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5 Types of Construction Specifications Explained

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are one of the most important elements in a construction document set. Without them, it would be nearly impossible to complete any construction project.

There are 5 main types of construction specifications: 

  • Performance specifications
  • Prescriptive specifications
  • Proprietary specifications
  • General specifications
  • Detailed specifications
Keep reading for in-depth explanations of each type of specification, their importance, and how to write construction specifications for your projects.

Types of Construction Specifications

Here is a rundown of the aforementioned types of specifications in construction:

1. Performance Specifications

Performance specifications, also known as performance criteria or , describe the final results expected from a construction project. They are commonly used when the result is subjective, such as performance or aesthetic values. In this case, performance specifications may be necessary to define things like acoustical design values and requirements for finishes. Performance specs can also be used for objective standards that need to be met by a construction project, such as weathertight window assemblies or fire rating levels for exterior cladding materials. Performance specifications don’t explain how something should happen; instead, they describe the end goal of a building’s components once the project has been completed. Performance specifications are often included with prescriptive and detailed specifications to help show how much of an improvement over previous versions of these types of documents will occur with the new construction project. Example of performance specification from the design phase:

Fenestration assemblies shall be designed to provide at least an {insert fire rating} hours per side for each story per and , or {insert fire rating} hours per floor for a building.

Request For Proposal (RFP) documents tend to use performance specifications more frequently than other types of specs. This is because many potential bidders on construction projects might have different ways of accomplishing the same goal. If left unaddressed, this could lead to confusion among interested parties unfamiliar with the project and its overall goals and objectives. Performance specifications can also be used as a guide for assessments performed by building consultants or maintenance professionals to determine if the design of a building meets the owner’s expectations or needs.

2. Prescriptive Specifications

Prescriptive specifications describe required materials (including product options) for installation methods and activities to complete different aspects of a construction project. The idea here is that all products specified within this type of specification must be used for the project to meet its performance requirements. The main advantage of a prescriptive specification over a performance specification is that it allows contractors, material manufacturers, and product consultants to use their own products to comply with all design objectives for the project without having to contact the building owner or contractor for approval each time something needs changing. In this way, prescriptive specifications are very similar to proprietary construction documents. Notably, both documents contain exact details about what materials should be used and how they should be installed – down to the manufacturer level in many cases. Example of a prescriptive specification from the design phase:

Walls shall be constructed using Type {insert wall type}, and shall be sheathed with {insert brand name} wood boards, covered with {insert brand name} plywood paneling.

All assemblies shall have a minimum R-value of {insert thermal performance value here}.

Walls will be covered in layers that make up an assembly consistent with fire stops covering all gaps between walls and other building components per installation plans.

Notice from this example that the prescriptive spec only requires one particular material option to construct the wall – but it doesn’t necessarily say which product is needed. This gives contractors and material suppliers more flexibility when they’re working on the project. Still, it also means that the building owner will have to stay on top of any changes or issues with the materials used. Nearly all specifications can be considered prescriptive since they’re meant to tell architects and contractors what products should be used to construct a building. However, there are still some instances where general and detailed construction documents may take this approach.

3. Proprietary Specifications

Proprietary specifications are very similar to prescriptive construction documents—except for the fact that they’re written with one particular product in mind. This means builders must use those specific materials when constructing the project. A proprietary specification is used by architects and contractors whenever a specific product is required due to its relationship with the owner’s company or something else associated with the building (like high-end luxury finishes in a hotel, for instance). Example of a proprietary specification from the design phase:

Exterior cladding shall consist of {insert brand name} ’s fiber cement panels assembled using their proprietary system, which will also include an integrated drainage layer per their recommendations.  

Wall systems will be pre-framed at the site and shipped to the site, ready for installation. The most significant advantages of a proprietary specification include:
  • Freedom from the confusion that may arise by using similar materials with different brand names.
  • The peace of mind that comes from working with one company to meet all design objectives for the project.

4. General Specifications

Commonly used in commercial and residential work, this type of construction specification is called a general spec. It contains product information but doesn’t specify which manufacturer must be used. In some respects, this can serve as a middle ground between prescriptive specifications and performance-based documents. However, this document is typically not appropriate for complex projects where unique features are required. Example of a general specification from the design phase:

Exterior walls will include a 4-inch (10.16 cm) layer of insulation installed before the fiber cement panel cladding.

All joints between panels shall be caulked for water-tightness.

A general specification covers various options – including both materials (like the recommended products above) and details on installation processes like how many layers of paint should be applied throughout construction. A general spec may also contain information about what quality testing needs to occur before the process is complete. This ensures that it meets various standards like LEED certification or other building codes.  

