242 Chapter 10
10.3 TYPES OF SPECIFICATIONS.
One of the first things that a specifier has to decide upon when preparing a specification document is the
format or method to be used to communicate the desired intent to the contractor. There are essentially
two broad categories of specifications, closed or open, and most items can be specified by either
method. Within these two broad categories, there are basically four generic types of specifications: pro-
priety specifications, description specifications, performance specifications, and reference-standards
specifications. The type chosen depends on several factors (Figure 10.1). These are discussed below.
Closed Specification.
Closed (also called prescriptive or restrictive) specification is one that limits acceptable products to one
or a few brand-identified types or models and prohibits substitutions. This type of specification is some-
times used where specifiers feel more comfortable resorting to a specific proprietary product with which
they are familiar and which will meet the specific criteria of the project. However, it should be noted that
this procedure (particularly when only one product is named) is not competitive and rarely attracts the
most favorable price for the owner. Also, while a closed specification is common in private construction
work, most public projects are required by law to be bid under open specifications.
The closed proprietary specification method is the easiest form to write but the most restrictive, in
that it names a specific manufacturer’s product. It generally establishes a narrower definition of accept-
able quality than do performance or reference-standard methods, and gives the designer/space planner
complete control over what is installed. The specification can also be written as an open proprietary sec-
tion, in which multiple manufacturers or products are named or alternatives solicited. This would in-
crease the potential competition and encourage a lower installation price from vendors. In some cases,
a multiple choice may not be appropriate, as, for example, where a specific brick is required for repairs
to an existing brick facade. When the specification does not allow for any substitution of materials, it is
known as a base bid proprietary specification.
Open Specification.
Also called performance or nonrestrictive, this type of specification gives the contractor some choice in
how to achieve the desired results. Proprietary specifications may also be used as open specifications
but with the addition of the “or equal” clause, which allows the contractor to consider other products for
bid if they are shown to be equal in performance and specifications.
Due to the ambiguity surrounding this clause and the disagreements it often perpetuates, specifiers
generally shy away from incorporating it into proprietary specifications.
A second method of open specification that is gaining popularity is descriptive specification.
This type of specification describes in detail the requirements for the material or product and the
workmanship required for its fabrication and installation without providing a trade name. This type of
specification is often stipulated by some government agencies to allow the maximum competition among
product manufacturers. Descriptive specifications are also more difficult to write than proprietary ones
because the specifier must include all the product’s relevant characteristics in the specification.
A third type of specification that is often used is the reference standard. This standard simply de-
scribes a material, product, or process referencing a recognized industry standard or test method as the
basis for the specification and is often used to specify generic materials such as portland cement and