Although a simple part of the construction process, the electrical system is one that needs to be correct at the design and layout stage as changes later, when the house is finished, are costly and disrupting. It's important to avoid trying to economise when laying out socket positions and lighting points as the material cost of additional sockets or lighting pendants is very low, especially when the cabling is going past the location anyway. Even if adding a few meters of cabling is required, the extra cost is negligible. Looking further ahead, running cable for possible extensions or features in future will cost little now but can save a lot of channelling and replastering later should the work be done. When planning the electrics remember to give consideration to the height and positioning of switches and powerpoints so that they will, if possible, be accessible for someone in a wheelchair.
Apart from ring mains and lighting circuits, other cabling that should be considered at this stage is:
When laying out, ensure that each room has an adequate amount of sockets both in places that require them, for example kitchen worktops and the TV area of a sitting room, and also in places where they may not be immediately needed but would be useful if you rearrange the furniture. This allows the maximum flexibility and the least chance of having to damage expensive wall finishes in future. Consider making all socket positions double gang as there is little cost increase compared to a single gang. This can help prevent having to use plug in multi-way adapters later.
Beyond the positioning of sockets, it is also worth considering the wiring layout. Houses will often simply have one ring circuit dedicated to each floors' sockets but there are worthwhile variations to be made where kitchens are concerned. It's a sensible idea to give a kitchen, and/or utility room, a dedicated ring circuit as it is here that the highest power devices are to be found. Washing machines, kettles and anything with a heating element will draw the largest currents - so it is worth ensuring that the supply circuit will be well able to cope. This avoids the problem of the largest load being at a disadvantageous point on another ring circuit. Bathrooms too, where power showers are planned will need separate ring circuits.
For lighting layouts beyond the single, central pendant and especially in larger rooms, consider putting in multiple switched circuits. This allows great flexibility in illumination, rather than an all or nothing approach, and can dramatically enhance the range of moods of the room, from bright task lighting to subdued and relaxed. Wall lights and picture lights are often only used in living rooms but there is no reason not to incorporate them into the design of almost any room as well as hallways and landings. Lights that can be dimmed will again add to the flexibility, as can multi-way switching so that lighting can be controlled from any doorway into a room and either end, or middle, of a hallway.
A recent feature in modern houses is the use of downlighters; small halogen lamps with a tightly directed spread of light output allowing great control of a rooms' illumination. Whilst highly effective and pleasingly aesthetic, one should be careful about designing large areas that use nothing else as each bulb has a relatively high power consumption and a more limited life than standard light bulbs giving a greater overall running cost.
Where areas are going to be illuminated for long periods, especially in the winter months, such as hallways and landings consider the use of light fittings that use energy saving light bulbs as this can make a worthwhile financial saving. On the other hand, avoid energy saving lighting in bathrooms and en-suites where the warm up lag can be irritating and the instant illumination of incandescent bulbs can be preferable. Cupboards and alcoves can also benefit from being illuminated so allow for such areas to be given their own light; when they are in use and full of clutter, this makes rooting through them much easier!
Sufficient outside lighting is a great benefit for both the householder and for visitors. Apart from the usual lamp by the front door, consider illuminating driveways, side paths and patio areas with either switched or automatic lights for added convenience, security and safety.
IMPORTANT NOTE: In order to comply with regulations and to ensure safety, all electrical installation work should be done by suitably qualified tradesmen.