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The scale of residential construction ranges from single houses to apartment blocks and multi-phase mixed-use developments. Across this range, a significant change of understanding is required by the specifier to ensure the right level of quality and efficiency.

Scale is at the core of this dilemma because one-off and small developments are entirely different from mixed-use schemes, apartment blocks, and multi-phase developments. Quite often, errors occur because principles and techniques used for small projects are inappropriately applied to large ones.

Large schemes involve complex standards, regulations and requirements. Where "deemed to satisfy" standards will do for small works, full calculations are needed on the larger projects. This requires a complete change of attitude, knowledge and experience.

Key areas to consider

Fire protection Fire protection for individual homes is straightforward, but apartment blocks need careful consideration. The specifier must consider the means of compartmentalisation and each dwelling must have a fire-resistant perimeter, as must all common areas. Further compartmentalisation will be necessary if the dwelling has any internal dimensions of more than 9 m or is multilevel.

Fire escape cores must be positioned to ensure that flight distances are within the maximum allowed and terminate in a place of safety.

Structure Structural considerations increase in complexity with the size of the development. Frames must also provide fire and to some degree acoustic separation. For this reason, heavyweight concrete is often appropriate. The need for good environmental performance will also require the use of heavyweight construction.

Services Services provision takes on completely different scope with increases in scale. Small-scale rule-of-thumb provisions can no longer apply and all elements need to be calculated and specified accordingly. For example, large developments may need fully integrated control systems.

Heating and cooling requirements must be carefully calculated, although the use of air-conditioning is being made more difficult under the new Part L of the ºÃÉ«ÏÈÉúTV Regulations. Specifiers need to consider the co-ordination of the M&E elements and the building fabric from an early stage of detailed design.

Ventilation Once this was just a matter of fitting a kitchen extractor fan; these days, ventilation needs to be considered for individual homes. The more complex requirements of new Part F and Part L make the inclusion of fully ducted systems in apartment and other large-scale developments common.

Security Security and fire alarm systems must be included in all large schemes. These require a level of understanding far beyond that of most small companies - equal to that of a commercial development.

Circulation Lifts are not a legal requirement but are a commercial necessity in developments higher than four storeys. Their inclusion in schemes below this level is dependant on the market positioning of the apartments.

Vertical circulation needs to be considered carefully and a fire assessment strategy should be undertaken for medium-sized to large projects. For very large projects, complete population flows should be modelled to test the design.

Maintenance Maintenance and cleaning strategies must be considered on most projects at the design stage under the Construction (Design and Management) Regulations. For larger projects, these will be quite sophisticated and need significant consideration.

The neighbours The Party Wall Act and Neighbouring Land Act place duties on the specifier and the team to ensure that the project respects its neighbours and can be maintained appropriately. These may need specialists to be involved early in the design and for the specification of the perimeter fabric to be for highly durable materials that provide easy access. Party wall, floors and structure that are rarely encountered in small projects need to be resilient and ensure that many years of service will be achieved.

Procurement Procurement can be straightforward in small projects but needs to be carefully controlled in larger schemes. The specifier must have a clearly defined brief and ensure that the project details are robust enough to survive the procurement process. It is disappointing that procurement is still the weak link in many large-scale projects, usually because it is isolated, money-oriented and simplistic. The specifier should be aware of these issues and endeavour to influence the client before it is too late.

Other issues Once of the advantages of large projects is their economies of scale, which mean a wider choice of materials is available to the specifier. However, the specifier must consider the use of materials with low embodied energy and also the need to reduce waste on site. Durability, sustainability, quality and workmanship are all significant issues that affect the experience of the home occupant. In small-scale developments, it is understandable that there is a wide range of performance. In larger schemes, these should all be established beyond doubt and delivered seamlessly. It is noticeable that commonly there is a failure to deliver and that can often be attributed to a lack of appreciation of the challenges that develop with large projects.

Watch points

• Small-scale principles rarely work with large projects
• Treating large projects as small ones with bigger numbers is to be avoided
• Look carefully at regulations and standards
• Have systems and procedures in place for large projects
• Make good use of procurement on large-scale projects, but be careful of more onerous standards.