Design & Installation Services for New-Build Properties

If you're building a new-build property for the first time, you'll be finding your way through trial and error. However, you'll have known well in advance about the need to pay an architect to design your property, and a builder to put it all together.

Why employ an architect? Why not just get the builder to turn up with a load of materials and work it out as he goes along? Obviously, your architect ensures a number of things, including that your property is suited to its purpose, that it functions properly, that it's safe, that it is a properly engineered structure, and that it complies with building regulations.

The same applies to your electrics. Some first-time developers expect an electrician to turn up with a van full of cables and throw them all in to the property in a couple of days. Don't overlook that a professional, experienced electrician will want to spend some time designing the electrical system before even considering laying the first reel of cable.

Electrical design is more complex than you may have expected. Design considerations include:

• Complying with building regulations, for example by provision of adequate numbers of socket outlets, and ensuring cables are routed appropriately through joists. (You don't want to have to replace the joists after somebody inexperienced drills the holes in the wrong place.)
• Ensuring the fire detection system is adequate and compliant with building regs requirements.
• Dividing the house up into an appropriate number of circuits, based on expected loads and use, taking into account cable capacities (below).
• Calculating "diversity" of each circuit to ensure design current is specified correctly.
• Calculating cable capacities for each circuit. This is complex and depends on factors including length of cables, current, routing (such as whether cables are being laid under insulation, or pass through insulation, or are grouped together, or are in areas with above average ambient temperature...) Overspecified cables are expensive and difficult to work with, but underspecified cables will represent a fire risk.
• Calculating voltage drops for each circuit, to ensure too much energy isn't lost in a long cable run.
• Producing wiring diagrams based on the architect's base drawings (we use industry-standard CAD systems to do this).

In some very simple cases, standard circuits can be used (for example, 32A ring mains using 2.5mm twin & earth cable up to a certain length), but in modern houses, the structure of the house, particularly where underfloor insulation and non-traditional building techniques are used, means careful design and calculation must be undertaken to ensure the wiring is safe, adequate and BS7671 compliant.

Only then will an electrician start to wire everything into place.

You may therefore want to consider whether the guy who gave you a quick price over the phone, who happens to be the cheapest, is going to do the job you want. You certainly wouldn't choose your architect on this basis!