Wiring an open fronted car barn

Wolfie1212 · Jul 2, 2023

Hello, I am an enthusiast amateur undertaking wiring of two outbuilding under a building notice. I am soon to be subject to a first fix inspection by the council appointed electrical company. I have previously wired a large part of my house through the same route achieving a satisfactory inspection and test and the certification. My question relates to an open car barn, oak framed, tiled roof clad in a softwood cladding. There is no other structure to go in, so all will be visible. The building is fed via 16mm2 sub main SWA cable protected via a switch fuse. I have put in an earthrod to allow the building to be TT earthed. The building will have a small consumer unit proving three circuits, 16A radial sockets (two doubles), 6A lighting and 32A car charger. I was originally going to fit doors and treat the building as a watertight enclosed large shed. However, I have now decided that I don't want doors, hence is open to the front face. The roof and walls are watertight. All wiring will be at the back of the building or up in the roof area (for lighting). Given the front is open to the elements, What IP rating should I consider being needed for the internal wiring and components?

Further, I was going to wire in conduit within the building. However, I have a lot of SWA (all sizes) left over, can I use this to provide internal wiring, so avoiding conduit? Will SWA provide sufficient robustness for a garage environment?

Regards

mainline · Jul 2, 2023

Wolfie1212 said:
Hello, I am an enthusiast amateur undertaking wiring of two outbuilding under a building notice. I am soon to be subject to a first fix inspection by the council appointed electrical company. I have previously wired a large part of my house through the same route achieving a satisfactory inspection and test and the certification. My question relates to an open car barn, oak framed, tiled roof clad in a softwood cladding. There is no other structure to go in, so all will be visible. The building is fed via 16mm2 sub main SWA cable protected via a switch fuse. I have put in an earthrod to allow the building to be TT earthed. The building will have a small consumer unit proving three circuits, 16A radial sockets (two doubles), 6A lighting and 32A car charger. I was originally going to fit doors and treat the building as a watertight enclosed large shed. However, I have now decided that I don't want doors, hence is open to the front face. The roof and walls are watertight. All wiring will be at the back of the building or up in the roof area (for lighting). Given the front is open to the elements, What IP rating should I consider being needed for the internal wiring and components?

Further, I was going to wire in conduit within the building. However, I have a lot of SWA (all sizes) left over, can I use this to provide internal wiring, so avoiding conduit? Will SWA provide sufficient robustness for a garage environment?

Regards

Yes

brianmoooore · Jul 2, 2023

Open fronted or enclosed, I'd be aiming for IP55 for everything. Spiders, insects and dust to consider, as well as moisture.

plugsandsparks · Jul 2, 2023

TBH, even if you had put doors on, the ones i have wired i have used surface PVC conduit and "outdoor" types sockets, light switch and IP rated batten light fittings, JCC and powerled do a good range for this application.
The location of the CU is important to avoid wind blown rain. You can still get plastic IP rated CUs and outdoor glands for you SWA. All stuff is easily available, just treat it as a full blown outdoor installation.

Wolfie1212 · Jul 2, 2023

Thanks all, you have just confirmed my thoughts. IP55 minimum plus SWA. I will ensure the main element of the electrics are well out of the way of wind driven rain.