Quck answer
To calculate the amount of retaining wall materials needed for your landscaping project, follow these steps:
1. Measure the length and height of the retaining wall in feet.
2. Determine the desired thickness of the wall in inches.
3. Convert the thickness to feet by dividing the inches by 12.
4. Calculate the volume of the wall by multiplying the length, height, and thickness in feet.
5. Determine the type of material you will use for the wall (e.g., concrete blocks, timber, stone).
6. Consult the manufacturer’s specifications to determine how many units of the chosen material are needed for one square foot of wall.
7. Multiply the volume of the wall by the number of units needed per square foot to get the total number of units required.
8. Add extra units for waste and breakage.
9. Purchase the calculated amount of retaining wall materials to ensure you have enough for your project.
For DIY landscapers constructing a retaining wall, it is crucial to have accurate estimates of the amount of stone blocks, cap stones, and gravel required for the project. By obtaining a landscaping estimate, you can effectively plan for the cost of materials and labor needed to build the retaining wall, ultimately saving both time and money.
The quantity of stone blocks and gravel necessary depends on the wall’s dimensions and the depth of the backfill space behind it. The following steps outline how to make these calculations.
Step 1
To determine the square footage of the wall’s outside face, multiply the wall’s length (in feet) by its height (also in feet). Then, multiply the result by 1.12. This takes into account that 12% of the wall’s height should be buried beneath the ground’s surface to enhance stability.
For instance, if the wall measures 24 feet in length and 2.5 feet in height, the square footage is calculated as (24)(2.5)(1.12) = 67.2 sq.ft.
Step 2
Calculate the square footage of each stone block’s outside face by measuring its area in square inches and dividing the result by 144 to convert it to square feet.
For example, if each stone block is 10 inches wide and 6 inches tall, the square footage of each stone face is determined as (10)(6)/144 = 0.4167 sq.ft.
Step 3
Divide the square footage of the retaining wall’s face by the square footage of each stone’s face to obtain the total number of stones needed.
Using the given numbers as an example, we would require 67.2/0.4167 = 162 blocks. It is advisable to purchase some extra blocks to account for breakage.
Step 4
Estimate the amount of gravel needed to fill the trench at the base of the retaining wall. If the wall’s dimensions are denoted as L feet in length, H feet in height, and T inches in thickness, the trench’s dimensions should be L feet in length, 0.12H feet in depth, and 2T inches in width.
In terms of cubic yards, the trench’s volume is calculated as LHT/1350, and approximately half of this volume will be filled with coarse gravel. Consequently, the cubic yards of gravel required for the base is LHT/2700.
For example, if the wall measures 24 ft. in length, 2.5 ft. in height, and 8 inches in thickness, we will need (24)(2.5)(8)/2700 = 0.1778 cubic yards of gravel for the base.
Step 5
Estimate the cubic yards of gravel needed for backfilling behind the retaining wall. Assuming there is a half-foot gap between the stones and the earth, the volume of gravel required is 0.5LH cubic feet, or LH/54 cubic yards.
For instance, for a retaining wall that is 24 feet long and 2.5 feet high, we will need (24)(2.5)/54 = 1.111 cubic yards of gravel for backfilling.
Step 6
Calculate the number of capstones needed by dividing the wall’s length in feet by the length of the capstones in inches. Then, multiply the result by 12.
For example, if the wall is 24 feet long and the capstones are 8 inches wide, the number of capstones required is 24/8 = 36. It is advisable to purchase a few extra capstones in case of breakage or the need for cutting.
