EXCAVATION

1. EXCAVATION

2. EXCAVATION • General Calculating quantities of work that must be excavated is one of the more difficult portions of the estimator’s task.

3. EXCAVATION • The number of cubic yards to excavate is usually easy enough to calculate, but the cost is difficult for the following reasons: • type of soil • slope of bank required • sheet-piling • water penetration

4. SPECIFICATIONS FOR EXCAVATION • When checking the specs. You should ask the following questions. • What to do with excavated material? • If removed from site, how far must it be hauled? • Is the topsoil stockpiled for future use?

5. SPECIFICATION FOR EXCAVATION • Who is responsible for any trenching required for electrical & mechanical trades?

6. CALCULATING EXCAVATION • Excavation is measured in cubic yards. • 1 cubic yard = 3’ x 3’ x 3’ = 27 c.F. • 1 cubic foot of earth weighs about 100 pounds in natural conditions.

7. CALCULATING EXCAVATION • When excavation begins, the volume of material increases or swells. • The amount of swell is generally expressed as a percentage gained above the original volume.

8. MATERIAL sand & gravel loam dense clay solid rock SWELL % 10 TO 18 % 15 TO 25 % 20 TO 35 % 40 TO 60 % PERCENTAGE OF SWELL

9. CALCULATING EXCAVATION • WHEN LOOSE MATERIAL IS PLACED & COMPACTED, IT WILL BE COMPRESSED INTO A SMALLER VOLUME. • THIS REDUCTION IN VOLUME IS REFERRED TO AS SHRINKAGE.

10. RELATIONSHIP FOR SWELLING & SHRINKAGE • 1 c.y. of undisturbed material equals 1.25 c.y. loose material (truck ) equals 0.9 c.y. compacted material ( mechanically compacted)

11. EQUIPMENT • Selecting equipment is important, and the size of the project and the equipment owned by the contractor is used to determine what type to use. • Hand digging & shoveling is always required but keep it to a minimum.

12. PERIMETERS & AREAS • Perimeter is the distance around a building. • Perimeter is usually expressed in lineal feet (l.f.) • Area is the surface of the plan of a building. • Area is usually expressed in square feet (s.f.) or square yard (s.y.)

13. TOPSOIL • Topsoil is the first material removed or stockpiled on site (stripping ). • Topsoil is measured in c.y. • Topsoil is generally removed from all buildings, walks, roadways, & parking areas.

14. TOPSOIL • A clearance around the entire basic shape must be left, usually about 5’-0” for buildings and 1’-0” for sidewalks, roadways, & parking areas. • Depth of stripping varies with locations.

15. GENERAL EXCAVATION • General excavation or bulk excavation is required for basements, roads. • Dimensions should be to the outside of footings not foundation walls. • An allowance should be made for working space beyond the footing.

16. GENERAL EXCAVATION • Determine whether the excavation will be sloped on the outside perimeter.

17. AVERAGE LENGTH OF CUT C/2 C/2 C B B C A A L GENERAL EXCAVATION FOR A BASEMENT

18. GENERAL EXCAVATION • Formula for bulk excavation of a basement • average length of cut x average width of cut x depth of cut • average length & width of cut equals: • (2 x A) + (2 x B) + (2 x C / 2) +L

19. GENERAL EXCAVATION FOR A FOUNDATION WALL

20. GENERAL EXCAVATION • Formula for trench excavation of a foundation wall • average width of cut x length of cut x depth of cut • average width of cut equals • F + (2 x B) + (2 x C / 2)

21. ASSIGNMENT • Perform takeoff on excavation & striping for your residential project