Understanding Prescriptive Specifications in Construction

Every stakeholder in a construction project relies on specifications — from general contractors and suppliers to consultants and buyers. For a range of reasons, construction specifications vary in their level of detail, but their overall purpose is to clearly provide information that drawings cannot depict.

Like most construction specs, prescriptive specifications are written by the architect or engineer. They are akin to a doctor’s prescription detailing what to take, when and how. In the context of construction, this “prescription” explains what materials and products to buy, the project stage to use them in, and how installation should proceed.

This article examines the details of prescriptive specs, examples of how they work and their benefits to a project.

Construction Specs: A Brief Overview

Construction specifications fall into three main categories: performance, proprietary and prescriptive.

• Performance: Performance specifications zero in on the outcome of an installation or build.
• Proprietary: Proprietary specifications, mostly used in the private sector, cite product brands or manufacturers.
• Prescriptive: Prescriptive specifications reference construction details like the building codes, products, materials and procedures to achieve a build.

Closed vs Open Specifications

Construction specifications are further classified as "open" or "closed." When specifications are open, contractors are free to select their own suppliers, materials and products based on standards set in the specification document. Performance specifications are open by nature. 

Closed specifications give contractors less leeway in that they list materials and products. For this reason, proprietary and prescriptive specifications are considered closed.

What goes into prescriptive specifications?

Prescriptive specifications are used from the bid package onwards and can drive productivity and efficiency by streamlining workflows.

Prescriptive specs cover three key elements.

1. General Provisions

• Regulatory Standards

  This section outlines all relevant laws, regulations, and industry standards that must be adhered to during the project. It includes federal, state, and local regulations, as well as any applicable building codes and zoning requirements.

• Building Codes

  Detailed specifications from relevant building codes, such as the International Building Code (IBC), are outlined in this section. These make sure that the construction adheres to safety and structural requirements.

• Design Requirements

  This section encompasses the specific design criteria and performance expectations for the project. It may include architectural drawings, engineering calculations and other technical specifications that guide the construction process.

• Submittal Package

  This is a detailed list of documents, samples and technical data that must be submitted for approval before construction begins. This ensures that all products and materials meet the project's requirements.

• Product & Material Handling

  Specific instructions on how to handle, store and transport construction materials to prevent damage and guarantee proper installation should be included.

• Quality Control

  Include procedures and protocols for inspecting and testing materials and workmanship so they meet the specified quality standards.

2. Product Requirements

• Type of Products & Materials

  Include a comprehensive list of approved products and materials that can be used in the construction. This section may also include alternative products that can be used with prior approval.

• Performance Standards

  This section outlines the expected performance levels of the products and materials, including their durability, strength and resistance to various environmental factors.

• Structural Specs

  Note the detailed specifications for structural components, such as beams, columns and foundations, to ensure the building's stability and safety.

• Dimensions & Sizes

  Include precise measurements and tolerances for all products and materials for proper fit and function.

3. Execution Procedures

• Preparation Processes

  Step-by-step instructions on how to prepare the construction site and materials for installation. This may include excavation, grading, and surface preparation

• Installation Recommendations

  Detailed guidelines on how to install the products and materials correctly, including best practices and potential pitfalls to avoid

• Quality Assurance Measures

  Procedures for monitoring and inspecting the installation process to ensure it complies with the project's specifications and quality standards

• Efficacy Testing

  Methods for testing the performance and functionality of the installed systems to ensure they meet the project's requirements — this may include pressure testing, load testing, and other forms of performance evaluation

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Examples of Prescriptive Specifications

Unlike performance specifications with a primary focus on the end result, prescriptive specifications lay out a roadmap for the construction process. Below are three examples of prescriptive specifications.

The Benefits of Prescriptive Specifications

Prescriptive specifications are incredibly useful due to their high level of detail and specificity, outlining exactly what materials and products must be used, as well as the installation and construction methods to be followed. This detailed approach offers advantages in risk mitigation, collaboration, budget management and accountability. 

Risk Mitigation

One advantage of prescriptive specification is that is contributes to mitigating risk and loss, particularly on complex building projects. The accuracy it provides contractors and suppliers tends to reduce delays and cost overruns because it minimizes guesswork. This ensures that quality and safety meet certain standards, causing fewer time-consuming and costly disputes.

Collaboration

Having everything spelled out clearly contributes to a more successful collaboration among stakeholders because there is a shared reference for communication. This leads to stronger working relationships and higher productivity.

Budget Management

Since prescriptive specification provides a list of materials and methods, the owner is assured that installations will match its requirements. On most types of projects, this increases confidence to hire the contractor of their choice at a negotiated rate, which can greatly improve spending visibility. It also makes approaches like value engineering more viable and effective for optimizing resource allocation.

Accountability

By providing contractors detailed instructions, prescriptive specification explicitly states where liability lies, thus making accountability much easier to determine. It can also be an invaluable asset for avoiding recourse to the Spearin Doctrine, for example.

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