The Design Process - Carpenter's and Builder's Math, Plans, and Specifications - page 235

It is not only desirable, but also necessary that the designer be
familiar with the dimensions of the equipment, furniture, and other
appurtenances found in the home. While it is rarely necessary that
they be accurately detailed, space must be allotted for each one of
them, and space is expensive.
All modern building is governed by codes of some sort. In all
government-financed homes, the government's minimum standards
are strictly enforced, and city codes are often much more restric-
tive. Electrical codes occasionally seem to be unreasonable, but the
building designer must be governed by them. Plumbing is often seri-
ously skimped when no one is watching. Many states have plumbing
codes. However, they do not have the force of law unless augmented
and enforced by local authority. There is a National Plumbing Code ,
and, although it is advisory, it is in line with good practice. It should
be used where there are no local codes. State and local boards of
health may make it quite difficult for the designer of an inadequate
plumbing system if the occasion arises.
For economy, kitchens and bathrooms should be placed back-
to-back. A 3-inch copper soil pipe will fit into a partition of 2 × 4

studs, whereas a 4-inch cast-iron soil pipe won't.
In perhaps most cases, the designer's duty is done when he or she
prepares and delivers the drawings for a job. In some cases, he or
she contracts to inspect the work at stated intervals, to ensure that
the work is satisfactorily done.
The designer should allow for the following thicknesses of walls
in drawings:
Standard wood outside wall — 3

/ 4 -inch plywood or insulating

board sheathing, 3 1

/ 2 -inch studs, 1 / 2 -inch sheetrock inside, 4 1 / 2

inches under the siding
Inside partitions —3 1

/ 2 -inch studs, sheetrock

1

/ 2 inch (both

/ 2 inches
Sound-resistant

sides), 4 1

/ 2 -inch studs
staggered 2 inches, gypsum lath and plaster (both sides) 7 1

staggered-stud partitions —3 1

/ 4

inches
Single-width brick veneer — 3

/ 4 -inch sheathing, 3 1 / 2 -inch studs,

/ 2 inches
Concrete blocks (plastered against the masonry) —8-inch, 8 1

1

/ 2 -inch sheetrock, 9 1

/ 2

inches
Concrete blocks (with furring) —8-inch,

3

/ 4 -inch furring,

1

/ 2 -

inch sheetrock, 9 1

/ 4 inches