Methods for calculating Ductwork Labor
There are several methods to calculate ductwork labor cost however, we will cover three of the most commonly accepted methods that provide consistent and accurate results are: The Hours per Piece Method, The The Hours Per Lb. Method and The Hours per Square Ft method for specialty ducts (PVC, FRP, Fiberglass, Flex etc.). The Hours Per Piece method is based on the actual amount of labor that is required to fabricate or install each specific piece and type of ductwork, predetermined and applied to the various sizes and types of ductwork in a takeoff. On this basis variations in the size and type of each piece of ductwork fitting and duct are considered as part of the labor calculation formula. This method is based on labor studies for the various types and sizes of ductwork fabricated and the experience of the estimators knowledge of the sheet metal fabrication process and associated labor and installation. Production labor studies are most often used as the basis for determining labor cost. The important consideration with this method is that labor will vary, in some cases significantly with variations in ductwork type and size. The Pounds Per Hour method for calculating labor is based on hours per pound of fabrication and installation labor productivity. As an example we will use a typical example of low pressure galvanized ductwork productivity at a rate of 44 lbs. per hour or " hours per pound" of ductwork fabricated or installed". If you use this formula you take 44 lbs per hour divided into 1=.023 hrs per lb.With this basic method an estimator can develop a formula for calculating shop labor. The Square Ft Per Hour Method is a useful way to compare labor cost for different types and gauges of ductwork as a direct comparison independent of per piece calculations or pounds per hour formulas. If you convert a typical 24 gauge low pressure galvanized ductwork productivity rate into square ft. using this formula you would calculate: 44 lbs per hour/1.156=38 square ft. per hour and install rate 25 lbs. per hour/1.156= 22 SF/hr. This basic formula can be used to cross check the hours per pound method and square ft. per pound method. The methods and examples provided provide a framework to assist estimators to quantify labor and material cost.
Calculating installation labor and material pricing for piping, fittings, valves and specialties is a function of several system type characteristics. As an example there are categories of material types; Black iron, copper, stainless steel, cast iron, plastic polybutylene, high density, polybutylene, brass. There are many other material types used but the most common plumbing material types are PVC, CPVC and PEX. Items are broken down based on either pipe or fitting type. Sizes ranges are most commonly from 1/2" to 3" diameter. Connection types are threaded, welded, flanged etc. Hanger types are band, ring, clevis, etc. The estimate should be broken down in labor and pricing tables, and on extension sheets based on material type, item type, sizes, connection type and hanger type. Hangers usually are not considered a fundamental category but should be listed separately. The takeoff may be broken down in categories so that correction multipliers may be applied based on project conditions. Project conditions may be applied based on standard floor plans, tight space, congested areas, elevated piping runs, equipment rooms, etc. with a breakdown based on different material types and system types; hot water heating, black steel, schedule 40 etc. and refrigeration system. Equipment hook ups should be taken off separately and equipment duplications may be treated as an assembly and multiplied by the number of equipment hook ups. Estimate the hookups separately. Typically non-productive labor is not included with labor however, material handling should be included when calculating total labor. Job condition multipliers may be applied and calculated separately to account for installation variations.