Electrical takeoff

A conduit run is measured along the centre line of the run, from the geometric centre of one enclosure to the centre of the next, not the box faces. Stopping at a face drops the pipe inside each enclosure, a loss that repeats on every run. RICS NRM2 Work Section 39 measures services net along the centre line, and ANZSMM enumerates points between boards along the route. Conduit is routed at right angles, parallel to walls and structure, never on a diagonal, so measuring the straight-line hypotenuse is the most common cause of under-measurement: sum the orthogonal legs along the actual route.

Nothing is deducted from a raceway run. The centre line passes straight through every fitting and into each enclosure, and boxes and fittings are counted as separate items rather than subtracted. The only adjustments are additions: a small allowance per bend for the take-up of the radius, and the vertical legs below.

A floor-plan trace captures only the horizontal part of the run. The raceway also drops to each device, climbs risers up walls and columns, and stubs up through slabs. These vertical legs are invisible on plan and are the most-missed conduit quantity, so they must be added; standard methods measure the developed, fully installed length. Feeders, risers, and the service entrance must be read off the one-line and riser diagrams, since the vertical pipe between distribution levels does not appear on a plan view.

Drop heights come from the project mounting-height schedule when one is given. Otherwise, trade practice centres a receptacle box at about 18 inches above finished floor and a switch box at about 48 inches; the NEC sets no fixed general-use mounting height. Accessibility rules set the band, not the default: ICC A117.1 and the ADA Standards require accessible operable parts within a reach range of 15 to 48 inches above finished floor. In the UK, Approved Document M places the centre line of switches and socket outlets between 450 and 1200 millimetres above finished floor in new dwellings, and national accessibility codes elsewhere set their own bands.

The NEC limits the total bends between pull points to 360 degrees, the equivalent of four quarter-bends, set in the .26 section for each raceway type: 358.26 for EMT, 344.26 for rigid metal conduit, 342.26 for intermediate metal conduit, 348.26 for flexible metal conduit, 352.26 for PVC, and 362.26 for electrical nonmetallic tubing. When the route plus offsets would exceed 360 degrees, a pull box must be inserted. A pull box splits the run into two separately measured segments and adds one enclosure to the count; pull boxes are counted each and never measured into the conduit length. The UK (BS 7671) and Australia and New Zealand (AS/NZS 3000) reach the same intent through required draw-in and inspection boxes rather than a fixed degree figure.

Never reuse conduit length as wire length. Conductors continue past the end of the conduit into each enclosure for terminations and splices, so wire footage always exceeds conduit footage. The NEC requires at least 6 inches (150 millimetres) of free conductor at every outlet, junction, and switch point, and large boards and switchgear need extra slack for make-up; in the UK, BS 7671 calls for adequate conductor length at accessories, with a tail of roughly 150 millimetres typical and larger loops at boards. Wire is then multiplied by the number of conductors in each raceway, since one conduit carries several, and carries its own allowance for reel-end cut-offs, pulling spoilage, and termination loops. Only the per-box minimum is fixed by code; the larger make-up loops at panels and switchgear are practical allowances.

There are two accepted ways to measure circuits. The detailed method traces every box-to-box segment and sums them: most accurate, slowest, and the right choice for procurement and ordering. The homerun-plus-average method measures the homerun from the panel to the farthest device, then adds an average footage per device for the daisy-chained branch; it is faster and common in early US bidding. That average footage is not fixed by any standard, varying widely with occupancy (residential, commercial, or industrial), ceiling height, and device density, so it should be treated as a tunable figure calibrated against project history. In the United States, labour is applied through the NECA Manual of Labor Units, which prices installed raceway per 100 feet with normal, difficult, and very difficult tiers.

Device counts feed both fixture procurement and the branch-circuit derivation, so they are counted by device and segregated by schedule type. Receptacles are counted by device: a duplex is one, and special-purpose receptacles (range, dryer, 208 to 240 volt), GFCI, weatherproof, and floor boxes are each separate count lines by type. Switches, luminaires, data and AV jacks, and blank junction boxes are excluded. In the UK and in Australia and New Zealand, socket outlets are often enumerated by gang, so a twin socket is one accessory but two outlets.