5. Detailed Specifications

A detailed spec is slightly different from a general one because it covers virtually every aspect of construction in precise terms. This includes everything down to the number of screws used to fasten materials together. This type of construction specification is typically used when owners have little or no experience working on large-scale projects and need more guidance. A case in point is when they’re responsible for overseeing these tasks themselves. One typical example of this approach is when homeowners purchase their first home and decide to renovate without hiring a contractor. Generally, detailed specifications can be either standard or special. Here is an overview of each:
  • Standard specifications: These are the most common types and cover things like flooring materials and steel thickness requirements for beams and columns. As their name suggests, they are standard and can be used in construction projects in the same category.
  • Special specifications: Special specs are typically used in more complicated cases where unique details might be required (like installing a specific brand of windows or doors). They’re often the most detailed type of construction specification. Key stakeholders must approve them before they can become part of a standard set.
When you’re choosing which to use for your project, it’s important to note that both detailed and general specs are necessary to protect the interests of homeowners and contractors alike.

Importance of Construction Specifications

Catering to specific requirements is extremely important in the construction industry. Not only does it save time, but it also ensures top quality in all products used during construction. Without these guidelines, numerous problems would likely arise—from inadequate materials resulting in poor workmanship or installation issues with various building systems, jeopardizing public safety. That said, here are three key points that demonstrate the essence of construction specifications:

They Serve as a Blueprint

Construction documents serve as a blueprint for builders during construction preparations. They outline the process necessary to install various building elements (walls, roofs, electrical systems) while also detailing what’s expected from the end product. This means everything from how it should look upon completion to its ability to withstand unfavorable weather conditions over time. These are crucial aspects, especially when building in disaster-prone areas. Construction specifications also protect the homeowner by setting a level playing field for contractors.

They Help Control Costs

These guidelines set standards and expectations so that all parties can see eye-to-eye on what’s being installed. They also set when specific items will be installed, and most importantly, how long it will take to get the job done. This means no costly delays or additional costs at any point in the process. This is often great news for homeowners who need to stay within budget limitations while completing their projects on time.

They Promote Quality

This point is pretty straightforward because it’s the whole reason that construction specs exist in the first place. Notably, the contractor can assure the level of quality and workmanship to some degree with these documents. It’s a no-brainer that a poor installation can lead to numerous problems down the road or, in extreme cases, even endanger your family’s safety. Therefore, it’s essential to understand that proper documentation before any work is performed will ensure safety in the long term. This video by the Federal Highway Administration summarizes the types and uses of construction specifications in under ten minutes:

How To Write Construction Specifications for a Contract Document

Writing detailed specifications is an interesting process because it involves much creativity and careful thought during the development stage. As you can imagine, these documents are instrumental in ensuring all parties involved understand how items should be fabricated or installed onto a building. So they have to be very thorough and detailed to communicate this information effectively. For those with little to no experience writing detailed specifications, the following steps summarize how this process should be carried out:

1. Develop Your Specifications

This is the point at which you’ll identify and note your project’s requirements, including the expertise needed for each activity. For example, suppose there are electrical requirements for that particular phase or room in a building plan. In that case, this would be when to determine how those specifications will be met. In such a case, you may want an electrician involved with these decisions as well so they can provide their expertise on what type of wiring should go where and clarify any questions related specifically to wires themselves.

2. Prepare a Writing Schedule

You’ll typically want enough time to write these documents in such a way that they’re easily understood. Because of that, scheduling them for completion at least 12 weeks before construction is expected to begin is a good rule of thumb.

3. Create your Draft

This step involves taking all of the information you have so far to create what is known as a “working draft.” It would help to review the draft for errors or additional details that need to be included. Doing so ensures everything is phrased and written in a manner that is easy to read. Make sure your drafts are error-free by having someone else review them before creating the final draft.

4. Ask For Feedback

Another crucial step is to have your drafts reviewed by the contractor and engineer. This should be done before completing the final draft of the construction specifications documents. Their feedback will help you correct any mistakes or unclear clauses that may exist in your present copies. The key takeaway, in this case, is to ensure your working drafts are clear, concise, and complete before getting them finalized.

Remember: It is essential to be very thorough when creating construction specifications for a contractor or owner. This will ensure any potential issues can be resolved in the planning stage instead of during the actual work.

For in-depth guidelines on how to write construction specifications, a good resourse is the book (available on Amazon.com). The authors offer detailed, practical, and easy-to-understand steps on writing these documents, making this book a worthwhile addition to your construction specification arsenal.

Sources

By Giovanni Valle

Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.

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