Estimating in Building Construction

184 CHAPTER FOURTEEN

pieces must be carefully taken off. If felt is used under the
tile, its cost must also be included in the estimate of the job,
and furring strips must be installed for certain applications.
As unfamiliar installations arise, the estimators may call
the manufacturer, the manufacturer’s representative, or a
local dealer. These people can review the project with the
estimators and help them arrive at material takeoffs, and
perhaps even suggest a local subcontractor with experience
in installing the tile.

14–17 SHEETS, TILE, AND

SHINGLES FORMULA

Formula 14-2 may be used to determine the number of
sheets, tiles, or shingles required to cover a square (100 sf ) of
roof area for any required lap or seam.

Formula 14-2

Number of Sheets, Tiles, or Shingles per sq.

Where

Nnumber of sheets (tiles or shingles)
Wwidth of sheet (inches)
L length of sheet (inches)
S side lap or seam lap requirement (for some types,
there may be none)
E end lap or seam requirements
To determine the square feet of any given roofing sheet,
tile, or shingles required to cover one square, Formula 14-3
may be used:

Formula 14-3

Square Feet of Material per Square

Where

Asquare feet of material per square

14–18 Liquid Roofing

Liquid roofing materials were developed primarily for free-
form roofs. Composition varies among the manufacturers,
but the application sequences are similar. First, primer is
applied liberally over the entire surface. Then all major
imperfections are caulked, joints taped, and flashing is
applied at all intersecting surfaces. Next, three coats of liquid
roofing are applied; depending on the deck and slope, they
may be either base and finish coats or only the finish coat.
Finish coats are available in a variety of colors. Equipment is
simple, consisting only of rollers, hand tools, brushes, and a
joint-tape dispenser. Labor will be affected primarily by the
shape of the roof, ease of moving about, and so forth. On
some buildings, it is necessary to erect scaffolding to apply
the roofing; in such cases, the cost obviously will increase
accordingly. Before bidding this type of roofing, estimators

A

100 WL

(WS)(LE)

N

(100 ft^2 )(144 in^2 per ft^2 )

(WS)(LE)

should discuss the project with the manufacturer’s represen-

tative so that the latest technical advice may be incorporated

in the bid.

14–19 Flashing

Flashing is used to help keep water from getting under the

roof covering and from entering the building wherever the

roof surface meets a vertical wall. It usually consists of strips

of metal or fabric shaped and bent to a particular form.

Depending on the type of flashing required, it is estimated

by the piece, linear footage with the width noted, or square

feet. Materials commonly used include copper, asphalt, plas-

tic, rubber, composition, and combinations of these materi-

als. Bid the gauge of thickness and width specified.

Expansion joints are estimated by the linear foot, and it may

be necessary that curbs be built up and the joint cover either

prefabricated or job assembled. Particular attention to the

details on the drawings is required so that the installation is

understood.

14–20 Insulation

Insulation included as a part of roofing is of the type that is

installed on top of the deck material. This type of insulation

is rigid and is in a sheet (or panel). Rigid insulation may be

made of urethane, fiberboards, or perlite and is generally

available in lengths of 3 to 12 feet in 1-foot increments and

widths of 12, 16, 24, and 48 inches. Thicknesses of 1/2, 3/4,

1, 1^1 ⁄ 2 ,2,2^1 ⁄ 2 , 3, and 4 inches are available. Insulation is esti-

mated by the square with a waste allowance of 5 percent,

provided there is proper planning and utilization of the var-

ious sizes.

When including the insulation, keep in mind that its

installation will require extra materials, either in the line of

additional sheathing paper, moisture barriers, mopping, or a

combination of these. Also, the specifications often require

two layers of insulation, usually with staggered joints, which

require twice the square footage of insulation (to make up

two layers), an extra mopping of bituminous material, and

extra labor. Estimators must read the specifications carefully

and never bid on a project they do not fully understand.

NOTE:Some roofing manufacturers will not bond the

performance of the roof unless the insulation meets their

specifications. This item should be checked, and if the man-

ufacturer or the representative sees any problem, the archi-

tect/engineer should be notified so that the problem may be

cleared up during the bid period.

14–21 Roofing Trim

Trim—such as gravel stops, fascia, coping, ridge strips, gut-

ters, downspouts, and soffits—is taken off by the linear foot.

All special pieces used in conjunction with the trim (e.g.,

elbows, shoes, ridge ends, cutoffs, corners and brackets) are

estimated by the number of pieces required.