Total Building Costs By Percentages. Having carefully estimated the costs of one or two of the large items in a building, such as lumber or millwork or labor, the total cost of a building may be approximated with a fair degree of accuracy by a general contractor by means of the following table of percentages. Foundations or any other parts of a building which may be unusual should be excluded and figured separately in detail. In any event, before a building is finally completed the contractor will have to settle with each sub-contractor upon the basis of detailed cost estimates. Where time is available, the contractor as a rule secures bids from the various sub-contractors, such as the plumber, the lather, the mason, etc., combining these and adding his commission of 10% for oversight, and an additional 10% for incidentals or contingencies.

Costs By Percentages

Items

Frame Building

Brick Dwelling

Excavation, brick and cut stone......................

16%

36%.

Plastering and materials, including lathing.............

8

6

Millwork including glass and glazing..................

21

20

Lumber...........................................

19

12

Carpentry labor ...........

18

10

Hardware.........................................

3

3

Tinwork and galvanized iron.........................

2

4

Plumbing and gas fitting and materials................

7

3

Painting and materials..............................

5

5

Heating (not included)

Total.........................................

100%

100%

Example:

A lumber bill for a given frame house is found to "figure" $500, determine the approximate cost of the various sub-contracts, and for the house as a whole.

Solution:

$500 = 19% of the total cost.

Total cost = $2632 (exclusive of heating).

Excavation, brick and cement work = 16% of $2632

=

$421.12

Plastering = 8% of $2632....................................

=

210.56

Millwork and glazing = 21% of $2632........................

=

552.72

Carpentry labor = 18% of $2632.............................

.=

473.76

Hardware=3% of $2632..................................

=

92.12

Tinwork = 2% of $2632...................................

=

65.80

Plumbing = 7% of $2632....................................

SB

184.24

Painting = 5% of $2632......................................

=

131.60

Lumber......................

=

500.00

$2631.92

To this must be added heating, electric wiring, electric and gas fixtures, window shades, cement walks, sewerage, grading, decoration of walls, architect's fee and contractor's commission.

For furnace heat, add 6 to 7%; for steam, add 8 to 10%; for hot water, add 10 to 12% additional.

For electric wiring, add 1%- For fixtures, electric and gas, add 2 to 3%.

To this total add 10% for incidentals and contingencies; add 10% for contractor's charge. Above this amount add 6% for architect's fee, to get the cost to the owner.

Such a method of estimating should not be mistaken for anything but fairly safe approximation where normal conditions exist.