Switches are counted per yoke or strap, not per box, so a three-gang bank counts as three. A multi-way control has a device at each end and both are counted: the US three-way and four-way are the UK two-way and intermediate. Dimmers, occupancy sensors, and timers are separate count lines. Luminaires are counted each by their fixture-schedule type tag; a 2 by 4 troffer is one fixture even though it may displace several ceiling tiles. Continuous strip, cove, and row fixtures can instead be measured in length by type, and exit signs, emergency lights, and exterior fixtures are separate lines. Standards distinguish the lighting point (the wiring outlet) from the luminaire (the fitting), and NRM2 and ANZSMM enumerate both.

Distribution equipment is a distinct enumerated item, separate from devices, fixtures, and raceway. Each panelboard, switchboard, switchgear lineup, or distribution board is counted, described by type, number of ways or poles, and rating. RICS NRM2 enumerates boards by number with their way count and rating, and ANZSMM lists them on the distribution schedule. Read this off the one-line and riser diagrams, never the floor plan, because each board is a high-cost line that is easy to omit.

Grounding and bonding is its own system under NEC Article 250: the grounding-electrode conductor, the electrodes (rods, plates, or a concrete-encased electrode), bonding jumpers, and the equipment-grounding conductor pulled with each raceway all add quantity that counting phase and neutral conductors will miss. The equipment-grounding conductor adds wire footage unless the metallic raceway itself serves as the ground, and the electrode hardware is a separate enumerated item; in the UK, BS 7671 measures circuit protective conductors and main bonding separately by size and type.

Cable tray, busway and bus duct, wireway, and surface raceway are measured differently from conduit and must not be folded into conduit length. They are measured in length by system, size, or rating, stating jointing, spacing, and supports, with their fittings (elbows, tees, tap-off boxes, end feeds, and supports) enumerated separately. RICS NRM2 measures tray and trunking in metres stating jointing, spacing, and supports, and busbar trunking by length and rating; the relevant NEC articles are 392 for cable tray, 368 for busway, and 376 and 378 for wireways.

Underground electrical is measured in length by configuration, stating the number and size of ducts, while the trench excavation, bedding, backfill, and concrete encasement are measured separately by burial-depth band. NEC Table 300.5 sets the minimum cover by wiring method and circuit type, which fixes the depth band. Because the trench often belongs to the site-utilities scope, take it off in exactly one place to avoid double-counting, and add a concrete-volume line where the duct bank is encased.

Retrofit and renovation work classifies each item into one of three states: existing-to-remain (no takeoff), remove (a demolition line measured for removal labour and disposal), and reuse (existing raceway or boxes re-pulled). Reusing an existing raceway reduces new conduit length but still needs new wire pulled through it. RICS NRM2 measures removal and alteration as separate items from new installation. Drive this from the existing-conditions survey, not the plan alone.

Branch wiring and feeders are taken off separately. Branch circuits use small conduit and wire to devices; feeders, risers, and the service entrance use large conduit and wire between gear, with very different sizes, labour rates, and routing, so merging them corrupts the estimate. Branches come off the floor plan; feeders, risers, and service come off the one-line and riser diagrams. Segregate conduit by raceway type (EMT, rigid, intermediate, PVC, or flex) and trade size as well, since each carries its own material and labour rate.

Raceway is a linear quantity: imperial regions measure conduit in linear feet, with NECA labour priced per 100 feet, and metric regions in linear metres along the centre line, in each case segregated by raceway type and trade size and rounded to the region's convention. Ordering allowances apply to material quantities only, never to the measured boundary or to billed-in-place quantities. Conduit carries a waste allowance for cut-offs, bend spoilage, and damaged sticks, often around 10 percent and higher on bend-heavy runs, and wire carries a slightly higher waste-and-make-up allowance because of pulling loss and termination loops. These percentages are practical ordering allowances, not standard figures, so calibrate them against project history.

Regional methods differ in emphasis. The United States has no statutory method, works to NEC-anchored convention in imperial units, and tolerates the homerun-plus-average shortcut. The UK is the most codified: RICS NRM2 Work Section 39 measures services net along the centre line in metres, enumerates accessories and luminaires by number, and separates final circuits from sub-mains, with BS 7671 governing draw-in boxes and conductor tails. Australia and New Zealand follow ANZSMM with a distribution-schedule approach that enumerates every point by location and type, metric throughout. Canada is hybrid: metric drawings, imperial trade sizes, NEC-aligned practice, and British-origin quantity-surveying methods. European countries use national methods such as the DIN-based German standards, metric, with device heights set by national accessibility norms. International work harmonises on ICMS, measuring services in centre-line metres. Exayard reads the plan set, the one-line, and the schedules, applies these rules by raceway type and device type, and records the standard behind each quantity so it can be checked and defended.