Specifications in construction
This article is all about Specifications in construction
Introduction
You already know what a specification is, just maybe not in relation to construction.
When is the last time you bought a new computer or a new phone — you checked the specification right? For example you checked the battery length, the screen size, how many photos it could hold, the colour.
For example, if you walk into a subway sandwich shop the specification of one of their sandwiches is simply all of the ingredients that go into the product e.g. bread, lettuce, cheese, meat, footlong or just half a sub and so on.
Developing and agreeing a specification is how you guarantee that the product you get is the product you order.
Specifications in construction are simply a description of the work that is being carried out. Its not concerned with the quantity of works but instead the nature of the work itself.
In construction you might be installing new blinds to windows and there will be a specification for the blinds. The blinds might be made of Solid PVC, be cream in colour, have anti-ligature metal chains and be head fixed.
Architects when designing a property will choose a specification for each part of the building. We are lucky that there are thousands of standard specifications that the Architect can simply choose and not spend time writing out detailed descriptions.
What is the advantage of a specification ?
Specifications are all about control of the final product.
A specification allows the Client to state unequivocally what they want. The specification is always, together with the detailed design drawings, a contract document. If the Client wants Velux branded rooflights then they must state this in the specification.
If the builder does not install the product that is mentioned in the specification then the Client can insist it be removed and replaced or a credit given to the Client.
The specification is the bible that everyone turns to when checking what materials or products to use. It allows the design team and construction team to communicate with each other clearly about what products are expected to be used.
It allows a level playing field for competing contractors to price the exact same product.
If you don’t have a specification the builder will have no idea what products to use or what finish to apply. There is limited information on a drawing for the Architect to clarify these key pieces of information.
A specification can be a really useful document to give a Client at handover of the building. The Client will have written confirmation of every product and material used in the building. This is called the as-built specification and is the original specification update to reflect what was actually installed.
What should be in a specification ?
A specification should only contain descriptions. It should not contain drawings or sketches. These are to be kept seperate. Also a specification should include quantities, these can be expressed in the schedule of work or bill of quantities.
A specification should list out every product and material that is going into the property.
The specification will contain a mix of performance, prescriptive and proprietary information.
Performance information: If a product need to meet specific performance outcomes in terms of thermal, acoustic, waterproofing, durability or compliance with a building standard it will be stated here. e.g. U Value
Prescriptive specification: type, material, operation, workmanship, related standard of each product
Proprietary specifications: If the architect specifies a specific product e.g. Velux roof windows then it has to be that product that is installed. However should the Architect state “equal or approved” the builder can install an alternative to that brand.
The Architect can use whatever specification they want. They can create a bespoke specification using say Microsoft word or excel or they can use an external provide to assist them in creating the specification.
Some private companies provide software that can build specifications on your behalf.
What should a specification look like ?
A specification is usually an A4 portrait oriented document.
Important attributes include:
- table and contents and page number to allow easy navigation of document
- language should be clear and concise, easy to read
- avoid abbreviations, detailed technical terms, loose or ambiguous language e.g. ‘use good brand light fittings’
- document should be Neat, Professional looking and Visually appealing
- consistent font and size throughout the document
- consistent header and footer style
- only address the main contractor, the document will be used as a contract document between the Client and the Main contractor
- specify the actual outcome and not the process – put the risk on the contractor
The NBS (National Building Specification)
In the UK, the NBS (National Building Specification) is a popular choice for standardized specifications.
A NBS specification can be a massive document regularly coming in at over 500 A4 pages!
The document is split into sections each of which are distinguished by a letter of the Alphabet e.g. section a, b, c and so on.
Every section represents a different category of materials, products and components. For example Section N10 is for is for “General Fixtures/Fittings & Furniture”.
Every product has a separate code within the section. For example window blinds are usually code 240 so they can be found at reference N10:240.
History of the National building specification
The NBS (National Building Specification) was owned by the Royal Institute of British Architects (RIBA). In 2018 the RIBA started to sell their position in the NBS and it ended up being owned by a Swedish information services provider called the Byggfakta Group.
Important -avoid duplication of information
Please note that when creating drawings and specifications that detailed information should be kept in the specification and not in the drawings AND specification.
If the specification needs to be changed then it will need to be changed on the drawings as well leading to a duplication of work.
Some Architects will avoid using a specification and instead cram all of the specification onto the drawings themselves leading to a very unattractive drawing that is difficult to access.