Junction boxes are one of those items that almost never appear on the quote but constantly run short on site if they aren't calculated properly. There are three types and each has a different function.
Accessory boxes (universal)
They go behind every switch, socket or light point with an accessory. You need one per accessory in the installation: in a 90 m² home with a high electrification level, between 45 and 65 units is usual.
Junction boxes (connection)
They are installed at changes of direction in the installation and at points where several cables are joined before continuing to the accessory. As a practical rule, allow one junction box for every 2–3 light points or every relevant change of circuit, plus one for each ceiling where several light points meet.
Consumer unit access boxes
In addition to the consumer unit itself, it is usual to leave one or two large access boxes near it to house joints of circuits that don't fit directly in the unit's box, especially if there are many high-electrification circuits.
Forgetting these boxes in the quote means buying them on the fly, with trips to the shop that stop the job. It is better to add them from the start, even if it is a small item.
Want an electrical quote that leaves no small item out? Try it free in PresupuestoYa.
Want to calculate this quote automatically?
PresupuestoYa calculates materials, quantities and total cost in minutes, for this and 19 other trades.
Create a free quote →