What is building wire


Dedicated elf
Apr 9, 2014
Looking at options for power cables and came across building wire. Two lots of single core is cheaper that one lot of figure 8. I figure the insulation is probably pretty thin and not designed for outdoor use or there is some other quality issue.

Come to think of it is any cable insulation suitable for exposure to sun.


I love blinky lights :)
Community project designer
Dec 27, 2010
Building wire is what is used for the internal wiring of houses. 1mm building wire for instance is probably 7 strands of copper whereas 1mm flexible wire could be something like 40 strands. The cross sectional area is the same but the building wire is a lot more rigid and is more likely to break if flexed a a fair bit or if twitched together. From experience the red builders wire fades a fair bit in the sun when left for a year or 2. I have no idea how much the insulation breaks down in that time though. I've used it outside as an alternative to using 8 gauge wire for tying up a gate so it hasn't really needed a very high insulation resistance.


I have C.L.A.P
Global moderator
Apr 26, 2010
Albion Park NSW
Building Wire is as the name says used for buildings. ie. permanent installations where there is never any movement of the cable once installed. A lot of cheap building wire is also solid core meaning just the one thick copper strand or as Alan mentions using may be 7 strands for the stranded building wire. The copper properties of this cable usually is also a lot less flexible and can easily break if disturbed to many times or if kinked. It is also not UV rated as it is not designed for outdoor use.
The insulation of building wire is rated for 240Volts so its not really the insulation that is the issue but the number of strands and copper quality.