Estimating in Building Construction

Finishes 205

base coat reinforced with a mesh sheet and by applying a top
coat to form an exterior insulation and finish system (EIFS).

Specifications. The specifications should state exactly
what type of plaster is required and where. The types often
will vary throughout the project, and each must be kept sep-
arate. The number of coats, thickness of each coat, materials
used, and the proportions of the mix must all be noted. The
estimator needs to check also the type of finish required,
what trueness of the finish coat is required, the room finish
schedule on the drawings—since often finishes and the fin-
ish coat required are spelled out—and determine the acces-
sories, grounds, trim, and anything else that may be required
for a complete job.

Estimating. Gypsum plasters are usually packed in 100-
pound sacks and priced by the ton. The estimator makes the
wetwall takeoff in square feet, converts it to square yards,
and must then consider the number of coats, thickness of
coats, mixes to be used, and the thickness and type of lath
required. The amounts of materials required may be deter-
mined with the use of Figure 16.7. This table gives the cubic
feet of plaster required per 100 sy of surface.

EXAMPLE 16-5 PLASTER QUANTITY

For 100 sy of wall area, a 1/4-inch thickness over metal lath will
require the following:

(for 1/4–)



Depending on the type of plaster being used, the approxi-
mate quantities of materials can be determined. The mix
design varies from project to project and must be carefully
checked. Figure 16.8 shows some typical quantities of mate-
rials that may be required. Many projects have mixes

Use 29 cf of plaster

Add 8 cf for over metal lath

5.2 cf per 1> 16 –  4 20.8 cf of plaster

designed for a particular use included in the specifications.

Read them carefully and use the specified mix to determine

the quantities of materials required. Once the quantities of

materials have been determined, the cost for materials may

be determined and the cost per square yard (or per 100 sy)

may be calculated.

Labor time and costs for plastering are subject to varia-

tions in materials, finishes, local customs, type of job, and

heights and shapes of walls and ceilings. The ability of work-

ers to perform this type of work varies considerably from

area to area. In many areas, skilled plasterers are scarce,

meaning that the labor cost will be high and problems may

occur with the quality of the work done. It is advisable to

contact the local unions and subcontractors to determine

the availability of skilled workers. In most cases, one helper

will be required to work with two plasterers.

If the plastering is bid on a unit basis, the estimator

needs to be certain that there is an understanding of how the

yardage will be computed, as the methods of measuring vary

in different localities. The yardage may be taken as the gross

area, the net area, or the gross area minus the openings that

are over a certain size. In addition, curved and irregular work

may be charged and counted extra; it will not be done for the

same costs as the flat work.

Equipment required includes a small power mixer,

planks, scaffolds, mixing tools, mixing boxes, and miscel-

laneous hand tools. Machine-applied plaster will require

special equipment and accessories, depending on the

type used.

Labor. Subcontractors who specialize in wetwall installa-

tions do this type of work, and they may price it on a unit

basis (per square yard) or lump sum.

16–11 Lath

Lathis used as a base; the plaster is bonded to the lath.

Types of lath include gypsum tile, gypsum plaster, metal,

and wood.

The type of lath required will be specified and will vary

depending on the requirements of the project. The estimator

must read the specifications carefully and note on their

workup sheet the type of lath required and where it is

required. It is not unusual for more than one type to be used

on any one job.

FIGURE 16.7.Approximate Plaster Quantities.

FIGURE 16.8.Plaster Materials.

Maximum Amount of Volume Obtained

Aggregate, in C.F. per 100 from Mixes Shown

Mix Pounds of Gypsum Plaster (C.F.)

100 : 2 2 2

100 : 2^1 ⁄ 2 21 ⁄ 2 21 ⁄ 2

100 : 3 3 3

Aggregate weights vary. Sand 95–100 pounds per cubic foot

Perlite 40–50 pounds per cubic foot

Vermiculite 40–50 pounds per cubic foot