A block foundation can be figured accurately to save time and money.
Block home foundations require various construction materials for completion. Although there are a number of ways to calculate the amount of materials needed, the quickest, easiest and most effective way, used by the construction industry for decades, requires some measurements and mathematics. The average do-it-yourselfer can estimate a block foundation in one to two hours, depending on the size and scope of the project. Does this Spark an idea?
Instructions
Footer
1. Record the footer length, depth and width on a sheet of paper. Section off the paper into footer and foundation headings. Combine the footer lengths together to arrive at a total. For example, if you have a foundation footer that is 20 feet long and 20 feet wide, the formula for calculating footer length will be: 20 multiplied by four, or 20 + 20 + 20+ 20. Multiply the length time the width times the depth. If your footer depth is 12 inches and the width is 24 inches, then multiply 80 (footer length) times one (footer depth) times two (footer width), and you get 160.
2. Convert the cubic feet of 160 into cubic yards to determine the volume of concrete needed for the footer. Divide 160 by 27, which is one cubic yard, and you get 5.92 cubic yards. This is yardage needed to pour the footer. Find out from your local concrete supplier how much concrete is selling for per yard. National averages are usually around $100 per square yard. Round the 5.92 up to 6 since companies do not deliver in fractions--the total cost of concrete would be roughly $600.
3. Calculate the rebar for the footer by taking the total footer length and multiplying by two, which is how many sticks wide the rebar will be in the footer trench. In this example, the 80 feet above multiplied by two totals 160 feet of rebar, which is sold in 20-foot lengths. Divide 160 feet by 20 -- you will need eight sticks of rebar. Rebar varies in cost, so figure $8 dollars per 20-foot-thick piece of rebar. Your total cost would be $64 dollars.
Foundation
4. Record the foundation length under the foundation section on your paper. This length will be the same as the footer length, which was 80 feet in the example. Convert the length from feet to inches by multiplying the feet times 12, which is how many inches in a foot, and you have a footer that is 960 inches long. Divide that by 16 inches, which is the length of one block, and you will need 60 blocks to run one course of concrete blocks.
5. Determine the height of the block foundation and record that under a separate heading called foundation height. The typical height of a block foundation ranges from 32 to 48 inches. Divide the wall height by eight inches, which is the height of one block. The total height will be six inches, if you are installing a 48-inch foundation.
6. Multiply the total number of blocks long times the total number of blocks high to get the total number of blocks in the foundation and you get 360 in the above example. Multiply 360 time .05, which is the amount of estimated waste, and add that to 360(378) to get a total block count. Divide the total block count by three, which is the amount of mortar needed per 100 blocks, to get mortar totals.
Tags: footer length, block foundation, height block, number blocks, total number
