure and seeding by the acre or by the square (100 square feet). For conventional seeding, seedbed preparation, seed, and mulching and anchoring are separate items; only hydroseed combines them into one slurry rate. On slopes, the default is the horizontal plan projection unless a specification calls for surface area on steep cut or fill; on a 2:1 or steeper slope the true surface can be 10 to 40 percent larger.

Mulch, topsoil, and amendment are volumes derived as net bed area times depth. The geometric constants are exact: one cubic yard covers 324 square feet at 1 inch, 162 square feet at 2 inches, and 108 square feet at 3 inches, from 27 cubic feet per cubic yard times 12 inches per foot. The value at 3 inches is exactly 108, not 100. The default bed-mulch depth is 2 to 3 inches when the plan does not state one.

Topsoil for lawns spreads about 4 inches on flat ground and about 2 inches on a 3:1 slope; planting-pit backfill is a separate volume item. Loose topsoil settles when placed, so a settlement uplift of about 1.20 to 1.30 times the placed volume is added to the loose order (about 1.15 for sandy topsoil), matching loam swell of roughly 20 to 30 percent. Soil amendment (compost, lime, fertilizer) is a separate measured item. Decorative gravel lays loose, but a compacted aggregate base under paving needs a loose-to-compacted allowance of about 15 to 25 percent.

Trees and individual specimen shrubs are a pure count taken off the plant symbol or schedule, never derived from area. Mass plantings (groundcover, perennials, hedges) are derived from bed area divided by area per plant. Either way, plants are enumerated segregated by species and by size, caliper, or container class, because RICS NRM2 Section 37 and highway plant pay items bill by size class.

With square (grid) spacing, area per plant is the on-center spacing squared, so plants per square foot is one divided by the spacing in feet squared: 4 at 6 inches, 1 at 12 inches, 0.25 at 24 inches, and 0.11 at 36 inches. With triangular (staggered) spacing, area per plant is the spacing squared times 0.866, which fits about 15 percent more plants at the same spacing. Triangular is the default for naturalistic mass plantings, square for formal grids and rows.

Subtract overstory trees from the understory count where the canopy displaces groundcover. Plant material carries a small over-order of about 5 to 10 percent for mortality and handling; in UK NRM2 practice, replacement is instead carried in the establishment, maintenance, and defects period as a separate item or sum. Planting-pit excavation and amended backfill are a per-plant volume item (the pit is about 2 to 3 times the rootball width at rootball depth), and staking, guying, tree grates, and root barriers are per-tree accessories counted off the tree total.

Irrigation pipe is a centerline developed-length takeoff, measured like plumbing. Mainline and laterals run on the pipe centerline through every fitting without shortening; risers, swing joints, and depth-of-bury verticals are added; the run is segregated by size and class (mainline PVC, poly lateral, drip tubing). Fittings, valve boxes, quick-couplers, and flush-caps are their own count. Sleeving under paving is a separate linear item, a carrier pipe inside a larger sleeve extended past each paving edge. The low-voltage control wire from controller to valves is also a linear item: one common plus one conductor per valve.

Heads, emitters, valves, controllers, and backflow devices are each counts. Where heads are derived from spacing, the head-to-head rule governs: no more than 50 percent of the throw diameter for a square pattern, so each head throws to the next. Triangular layouts relax to about 55 to 60 percent of the diameter, and narrow single-row strips tighten to about 40 percent of the radius; a triangular layout needs fewer heads for equal coverage. The 50-percent square figure is codified by Florida Water Star; ASABE/ICC 802 governs the emission device, not the layout. Drip emitters are counted per plant by size, such as two 1-gallon-per-hour emitters per shrub and three or four around a large tree's dripline. Zone count is total head flow divided by usable supply flow, commonly about 75 percent of available flow with meter loss held to no more than 10 percent of static pressure.

Erosion-control blanket and turf-reinforcement mat are measured by area (square yards or square metres) with a seam and anchor overlap, and silt fence and perimeter controls by linear foot. For hydroseed on steep slopes, a bonded fiber matrix is applied at 3,000 pounds per acre or more at about 10 percent tackifier, roughly 90 percent wood fiber and 10 percent bonded adhesive by weight; flat or gentle ground takes 1,500 pounds per acre or more at about 3 percent tackifier. Tree protection is fencing by linear foot around each protection zone plus a count of protected trees. Bed edging is a linear-foot item along the bed line: a material item for an installed steel, poly, aluminum, or concrete restraint, but labor-only for a spade-cut bed line.

Hardscape (segmental pavers, flagstone, walls, edging) reuses the paving conventions: the paved face is traced to the outer edge restraint or soldier course as an area. Pattern-based paver waste is added by layout: running bond about 5 to 10 percent, basketweave about 8 to 12 percent, herringbone about 10 percent at 90 degrees and 18 percent at 45 degrees, and circular patterns highest at about 22 percent, all trade practice informed by the Interlocking Concrete Pavement Institute. The base aggregate (compacted, depth set by load) and the bedding sand of about 1 inch beneath the pavers are separate volume items, distinct from the paver face area.

In the United Kingdom and Ireland, RICS NRM2 governs: cultivating, seeding, and turfing in square metres, imported topsoil in cubic metres, plants enumerated, the 1.00 square metre void rule, and net measurement, with CESMM4 for civil and highway work. Australia and New Zealand follow the AIQS and New Zealand methods of the same RICS lineage. The United States has no legal method: private work lets waste absorb small voids, while public work follows highway specifications (sod by the square yard, seeding by the acre or square, plants each, imperial units). Canada is a hybrid CIQS net measure with metric drawings and imperial materials. In the European Union, national methods apply, with DIN 277 classifying area and German work following VOB Part C. International practice follows the ICMS and IPMS baseline, metric and net.

The same plan produces different numbers depending on why the takeoff exists. The net measured quantity, for bidding and billing, applies the void thresholds and adds nothing. The ordered quantity, for procurement, adds waste and over-order only at this stage: sod about 5 to 15 percent, plants about 5 to 10 percent, mulch about 10 percent, and irrigation pipe about 5 to 10 percent, plus the topsoil settlement uplift and the base-aggregate compaction allowance. Reporting an order quantity as a billing quantity over-bills the owner; reporting a net quantity as an order under-supplies the work.