There are essentially two parts to a concrete foundation: the footer and the walls. Each part is made from the same materials. Consequently, there is no cost variation in material costs. Over time, the construction industry has developed an effective method to estimate a concrete foundation. You can utilise this method to complete an accurate estimate for your own projects.
Measure the length and width of the concrete footers. Because your foundation has not yet been poured, you may be working from a rough sketch or plans. Take the entire perimeter length of the footer and multiply it by the width. For example, if you have 100 feet of footers that are two feet wide, multiply the two to come up with 200 feet. Multiply that number by the footer thickness, which is usually 12 inches (but could be more), i.e., 200 feet times one foot equals 200. Record this number on a writing pad under a label such as "footer cubic feet."
Find the cubic feet of your foundation walls by taking the total number of feet in length, which is 100 feet long in the above example, and multiply that number by the foundation wall height, which we will call three feet, for a total of 300 feet. Convert the footage into inches since your foundation wall thickness will be eight inches thick. Multiply 300 feet by 12 inches and you get 3,600 inches. Now, multiply 3,600 inches by eight inches--the thickness of a foundation wall--to get 28,800 cubic inches. Convert the inches back to feet by dividing by 12, to get 2,400 cubic feet of cement in the foundation wall.
Add the footer and foundation cubic feet together to get 2,600 cubic feet of concrete necessary to pour the footer and foundation wall. Now you will need to convert the cubic feet into cubic yards in order to estimate the number of cubic yards of concrete necessary for the job. Do this by dividing the total feet by 27 (2,600 cubic feet divided by 27 equals 96 cubic yards of concrete to pour the foundation). The price of concrete ranges from 80 to 100 dollars per yard, as of 2011. Call you local concrete provider to get a per yard price. For example, if the concrete is 100 dollars per yard, multiply 96 times 100 to get 9,600 dollars to pour the concrete.
Things you need
- Writing pad