Estimating in Building Construction

Concrete 109

floors include hand or machine troweled, carborundum
rubbing (machine or hand), wood float, broom, floor hard-
eners, and sealers. Walls and ceilings may also be troweled,
but they often receive decorative surfaces such as bush ham-
mered, exposed aggregate, rubbed, sandblasted, ground, and
lightly sanded. Finishes such as troweled, ground, sanded,
wood float, broom finishes, and bush hammered require no
materials to get the desired finish, but require only labor and
equipment. Exposed aggregate finishes may be of two types.
In the first type, a retarder is used on the form liner, and then
the retarder is sprayed off and the surface is cleaned. This
finish requires the purchase of a retarding agent, spray
equipment to coat the liner, and a hose with water and
brushes to clean the surface. (These must be added to mate-
rials costs.) The second method is to spray or trowel an
exposed aggregate finish on the concrete; it may be a two- or
three-coat process, and both materials and equipment are
required. For best results, it is recommended that only expe-
rienced technicians place this finish. Subcontractors should
price this application by the square foot.
Rubbed finishes, either with burlap and grout or with
float, require both materials and labor hours plus a few hand
tools. The burlap and grout rubbed finish requires less mate-
rial and more labor than the float finish. A mixer may be
required to mix the grout.
Sandblasting requires equipment, labor, and the grit to
sandblast the surface. It may be a light, medium, or heavy
sandblasting job, with best results usually occurring with
green to partially cured concrete.
Bush hammering, a surface finish technique, is done to
expose portions of the aggregates and concrete. It may be
done by hand, with chisel and hammer, or with pneumatic
hammers. The hammers are commonly used, but hand chis-
eling is not uncommon. Obviously, hand chiseling will raise
the cost of finishing considerably.
Other surface finishes may also be encountered. For
each finish, analyze thoroughly the operations involved,

material and equipment required, and labor hours needed to

do the work.

The finishing of concrete surfaces is estimated by the

square foot, except bases, curbs, and sills, which are esti-

mated by the linear foot. Since various finishes will be

required throughout, keep the takeoff for each one sepa-

rately. The labor hours required (approximate) for the vari-

ous types of finishes are shown in Figure 10.30. Charts of

this type should never take the place of experience and com-

mon sense, and are included only as a guide.

Materials for most operations (except exposed aggre-

gate or other coating) will cost only 10 to 20 percent of labor.

The equipment required will depend on the type of finishing

done. Trowels (hand and machine), floats, burlap, sandblast-

ing equipment, sprayers, small mixers, scaffolding, and small

hand tools must be included with the costs of their respec-

tive items of finishing.

Estimating Concrete Finishing. Areas to be finished

may be taken from other concrete calculations, either for the

actual concrete required or for the square footage of forms

required.

Roof and floor slabs, and slabs on grade, pavements,

and sidewalk areas can most easily be taken from the

actual concrete required. Be careful to separate each area

requiring a different finish. Footing, column, walls, beam,

and girder areas are most commonly found in the form

calculations.

EXAMPLE 10-16 CONCRETE FINISHING

Using the concrete takeoff from Example 10-7, the needed infor-

mation for determining the quantity of concrete to be finished can

be found. From that takeoff, the following information can be

gleaned:

5,162 sf 

Area of slab (sf )4,427 sf of 6– slab735 sf of 2– topping

FIGURE 10.30.Concrete Finish Labor Productivity.

Labor Hours/

Finish Method/Location 100 s.f.

Troweling Machine—Slab on Grade 1.0

Hand—Slab on Grade 2.0

Broom Finish Slabs 0.75

Stairs 4.0

Float Finish Slab on Grade 3.5

Slabs Suspended 4.0

Walls 3.5

Stairs 3.0

Curbs 8.5

Bush Hammer Machine—Green Concrete 3.0

Machine—Cured Concrete 6.0

Hand—Green Concrete 9.0

Rubbed With Burlap and Grout 2.5

With Float Finish 4.0