Specification forms a critical component of the construction process as it provides a clear and concise set of guidelines for all parties involved.
While there are different types of specification in construction, used at different stages of a project’s development, the overall purpose of specifications is to ensure that the project is built to the required standards and meets the expectations of the client. By ensuring that everyone is on the same page, the chances of errors, delays and misunderstandings are greatly reduced, leading to a successful construction project.
Types of Specification in Construction
There are three common types of specification in construction, used by architects, engineers and contractors to specify the materials, products and construction methods used in a project. These are descriptive/performance specifications, prescriptive specifications and proprietary specifications.
It is worth noting that specs may change during the design and build process; while you may start out with a descriptive specification, this can soon become quite specific and end up as a proprietary specification.
Performance/Descriptive Specifications
Performance specifications specify the desired performance criteria of the products or materials used in a construction project. Instead of prescribing the specific product or material to be used, they define the desired outcome and leave it up to the contractor or supplier to choose the product or material that meets those specifications. Performance specifications can provide more flexibility in the selection of products; while this could lead to the selection of a less expensive, less reliable product, it can also encourage innovation in product design and construction techniques.
Example: Cladding system
Fire Performance
- Standard: AS 1530.3
- Spread of flame index: 0
Prescriptive Specifications
Prescriptive specifications are one of the most used types of specification in construction. They provide a more detailed description of the products or materials to be used in a construction project, including their dimensions, quality, installation requirements and performance criteria. While being more specific appears to reduce the flexibility in choosing a product or material, prescriptive specifications still allow contractors, manufacturers and consultants to use their products that comply with the design objectives for the project.
Example: Doorset system
Products
- Supplier: Alspec
- Hardware: Wide lock stiles
- Glazing: 18mm double
Proprietary Specifications
Finally, a proprietary specification looks at specific products made by specific manufacturers i.e. they are written with one product in mind. This type of specification gives architects and building designers confidence and certainty in the final project design as there are no questions around the exact quality, finish, performance and durability of the product choice.
Example: Cladding system
Products
- Supplier: Lysaght
- Ref: Custom orb
- BMT: 0.42
What to Consider When it Comes to Developing a Specification
Specification information describes in words things that cannot be visualised in drawings. The content can include site requirements, contract information, client requests, performance criteria, the quality of products, how the work is to be completed and tested, and maintenance of the building in use. With all this content in mind, project specifications also need to be accurate, comprehensive and up to date.
An architect may work with a specification consultancy throughout the design and construction process to ensure that the specifications follow applicable building codes and regulations. The consultancy can also assist in researching, evaluating and selecting the appropriate building products and materials to ensure that the project is completed to the required standard.
Software developments have greatly improved the process of submitting specifications. Instead of printing and sharing 200+ pages of work, spec documents can now be easily navigated online and read in conjunction with drawings and schedules.
Conclusion
From descriptive to prescriptive and proprietary, specifications provide guidelines for the construction of a project that is to-standard and meets the client’s expectations. Nowhere else can you describe in detail how things are to be built, assembled or protected. Developing a clear and concise project specification ensures quality control and quality assurance while greatly reducing the chances of errors, omissions and misinterpretations – errors that can lead to costly delays and disputes.
Looking for more information about specifications? Check out some of our other articles!
