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 Hours per Square Ft method for specialty ducts (PVC, FRP, Fiberglass, Flex etc.). The Hours Per Piece method are 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 size and type 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 or the experience of the estimators knowledge of the sheet metal fabrication process and associated labor and installation experience. The important consideration with this method is that labor will vary, in some cases significantly with variations in ductwork type and size. As mentioned each piece of ductwork in a takeoff is evaluated to calculate labor and material cost. 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 low pressure galvanized productivity rate of 44 lbs. per hour or conversely " hours per pound" of ductwork fabricated or installed". If you use this formula take 44 lbs per hour divided into 1=.023 hrs per lb. An estimator can develop a formula based on specific shop conditions and methods dependent upon the level of automation utilized and shop skill level utilized. The Square Ft Per Hour Method is a useful way to compare labor cost for different types and gauges of ductwork for 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. The methods and examples provided provide a framework to assist estimators for quantifying labor and material cost.
