According to the American Institute of Architects (AIA) Document A201-2007, the Contract Documents for a construction project consist of “the Agreement, Conditions of the Contract, Drawing, Specifications, Addenda…”, as well as other miscellaneous documents associated with the contract between the project Owner and the Contractor hired to complete the work. Construction specifications, as noted, become a part of the legal documents of the agreement and form a cornerstone of the project design. In fact, in most cases, the construction specifications override the project drawings in the event of conflicting information.
The purpose of construction specifications is to delineate the requirements regarding the materials, products, installation procedures and quality aspects involved with execution of the work and fulfillment of the contract. There are three main types of construction specifications: performance, prescriptive and proprietary, which are described below.
A performance specification is a document that specifies the operational requirements of a component or installation. Simply put, a performance specification tells the contractor what the final installed product must be capable of doing. The contractor is not instructed as to how to accomplish the task of meeting the performance specification requirements - only as to how the component must function after installation. For example, a performance specification may be used in the construction of an industrial pumping system. The specification would provide a required pumping rate (say 500 gallons per minute), a required pressure (20 psi) and the difference in height between the pump and the final destination (+40 feet). The specification will also state that the liquid to be pumped will be at a temperature of 140°F and is corrosive (pH of 3). It is up to the contractor to provide pumping equipment that meets or exceeds the requirements stated in the specification. In many cases the contractor will also be required to test equipment to make sure that is operating properly, and will provide operations manuals.
The general concept behind the performance specification is for the architect or engineer to describe what they need, and the contractor to determine the best way to get there. The performance specification focuses on the outcome and shifts the selection of materials and methods, as well as a portion of the design work, onto the shoulders of the contractor. This approach can provide incentives for innovation and flexibility in the construction approach, but also reduces the amount of control that the architect or engineer has over the project./p>
Prescriptive specifications convey the requirements of a project through a detailed explanation of the materials that the contractor must use, and the means of installing those materials. This type of specification will typically be formatted in a manner similar to the following sections:
- General: This section will typically contain references to national/international standards, design requirements, a list of required submittals from the contractor to the architect/engineer, quality control requirements and product handling requirements.
- Products: This section will describe, in detail, the various products required for the task covered by the specification along with the individual structural and performance requirements of each product.
- Execution: This section will explain how to prepare the materials and conduct the installation, including the testing requirements to be followed.
Prescriptive specifications shift more of the project design control onto the shoulders of the architect or engineer and away from the contractor by establishing a set of rules that is to be followed for each project component. This type of specification provides more certainty regarding the final product composition than the performance specification, and is very frequently used for highly complex portions of a project.
Proprietary specifications are those that require the use of a single approved product type for any particular installation. Proprietary specifications are often used in cases where there is existing equipment or installations already on site. In these cases the owner may want to maintain consistency of materials or possibly simply prefers a specific type of product. Also, in highly complex installations where there is only one specific piece of equipment that will accomplish a specified task, a proprietary specification is required.
Architects and engineers typically try to avoid utilizing proprietary specifications except when absolutely necessary, and will usually allow the contractor to select from a list of approved suppliers. Requiring the use of one specific product type can lead to the perception of favoritism towards a certain manufacturer and may eliminate competition during the bid phase, which may increase the project cost.
Construction Specification Standards
Construction specifications used in the United States typically conform to the guidelines of the Construction Specifications Institute (CSI), who have created a specifications index entitled MasterFormat. The MasterFormat index groups specification sections into easily identifiable disciplines using a six-digit system with digits in groups of two, such as: 01 24 30.
The first two digits denote the primary section (of which there are 48 sections). For example, all the items regarding concrete start with the digits 03.
The second two digits identify the main headings and subheadings. In this case, we look at main headings Concrete Reinforcing (03 20 00) and Cast-in-Place Concrete (03 30 00) which can be broken down into Reinforcement Bars (03 21 00) and Structural Concrete (03 31 00).
The breakdown continues further with the final two digits, for example: Plain Steel Reinforcement Bars (03 21 11) and Heavyweight Structural Concrete (03 31 13).
Use of MasterFormat allows professional and construction personnel alike the ability to use a common system to reference and group materials and equipment when utilizing specifications, pay applications, estimating programs, etc. For a list of sections, refer to our MasterFormat Specification Divisions article.
In addition, CSI also maintains UniFormat Specifications, which are used for the early phases of a project. UniFormat allows construction teams to begin investigating project schedules and costs without the detail of MasterFormat.