How to Estimate Excavation and Backfill

Backfill for Figure

  1. Backfill volume = excavation volume – footing volume – wall volume. …
  2. (Note that only the portion of the wall that is in the trench is deducted, so the height of wall in the trench is the average trench depth minus 2′-0” for the footing: 6′-0” – 2′-0” is 4′-0”)
  3. Backfill volume = 207.4 cubic yards.

For example, find the cubic footage volume of a backfill area that is 8 feet wide, 6 feet deep and 50 feet long. The volume of a rectangular cubed shape is found by the formula v = l x w x d, where v represents volume, l is the length of the trench, w is the width and d is the depth.

How do you calculate excavation?

So, the formula is: Ab = Wb * Lb, where Wb and Lb are the width and length of the bottom of the excavation. At = Wt * Lt, where Wt and Lt are the width and length of the top of the excavation. 

How do you calculate excavation cost?

The cost of excavation is generally estimated by multiplying the total excavation volume to the excavation price per unit. For ex : Let us assume that you want to excavate a pit of size : 2 x 2 x 2 meter. The market price for excavation is 10$/cu. m.

In this case the total volume of excavation is 8 cu.m. The cost of the excavation will be 8*10= 80$

How do you calculate dirt excavation?

Add the length at the top of the excavation to the length at the bottom of the excavation and divide by 2 to get the average length. Do the same for the width. Multiply the average length times the average width times the average depth and divide by 27.

How is earthwork excavation quantity calculated?

To calculate the earthwork estimate requires multiplying the area by the difference between the average of two sets of levels. Formula: Volume = Area * Difference between the average of two sets of levels.

Getting an Estimate

Because excavation can be a costly necessity, it’s important to get your quote in writing and to work with a contractor that is licensed and insured—cutting corners will end up costing significantly more in the long run and could lead to an unsafe building.

Here are a few guidelines to follow when choosing a contractor for your commercial excavation:

  •      Hire one contractor who can perform lot clearing, demolition (if necessary), excavation and backfill work. Working with one company on both lot clearing and excavation can expedite the process, which can easily get derailed by slow-moving communication. You’ll also avoid paying multiple base or new client fees.
  •      Work with a contractor that’s been around for a while. More experienced contractors will better understand the challenges you can expect. For example, lots in the Pacific Northwest often require significant tree removal and specialized excavation techniques to combat challenges that arise when encountering perpetually wet soil.
  •      Choose a contractor that doesn’t charge extra for holiday and weekend work. Ask this question up front and move on if the answer is yes. These added costs multiply quickly and there are plenty of reputable companies that won’t take advantage of you.
  •      Ask if the company owns the necessary equipment to get the job done. If not, make sure you’re informed upfront about any additional rental costs.