The Value of Structural Observations on Residential Building Projects

Are they necessary? What is my investment’s return? What is an observation of structure?

A Structural Observation is described as a visual observation to assess that the seismic force-resisting system is created in general accordance with the ASCE construction documents.

Observations of Structures enable Quality Assurance

Minimum quality assurance is required to verify that structures are constructed according to the designer’s intent and in conformity with Code requirements, referenced standards, and the authorized construction documents and specifications. In conjunction with other testing and inspection procedures outlined in the Code, including special inspections by a licensed special inspector, this assures that the structure will perform satisfactorily in the event of an earthquake.

Code sections requiring Structural Observations

The ASCE minimum standards for Quality Assurance include Structural Observations as a component of a quality assurance plan. This document is incorporated by reference into Chapter 35 Referenced Standards of the California Building Code (CBC), which has been enacted into law and is applicable statewide in California.

When are Structural Observations required?

When the severity of the design earthquake ground motion at the site, as determined by the U.S. Geological Society (USGS), is sufficient to assign the structure to Seismic Design Category D, E, or F (high seismic region), and at least one other condition of the structure is met, structural observations are required.

The majority of the state of California fits the description of a high seismic zone, but the other conditions do not typically apply to residential construction (e.g. category of building, height above base greater than 75 ft). When the structure is allocated to Seismic Design Category E (very high seismic zone) and is greater than two stories in height, Structural Observation may be required by these prescriptive Code requirements.

In addition to these specified criteria, each local authority with the jurisdiction (i.e., the local building department or building official) may require Structural Observations under specific conditions. Additionally, any engineer may, at her discretion, mandate Structural Observation.

Where are Structural Observation requirements listed on the Construction Documents?

When necessary, the registered design professional (i.e., EOR) will list the structural observations to be done in addition to the frequency and distribution of structural observation reports. Some cities, including Los Angeles and San Francisco, supply Structural Observation Forms to be included in the construction paperwork (also known as blueprints, plans, and drawings).

If the local authority with jurisdiction does not give a fillable form, the EOR may develop her own table to include in the drawings. Typically located on the cover sheet or the initial few sheets, these are referred to as general notes sheets. This outlines the necessary Structural Observation site visits for the construction project.

Who may perform a Structural Observation?

Observations of structures must be conducted by a California-licensed Civil Engineer or Structural Engineer. The Board of Professional Engineers, Land Surveyors, and Geologists is a resource for additional information regarding license requirements. Since Structural Observation is a visual examination of the constructed structure, it is prudent to employ a local engineer. 

When are Structural Observations performed?

Structural Observations are conducted at crucial stages of construction and prior to the concealment of structural features. These consist of the following:

  •  Foundation work, such as after excavation and rebar has been installed, but before concrete is poured
  •  Wall work, such as after layout of rebar and formwork for concrete walls or after layup of masonry walls after rebar has been installed
  •  Framework, such as after steel is erected and bolts/welds are in place
  •  Floor work, such as after steel decking is in place and welds are in place or after formwork is installed and rebar is in place
  •  Other specific structural elements and their connections as designated by the engineer of record (EOR)

By explicitly identifying these issues, our engineers are able to avoid costly rework or additional work, which adds costs and extends deadlines without the owners’ knowledge. The objective of structural observations is to prevent these unforeseen alterations during construction.

How long does the typical Structural Observation take to perform?

The duration of your engineer’s on-site visit could range from 30 minutes to several hours. This relies on the extent and scale of your building project, as well as the contractor’s construction sequencing strategy. Your contractor may be able to execute the project more effectively by scheduling the various trades (e.g. wood framer, steel erector, concrete pourer, bricklayer, mechanical/electrical/plumbing sub-consultant) to limit the number of individual visits required to undertake a Structural Observation.

How much does a Structural Observation cost?

