What factors should an architect or builder consider when specifying internal doors and windows? Gerard Daws of Davis Langdon Schumann Smith lists the six essential points that apply to everything from a home extension to a million-pound City fit-out
When specifying internal doors, windows or glazing, the architect or builder should take great care as, if carried out carelessly, the wrong level of information can lead to poor performance, claims for loss and expense or even costly replacement. The following criteria can be applied to all internal door, window and glazing specifications, whatever their size or requirements.

1. What the client wants

The first thing the architect or builder should do is sit down with the client to assess location, purpose and usage. For example, is there a particular fire-rating to comply with, or a glazed room that has a acoustic performance requirement? Considerations include:

  • Strength, security and access
  • Privacy
  • Statutory and local authority regulations
  • Location
  • Fire, acoustic and thermal requirements
  • Light transmission.

2. Performance specification

Next, choose your types of material and installation in accordance with the above:

    Strength, access and security
  • Swipe-card readers for doors
  • Lockable windows
  • Toughened/laminated glazing to withstand impacts
  • Ceramic fritting or opaque/translucent finish to glazing
    Statutory and local authority regulations
  • Be aware of specific requirements for plant and electrical room doors stipulated by utility organisations
    Fire, acoustic and thermal requirements
  • Intumescent strips to door thresholds and edges
  • Smoke seals to doors and windows
  • Keyhole covers to doors
  • Sound absorbent linings between panes
  • Thermal break to glazing
  • Good ventilation to inhibit condensation to glazing
  • Drainage channels for severe locations.

It is usual and advisable to specify doors, windows and glazing as a performance specification. Thus, scope and intent is defined and a series of minimum requirements such as fire, acoustic, structural and environmental are provided in the specification. It is the responsibility of the contractor to propose systems that meet these requirements – thus, liability for any potential failure is transferred. It is important, therefore, that any drawings are purely indicative and do not show all dimensions.

3. Expert advice

Involve manufacturers as early as possible. It allows those responsible for manufacturing a door or window to propose their own recommendations based upon the latest technology and their experience from previous projects.

4. Learning from the industry

A good test of a specification is to discuss it with colleagues and "test" clauses to check that the document covers problems previously encountered. This "database" of the experience of others in the industry is often untapped and can be helpful – plus, it's absolutely free.

5. Samples and benchmarks

Ensure that requirements for submittal are clearly laid out in the specification and that any samples are kept in a safe place, preferably a designated sample room. It is important to know what you are buying prior to the contract signing, particularly for materials of visual significance.

Make it understood that the first type of each door fitted and the structural bay of each type of glazing shall be the benchmark for the installation of all the doors and glazing. Once the benchmark is accepted, it is clear to all parties what standards of workmanship and installation are expected.

6. Testing and submittals

It is important for a contractor to demonstrate that the doors and glazing comply with the requirements specified and the relevant standards. Typical testing includes:

  • Fire doors to comply with BS 476. Additionally, the Loss Prevention Certification Board and Certifire can provide third-party certification of products
  • Burglary resistance of doors to LPS 1175
  • Windows comply with BS 6375: Part 2
  • Sound insulation of glazing to BS 8233.

During the tender process, typical submittals include:

  • Material specifications and literature
  • Any test certificates
  • Method statements of installation
  • Contractors' working drawings (usually post-contract)
  • Any further documents as required in the specification.

Windows, glazing, and interior doors