The doorset is a fully finished, engineered element comprising of frame, pre-hung door leaf (with any vision panels) and essential ironmongery, all matched and pre-assembled in the factory. It is delivered to site as a package for reassembly and simple installation.

In contrast, traditional door assemblies consist of the same elements but usually from various different sources, with final assembly and finishing carried out on site - frequently involving different trades.

Leaderflush Shapland doorsets are designed as complete, engineered units to meet specific performance requirements and manufactured to exacting standards from established components under factory conditions ensuring:
  
- Minimised intervention on site
- Consistent fitness for purpose
- Straightforward replication of certified test conditions within the building

Appendix B of Approved Document B

"Any test evidence used to substantiate the fire resistance rating of a door or shutter should be carefully checked to ensure that it adequately demonstrates compliance and is applicable to the adequately complete installed assembly. Small differences in detail (such as glazing apertures, intumescent strips, door frames and ironmongery etc) may significantly affect the rating".

The importance of doorsets is acknowledged by BS 8214: 1990 'Code of practice for fire door assemblies with non metallic leaves':

"It is strongly recommended that pre-hung, pre-finished, fire doors (i.e. doorsets) are specified whenever possible as this reduces the amount of site work necessary and allows normal factory quality control procedures to be applied to the finishing operations."

BS 8214 calls for testing of complete fire door assemblies or doorsets, fully representative of all aspects of how they will be used on site. For door assemblies, this is far more problematic with potential for combinations of mismatched, uncertified components and poor site practices. In addition to fire resistance, other performance criteria can be achieved and maintained more easily with doorsets, including:

- Smoke containment
- Sound reduction
- Durability

This is due to the factory finishing, matching and fitting of the various components which work together to meet performance levels. Other guidance documents recognise this, such as HTM 58 Internal Doorsets:

"The high performance standards required of door leaves, frames and ironmongery in health buildings can best be met when these components are accurately fitted and matched in a factory and delivered to site as a complete unit (i.e. doorset)."

Independent research has addressed commonly held misconceptions about the capital costs of doorsets by using an objective comparison of realistic, current market prices compared with those of site-assembled unitary components. This research used single stage tenders for three real projects from reputable, national door contractors. With all building types considered, savings in capital costs were shown for doorsets over the average for contractors using site assembled unitary components clearly showing that:

Doorsets can save up to half the initial capital cost of traditional door assemblies.

The doorset concept is a well-established example of the prefabrication and off-site product techniques advocated today under the 'Modern Methods of Construction' banner. Current initiatives, based on 'Constructing Excellence' principles, call for greater efficiency and savings in all areas of the building industry, not just construction costs. To satisfy these requirements, research has analysed differences in the procurement process and consequential time implications for architect, consultant quantity surveyor and main contractor's estimator, between doorsets and unitary component assemblies.

This analysis showed that doorsets substantially
simplified the procurement process and offered overall time/cost savings of 50%.

Over 60 different components make up a typical storey height door assembly. It is generally accepted within the building industry that:

Substantial installation time and cost savings are achieved on site with doorsets over unitary component assemblies.

"There is an overwhelming case for the use of performance doorsets in place of site assemblies of unitary door components in today's building industry."