Local Building Designers Help Truss Sales

Originally published by the following source: SBC MagazineJune 24, 2019
by Jess Lohse with contributions from SBCA Staff


Editor’s Note: The following article is part of SBCA’s Construction Industry Workflow Initiative, which is exploring how the construction industry currently functions and the role component manufacturers play within that structure. Your feedback is encouraged to help us complete this project, email workflow@sbcindustry.com to provide your input.

A vast majority of single-family homes built each year in the U.S. are designed by someone other than a licensed architect. Some estimates have the number of homes designed by architects as low as one or two percent. This is due to a typical law exempting residential structures from the requirement of using a Registered Design Professional. This state of Washington summary is typical.

The International Residential Code (IRC), as outlined in a previous article, allows many options for single-family design outside of the umbrella of licensed professionals through a “prescriptive” approach. This process is undertaken by a Residential Building Designer, referred to in ANSI/TPI 1 Chapter 2 as a building designer, who focuses on many of the same details as an architect, but works from a different perspective. 

One significant difference is that building designers have to be concerned about the price point of the finished project, either through establishing and remaining within a budget for a custom designed project, or maintaining the affordability of a newly constructed home in a build–to-sell sales model. In a custom design project, one of the first questions a designer will ask is about the budget. If a budget has not yet been determined, the client will often be directed to speak with a lender to know how much house they can afford given their current circumstances. Once a budget has been established, a designer will walk through a series of questions with the client to understand their intended use and purpose of the home, and only then perform many of the steps an architect performs during their programing phase

Like an architect, a residential building designer is concerned with the look and feel of a home. Building designers will also look at certain structural elements, ensuring bearing walls stack level-to-level as an example, and will often include header sizes from conventional framing tables in the IRC

However, building designers typically leave a majority of the structural design for a single-family home to others. Structural roof design is often out-sourced to a component manufacturer (CM) and their delegated engineer, in instances where roof trusses are used, providing individual sealed roof truss design that make up the roof system solution. If roof trusses are not used, framers will refer to span charts within the IRC to stick frame roof and ceiling joist members. 

Floor systems are typically outsourced to whomever is providing the structural materials. I-joist floor systems are designed by technicians employed by a building material supplier. Floor truss systems are designed by a CM and are one of the few options for an engineered/sealed floor member. In instances where dimensional 2x10 or 2x12 joists are utilized, framers are left to essentially frame the floor system based on their interpretation of span charts within the IRC code. Foundations are designed either by the building designer using solutions found typical to the jurisdiction where the home is located, the IRC, or can be outsourced to an engineering firm if required by that jurisdiction. 

Building designers will typically spend a majority of their time focused on the main floor of the structure, estimated up to 85 percent of their time specifically on the living room, kitchen, and master bathroom. Beyond the main floor plan, designers spend a significant amount of time detailing the elevation plans, allowing clients to better visualize the finished product.  With the look and feel established, building designers will then prepare additional design documents according to the requirements of local building departments and code. These documents may include a site plan, foundation plan, electrical plan and/or mechanical plan.

Notably, often left out of the plan documents are structural designs such as a floor joist layout, roof plan and any post and beam specifications.  These items can be included in the plan set, but vary widely by individual building designer and depend on what they are contracted to provide. Clients may elect to choose a vague plan approach in an effort to lessen upfront costs and push decisions downstream to other professionals to figure out the nuances of the structure. This work the falls to the framer, CM or material supplier(s). The unfortunate drawback to this approach is often those professionals do not receive direct compensation for that work. This lack of standard offering in building design results in a wide range of plan set cost and compensation for the building designer. 

Because of this, some building designers have seized upon the opportunity to expand upon their services, and will walk through each of the product offerings in the structure, ensuring apples-to-apples comparisons when the project is bid out. Examples of these specifications include structural solutions, common finishes such as door styles, cabinets and counters, and even lighting options. This latter approach allows homeowners the opportunity to fairly evaluate comparable estimates when looking to build a home, adding transparency and uniformity to the process, as well as ensuring the other professionals involved in the building’s construction are not left doing work without compensation.

Building designers fill a very important role in the construction process and are able to provide a service at a competitive price point for their client. However, while traditionally more cost-effective than construction documents provided by an architect, plans developed by building designers vary greatly in approach, uniformity and detail with each designer requiring various professionals downstream to interpret different aspects of their plans. Professionals who read building plans must be adept to many different styles and take on significant risk interpreting those plans when compiling and submitting estimates for various stages of construction. 

Thank you to Tanya Cromwell of Idaho Home Design for providing background information for this article.

Related Articles:

The Development Life Cycle for a Building
The Structural Design Process of a Building