roof and pavement consultants

The Pitfalls of “Corporate Roofing Design Standards”

by Kent Mattison, P.E.

Many businesses and institutions have developed generic “Master Roof Specifications” or “Roofing Design Standards” in order to develop design consistency for future roofing projects. Benchmark has often been asked to help develop these standards. This may sound counterintuitive but, in most cases, we no longer recommend our clients use such standards.

Why is that?

Roofing Design Standards definitely can be a good starting point. But they should only be used as a starting point. And that’s the problem. Too often they are used in the wrong way. Design Standards are not only used in the hopes of developing consistency, but also to avoid the time, effort and cost of developing a site-specific roof design for each individual roofing project, which we recommend. But the risks are high.

Here are some of the pitfalls we have run into when developing generic Roofing Design Standards or Master Roof Specifications for others:

First of all, how basic or detailed is this Corporate Design Standard going to be?
The time and cost to develop such a document can vary dramatically, depending on how much detailed information is included.

If it’s too elementary, it provides little guidance and is almost useless.

But developing a very thorough document, with several systems and products, can be very time consuming, expensive, and frustrating.

Besides the waterproofing membrane, the “roof system” may include adhesives, fasteners, ballast, pavers, insulation, cover boards, base sheets, vapor retarders, air retarders, etc. And, roof-related items such as skylights, sheet metal, rough carpentry, drains, sealants, roof hatches, masonry repairs, deck replacement, etc. are often included in the roofing project.

Benchmark first developed its own Master Specification over 20 years ago. Approximately 25 generic roof systems and over 60 individual product sections are now part of this Master Specification. Our technical committee has spent several thousand hours constantly revising/updating it as code, insurance, and manufacturer requirements change and new methods and products become available. The “Master Spec” is our ‘starting point.’ It is amended and revised significantly for each individual project to meet the unique site specific design requirements.

How are the Corporate Design Standards going to be used?
The document, as is, should never be handed to a contractor to bid a specific roofing project. When a Design Standard is provided, it should always be modified to meet the parameters of each individual project, In our experience, this doesn’t usually happen. Therefore, contractors bidding the project are left trying to determine how they can be low bid, and the owner is often left comparing bids for completely different roof systems without any concern for the specific needs of the building and building operations. Change orders can become a common occurrence throughout the project. Without site-specific bid documents encompassing existing conditions, design criteria, roofing components, code and insurance requirements, you will seldom get comparable, accurate and meaningful bids.

If the Corporate Design Standards are modified to meet site-specific requirements, who does that?
The person who developed the Design Standards and the one revising it to meet the site-specific needs of the roofing project are rarely the same person. When the Master Specification is developed by one design professional and is modified by another design professional, the two designers often have different design philosophies and approaches. In addition, though both may have design input, they seldom communicate with one another as a team. Therefore, continuity and consistency of the design is inadequate and much of the design effort is duplicated. This lack of consistency and added duplication increases cost and dilutes the quality of the specification. When questions do arise, each designer may have a different response based on their role in the design.

What happens to “Master Specifications” when regulations, codes, products, and installation methods change?
These changes occur frequently. When one seemingly small item is changed, it often causes a change reaction – requiring updating other related specification sections. These specification changes are seldom done for any number of reasons: added cost, perceived unimportance of the update, being unaware of the change, or no one having the responsibility for keeping the document current. An outdated specification may therefore not meet code, warranty, and/or insurance requirements. We often see products being specified that no longer exist.

Which products should go into a Corporate Design Standard?
Each product manufacturer may have numerous products that can be used in many ways. It’s virtually impossible to provide all the scenarios available in a Master Specification without it being cost prohibitive to our client. For example, modified bitumen manufacturers may have anywhere from 20 to 100 assorted membrane products that can be used in different combinations on different deck types. Their various sheets can be attached using cold applied adhesive, hot asphalt, torches, self-adhering or combinations thereof. Providing a master specification with all these possibilities becomes very difficult for the designer of record to sort through and costly for the client. The same is true for any number of roofing components.

Because of these challenges most Corporate Roofing Design Standards become obsolete in a short period of time. Use of a roofing design standard requires continuous maintenance and updates for it to be an appropriate and cost-effective design tool.

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