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Adding your own electrics to a garden office

If you are looking to add your own electrics to a Dunster House garden room, or a garden shed that doesn't have any wiring, then please feel free to follow the guidelines below. Please note that if you are not confident, it is recommend that you speak to a qualified electrician who can help you with the installation and the connections. Please note that the following is only a guide.


You will require grey twin and earth in 1.5mm thickness for the lighting. 

Firstly - take a feed from the consumer unit direct to the switch, running the cable in safe zones. Safe zones are vertical and horizontal directions (not diagonal directions). Leave enough cable to work with in the switch (for later)

Take another grey cable, and go from the switch to the first light. Create a small loop (about 100mm loop for the lamp connection) and continue to the next lamp location. Continue for all lamps, until ending the cable at the last lamp. There is no need to return to the switch or the consumer unit.)

Once all the cables are in place, cut the loops at the lamp locations so that you have a two pairs of tails (except the last lamp). Strip the cables by about 30mm and inset the two brown cables into the corresponding live terminals. The two blues to the Neutral terminals and the copper unsheathed cable to the earth terminals. .

Electric Cables

Light Switch

Once all of the cables have been fitted to the lamps, return to the switch and pare back both grey cables so that there is about 75mm of the twin and earth cables visible before the grey sheathing starts.

Starting with the copper cable - cover the two together in a green and yellow earth sheath, then screw them into the earth terminal, which is usually on the back of the switch.

Then strip about 20mm of both blue cables and connect them together using a cable connector. This will simply be positioned in the back box at the end of the wiring. 

Finally expose about 20mm of each brown cable ready to attach to the switch terminals. 

The brown cable from the consumer unit goes into the COM port, and the brown cable that goes to the lights is fitted to either terminal 1 or 2. 

Once they are fitted, screw the faceplate back on to the back box.

Installing Electrical Outlet


Create a ring main using grey twin and earth from the location of the consumer unit to each socket and back to the consumer unit. Make sure that the cables run in 'safe zones' which are vertical or horizontally in line with socket locations. Cut out the wall lining for the back boxes to be recessed, or screw surface mounted plates to the lining board. Create a loop at each socket location so that you can cut the wire and have enough free cable to connect to the faceplate. 

Strip the grey covering to expose about 70mm of blue, brown and copper cable. Strip back about 5mm of blue and brown insulation to expose the copper cable. 

Insert the two brown cables into the live terminal. Insert the two blue cables into the Neutral terminal. Add a yellow and green sleeve for the copper cables, and insert both wires into one of the earth terminals. Repeat for all sockets.

Resetting Fuse Box

Finally the Fuse Board

A garage consumer unit from the DIY stores are a good option when purchasing a fuse board for a garden office, as they are up to date with the correct protection, and are already populated with the correct breakers. 

The lighting circuit needs to have the 6Amp breaker, whilst the sockets can be either 16Amps, 20 Amps, or 32 Amps - all of which are suitable for a ring main. 

Firstly create an opening in the fuse box for the wires to come into - Usually a hole in the back is the place to put it. Then remove the front and fix it to the wall, poking the wires through into the chamber.

Install all of the Earth cables to the earth bar terminals on the top of the fuse box. (Add a green and yellow sheath to indicate they are the earth wires)

Install all of the blue wires (except main power feed from the house - which is usually armoured cable) into the Neutral bar terminals - opposite the earth terminals.

Install the two brown cables for the sockets into the top of the larger breaker (32Amp). These are the two thicker brown wires.

Install the brown cable for the light switch into the 6Amp fuse. This is the thinner brown wire.

Add the armoured cable by installing the Earth cable to the earth terminals. 

Add the Blue cable to fuse above the thick blue flex cable that has already been fitted by the manufacturer in the fuse board.

Add the Brown cable to the RCD (usually next to the Blue cable - and before the 32 and 6 Amp breakers. 

Connect the bottom of the RCD to the lighting and socket breakers at the bottom of the fuse using the four pronged copper connector that comes with the fuse box -adding the plastic sleeve on the copper connector.

Replace the front of the consumer unit, and connect the power at the other end.

Before going live, you may want to get a qualified electrician to test all of your connections. Please note that this is only a guide on how to install your own electrics.

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