Estimating in Building Construction

Excavation 87



9–12 Excess and Borrow

Once the earthwork has been calculated in terms of excava-
tion, backfill, and grading, the estimator must compare the
total amounts of cut and fill required and determine
whether there will be an excessof materials that must be dis-
carded, or whether there is a shortage of materials and some
must be brought in (borrow).Topsoil is not included in the
comparison at this time; topsoil must be compared sepa-
rately because it is much more expensive than other fill that
might be required, and the excess topsoil is easily sold.
Shrinkage and swell must also be taken into account.
The specifications must be checked for what must be
done with the excess material. Some specifications state that
it may be placed in a particular location on the site, but
many times they direct the removal of excess materials from
the site. If the material is to be hauled away, the first thing the
estimator must know is how many cubic yards are required;
then the estimator must find a place to haul the material.
Remember that soil swells; if the estimator calculated a haul
of 100 bcy and the swell is estimated at 15 percent, 115 lcy
must be hauled away. Finding where the excess material can
be hauled is not always a simple matter, because it is desir-
able to keep the distance as short as possible from the site. If
the haul distance is far and/or there is a restriction on the
number of available dump trucks, the haul time may dictate
the excavation equipment cost rather than the actual
amount of earth to be removed. If the backhoe or the front-
end loader has to wait for the truck to load, the equipment
and operator costs are incurred for the wait time even
though no productive work is being performed. The estima-
tor should check into this when visiting the site. If material
must be brought in, the estimator must first calculate the
amount required and then set out to find a supply of mater-
ial as close to the job site as is practical. Check the specifica-
tions for any special requirements pertaining to the type of

Volume of backfill (ccf )7,593 ccf>27 cf per cy281 ccy

Volume of backfill (ccf )24.68 sf307.67¿7,593 bcf

Fill area (sf )(5.34 sf4 sf3 sf) 2 24.68 sf

soil that may be used. Keep in mind that the material being

brought in is loose and will be compacted on the job. If it is

calculated that 100 ccy are required, the contractor will have

to haul in at least 110 to 140 lcy of soil—even more if it is

clay or loam.

The next step is to select equipment for the work to be

done, which will depend on the amount of material, type of

soil, and the distance it must be hauled.

9–13 SPREADING TOPSOIL,

FINISH GRADE

Many specifications call for topsoil to be placed over the

rough grade to make it a finish grade.The topsoil that was

stockpiled may be used for this purpose, but if there is no

topsoil on the site, it will have to be purchased and hauled

in—a rather costly proposition. The estimator must be cer-

tain to check the specification requirements and the soil at

the site to see whether the existing soil can be used as topsoil.

On most projects, the equipment needed for finish grading

will consist of a bulldozer or a scraper. The quantity of top-

soil is usually calculated by multiplying the area used for

rough grading by the depth of topsoil required.

After the topsoil has been spread throughout the site in

certain areas, such as in the courtyards, around the build-

ings, or along the parking areas, it is necessary to hand rake

the topsoil to a finish grade. The volume of soil to be moved

must be calculated and entered on the estimate.

9–14 Landscaping

Most specifications require at least some landscaping work. If

the work is seeding and fertilizing, the general contractor

may do it or subcontract it out. The estimator should check

the specifications for the type of fertilizer required. The spec-

ifications may also state the number of pounds per square

(1 square = 100 sf ) that must be spread. The seed type will be

included in the specifications, which will also state the num-

ber of pounds to be spread per square. Who is responsible for

the growth of grass? If the contractor is, be certain that it will

receive adequate water and that the soil will not erode before

the grass begins to grow. Often the seeded area is covered

with straw or special cloth, which helps keep in moisture and

reduce erosion. The estimator will have to calculate the area

to be fertilized and seeded, determine what equipment will be

used, arrange covering and water, and then arrange the

removal of the covering if it is straw.

Sodding is often required when the owner wants an

“instant lawn.” The specifications will state the type of sod

required, and the estimator must determine the area to be

covered. The general contractor or a subcontractor may han-

dle this phase of work. The estimator, in calculating labor

costs, must consider how close to the actual area being sod-

ded the truck bringing the sod can get, or whether the sod

will have to be transferred from the truck to wheelbarrows

or lift trucks and brought in.

FIGURE 9.41.Alternate Backfill Method.