Part of making plans for new home construction is estimating the quantity of each of the various building materials needed to complete the project. First, you'll need to decide the primary mode of construction (for example, wood framing versus concrete block). Keep in mind that minor variations in material selection (asphalt vs. wood shingles) will impact the cost. This article will discuss simple ways to calculate the volume or quantity of each of the principal building components of a wood-frame house.
Estimate the Volume of Concrete Needed for the Foundation
Calculate the amount of concrete needed to build the foundation by dividing the foundation into the most basic rectilinear volumes. A slab on grade would consist of a slab and a grade beam along the length of the perimeter. A foundation surrounding a full basement contains a slab, foundation walls, and the footings on which they rest. Calculate the volume of a slab by multiplying the length by the width by the thickness.
The volume of grade beams, footings, and foundation walls is found by first multiplying the depth (or height) by the width to get the cross-sectional area. Then multiply the area by the total length of the foundation perimeter to get the volume. Add the volume of each component to get a total of the units of cubic feet. Then divide this number by 27 cubic feet to get a volume in cubic yards.
Estimate the Required Framing Lumber
Determine the total linear length in feet of all the walls in the building, both exterior and interior and convert this total to inches. Then divide by 16 to get the approximate number of 2 by 4 wood studs needed to frame the walls. Increase this number by an additional 100 studs to account for trimmers, corners, and blocking. Multiply the combined wall length by 3 to get the linear (10 feet or longer) 2 by 4 lumber needed for the wall plates.
Consult the architectural plans for the dimensions and lengths of the major structural members like rafters and joists. A gable ridge board will need a joist and a pair of rafters spanning the width of the house for each 16-inch increment. For large houses with complex roofs, the size and quantity of rafters and joists can easily be tabulated by examining the framing plans in the construction documents. You will also need some of the larger structural members to make headers and beams.
Estimate the Area for Sheathing, Shingles, and Sheetrock
Plywood sheathing comes in 4 by 8-foot sheets and is installed onto every exterior surface of the house including the roof. Simply calculate the total area of the exterior walls and add it to the combined area of each roof plane to get the total sheathed area in square feet. Then divide the total area by 32 square feet to get the number of plywood sheets needed.
Do the same for sheets of sheetrock by calculating the surface area to be sheetrocked and divide by 32 square feet. Lastly, roof shingles are purchased and installed in units called squares, each of which covers an area of 100 square feet. Estimate the number of squares needed to shingle the total roof surface area.