Due to the fact that the number of different visits for Structural Observation required by the engineer is determined by the quality and expertise of the contractor. Our pricing is a flat rate, but other engineers or large design or consulting organizations typically charge flat fees for either half a day (4 hours) or a full day (8 hours) with no in-between. In this manner, you can avoid paying a set hourly charge of 4 hours if the engineer is only on-site for 30 minutes or 8 hours if they are there for 4-1/2 hours.

What is the deliverable following a Structural Observation?

Following a Structural Observation, the engineer who conducted the observation will list any deficiencies to be corrected on a Structural Observation Report form (which is typically available from each local authority having jurisdiction) and submit this report in writing to the owner and authority having jurisdiction.

Before the authority with jurisdiction authorizes the work, the contractor must now choose the proper line of action to rectify the deficiency. The engineer is not prescribing a specific plan of action for the contractor to take to repair the problem; she is merely stating the deficiency. Typically, the process of fixing the shortcoming is handled through the usual construction contract administration process, in which the contractor submits a request for information (RFI) for either direction or approval of an alternate means or technique of construction.

What are some typical flaws that a structural engineer may identify on the Structural Observation Report Form for correction?

Some specific forms of defects that may result from faults in reading the construction plans or improperly constructing the home include the following:

  •  Steel column anchor bolt to be set in concrete oriented in the wrong direction if the base plate anchor bolt pattern is not set in a square pattern
  •  Lack of seismic details included in rebar layout (if shop drawings are submitted for EOR review prior to installation via our Construction Support
  •  Services page, this can be identified even before the Structural Observation is performed)
  •  Installation of steel deck on steel beams and columns with a lack of proper welds or fasteners
  •  Incomplete connections between the floor elements and the wall elements.
  •  Missing straps and holdout hardware that resist overturning forces due to earthquake loading

In the event that issues are not recognized in a timely manner, it may be more expensive to rectify any shortcomings after the fact. If, for instance, the concrete is poured before a Structural Observation is conducted to observe the rebar layout and detailing, then taking out the concrete to install the rebar according to the plans will add needless time and cost to the project. The purpose of Structural Observation is to uncover these flaws before they are concealed by other structural elements or finishes.

In terms of time, construction costs, and modification orders, what are the savings?

Implementing Structural Observations as part of the overall quality assurance plan for the project guarantees that the structure is constructed according to the original designer’s intent. Even if you pick a respected contractor, there is a possibility that he will engage subcontractors who are not as qualified or who have difficulties understanding and interpreting construction designs.

Construction schedules may sometimes cause contractors to hustle and cut corners. This can result in construction defects that must be rectified by the contractor in order to ensure that the building will perform well when subjected to Code-level earthquake pressures. Observations of the structure are conducted to discover and fix these defects prior to their concealment by interior finishes, which render observation impossible without destructive destruction.

In exchange for a nominal fixed price for each Structural Observation, you receive the knowledge and experience of a California-licensed engineer who has worked on similar projects in the past. By identifying and rectifying any observed flaws, you save time overall throughout construction by avoiding the need to redo work. Having an engineer verify that the contractor did not build it appropriately may help you avoid change orders on your project, in which the contractor may claim recompense for his substandard work. This could aid in preventing your contractor from issuing these dreaded modification orders.

Why is it generally suggested to employ an engineer to do Structural Observation even when it is not mandated by the applicable code or local authority?

We hope this post makes it clear that you should hire an engineer to complete the essential Structural Observations for your project. Even if the structure does not possess the characteristics of a building where Structural Observation is required by the Code or the local authority having jurisdiction does not require Structural Observation to be performed, the design professional responsible for the design of the seismic force-resisting system is ultimately accountable for the quality assurance plan applicable to that system. In addition to other Code-required and city-mandated inspections, this is a way of examining the contractor’s work.

Schedule a Structural Observation today

Please contact us immediately if you would like an estimate for Structural Observation for your project. Please offer at least two business days’ notice when a structural inspection is required for your project. Your contractor may submit his construction timeline, but this may be subject to change owing to circumstances beyond his control (such as inclement weather). Therefore you may wish for him to convey this information to the engineer instead.

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