Well-written specifications save money and time, from more competitive bidding to clearer scopes, and ensure a quality product/installation.
First, define a specific scope, by product type and application; do not lump related but distinct products or applications together. Some examples: put sloped glazing assemblies in a separate spec instead of in the curtain wall spec; plastic unit skylights and metal-framed skylights in different specs; tubular daylighting devices and skylights in different specs; etc. That said, keep all components of a system or assembly together in one spec. For example, greenhouse windows are an integral component of a greenhouse system and should be in the greenhouse spec rather than in the windows spec; items in a greenhouse space but not integral to the greenhouse system itself, and which can be provided by other trades, such a sinks, trench drains, general non-grow lighting, etc. should be in other spec sections. Doing so delineates logical, separate scopes that can be bid individually (or together), without confusing entanglements.
Once you’ve made your large scope decisions, make sure they (and any smaller items) are clearly delineated in each specification, i.e. what is in that spec and what is in a related spec section. For example, are skylight curbs site-built and in a related general carpentry specification or are they prefabricated and to be provided as part of the skylight specification? If shading, burglar bars, laylites, etc. are to be provided, is the skylight contractor responsible or will other trades be providing them under related specification sections? Will gutters and downspouts for a glass canopy be provided as part of the glass canopy spec or under a related specification?
There are three basic types of specifications: prescriptive, performance, and proprietary. Prescriptive specs enable you to provide specifics of the type of materials and system; they are open to all manufacturers who can provide such a system. Similarly, performance specs allow you to list specific performance standards and/or criteria for a system; they are also open to all manufacturers of systems that meet these. On the other hand, proprietary specs tend to narrowly describe a particular manufacturer’s system and restrict the bidders, often to a single manufacturer. Occasionally, you may truly want a particular product only; many times, proprietary specs are simply chosen as a starting point, and it’s important you edit them to list only the substantive criteria, eliminate irrelevant / unnecessarily-restrictive language, and solicit as many qualified bidders as possible.
Some proprietary spec language to watch out for includes: product approval requirements that are more restrictive than the general 016000 (or similar) section; overly-demanding quality assurance requirements for years in business, similar projects, etc.; unnecessarily exhaustive / restrictive test report requirements under submittals; burdensome and unnecessary submittal requirements (for example, bid time Daylight Autonomy Reports are redundant to the design process and unnecessary for products that comply with the project drawings and specified light transmittance); explicit exclusion of similar but competing products (e.g. “Thermoplastic (e.g. polycarbonate, acrylic) faces are not acceptable.”); construction/performance requirements that are much more stringent than the project’s code requirements (for example, Class A Burning Brand Testing when a Class A roof classification is not required by code); nitpicky numbers for items that are not central to the product’s performance; special “technology” features that are not central to the product’s performance; etc. There are cases where such language may be warranted, but it should be a conscious decision, weighed against the diminishment of competitive bidding.
On a related note, some items that belong in a specification need to strike a balance between cost and utility. Warranties are important for glazed structures; a 2-5 year system warranty will provide protection against defects and abnormal performance and is generally a built-in cost. An extended warranty, 10 years of more, may provide some peace-of-mind (especially for large installations), but is likely to add significant cost – whether or not a bidder will end up with a warranty claim, they must cover the potential cost in their bid. Also, any big problems are most likely to have arisen during the standard warranty period. Testing is another area that provides valuable quality assurance, but can quickly pass from money well spent to money wasted. (See our “Testing” page for details). Mockups (for WSD’s product types) can add significant cost and are rarely warranted.
Finally, be careful that the system you’ve specified is consistent with the associated drawings and details. If you started with a template spec, make sure that all unused options have been eliminated from your final specification.