- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 01 Apr 2018
Specification for construction
Specifications describe the materials and workmanship required for a development. They do not include cost, quantity or drawn information, and so need to be read alongside other information such as quantities, schedules and drawings.
Specifications vary considerably depending on the stage to which the design has been developed, ranging from performance specifications (open specifications) that require further design work to be carried out, to prescriptive specifications (closed specifications) where the design is already complete.
Having a prescriptive specification when a contract is tendered gives the client more certainty about the end product, whereas a performance specification gives suppliers more scope to innovate and adopt cost effective methods of work, potentially offering better value for money.
Typically, performance specifications are written on projects that are straight-forward and are well-known building types, whereas prescriptive specifications are written for more complex buildings, or buildings where the client has requirements that might not be familiar to suppliers and where certainty regarding the exact nature of the completed development is more important to the client.
An exception to this might be a repeat client such as a large retailer, where a specific, branded end result is required and so whilst the building type is well known, the specification is likely to be prescriptive.
Most projects will involve a combination of performance and prescriptive specifications. Items crucial to the design will be specified prescriptively (such as external cladding) whilst less critical items are specified only by performance (such as service lifts).
- Large clients may be able to procure certain products at competitive rates themselves (for example the government).
- Some designers may have particular experience of using a specific product (although some clients may not allow designers to specify particular products as they believe it restricts competition and innovation and may relieve the contractor of their liability for 'fitness for purpose').
- The contractor may be best placed to specify products that affect buildability.
Specifications should be developed alongside the design, increasing in level of detail as the design progresses.They should not be left until the preparation of production information. By tender they should describe every aspect of the building in such a way that there is no uncertainty about what the contractor is pricing.
Aspects of the works are generally specified by:
- Products (by standard, a description of attributes, naming (perhaps allowing equivalent alternatives) or by nominating suppliers).
- Workmanship (by compliance with manufacturers requirements, reference to a code of practice or standards, or by approval of samples or by testing).
Specifications should be structured according to work packages mirroring the separation of the works into sub-contracts. This makes it easier for the contractor to price and so may result in a more accurate tender.
A standard classification system should be followed such as Uniclass.
 Related articles on Designing Buildings Wiki
- Building information modelling.
- Bill of quantities.
- Common Arrangement of Work Sections (CAWS).
- Concept drawing.
- Construction drawing.
- Contract documents.
- Form of tender.
- Insulation specification.
- Manufacturer’s certificate.
- Model Format for Building Services Specifications BG56 2016.
- New Rules of Measurement (NRM).
- Output-based specification.
- Outline specification.
- Performance specification.
- Service level specification.
- Specification basics.
- Standard Method of Measurement (SMM7).
- Technical specification.
- Uniclass 2015.
- Value management techniques.
- Window and door schedules.
Featured articles and news
A PQP describes the activities, standards, tools and processes necessary to achieve quality in a project's delivery.
How Lidl has been actively working to reinforce their brand through sustainability.
Association of British Insurers describe full-scale cladding tests as 'utterly inadequate'.
This article examines the changing policy commitments and evolving definitions of the zero carbon home.
Researchers believe they may have created a 'game-changing' new form of concrete using graphene.
Grouting refers to the injection of materials into a soil or rock formation to change its physical characteristics.
Part of Designing Buildings Wiki, BREEAM Wiki will advance knowledge sharing for the BRE family of sustainability tools.
From the decorative to the utilitarian, and from the photographed to the forgotten.
New BRE book considers the progression from project-based knowledge creation to whole-life urban knowledge management.
This CIOB article explores the concept of value in building design and construction.
Rogers Stirk Harbour + Partners' release new images of soon-to-open 3WTC tower in New York.
A document can be called a bond or a guarantee. Does the name matter and what is the difference between them?