Cabling for garden room

Hi all.

First time poster. Currently running 252/300 with ndx2 and sopra 3 speakers. Some witch hat goodness thrown in.

Im currently building a stand alone building for hifi/cinema in my garden. Its a new build house so ive got the opportunity to cable where i need to as they go.

So my question is around running power to the unit. The hifi will have its own supply from the meter to a dedicated CU and its own earth etc…seperate from the ither supplies to the unit for lights etc.

I need to run the live underground for a good 30 metres to reach the unit. Id like some advice on what spec I need to be using please?

As with all things hifi the sky is the limit. What have you guys who have built similar done?


You don’t say where you live, so it’s probably best to speak to an electrician locally. For what it’s worth, my dedicated mains runs round the outside of my house, under the flower bed, and uses 10mm2 SWA.

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My HiFi socket is connected by 35 meters of 10mm2 SWA cable - works a treat for a UK installation.

I’m not surprised that you’re asking that question here.

I did the separate supply thing earlier this year and the electricians didn’t seem to want to accept what was being asked of them.

Your scenario throws up more questions in my mind than what I had to deal with.

The distance being the first thing. I used 10mm² on a 10 metre run but I was under the impression that you’d need to get something even beefier if you’re going to run a 30 metre length.

Hopefully someone who is qualified will speak up.

Another thing is, how the hifi would be separated from the rest of the electrics in the room.

Would you need to run two separate supplies from the house?

One for Hifi. One for everything else.

Or, could all the power be run down one super beefy supply line and then separated into two consumer units (one for Hifi and one for everything else) with separate earths.

Yet again, hopefully someone who is qualified will speak up.

Those are the first things that come to mind. But surely someone here has already done this previously.

Welcome to the forum, by the way!

If you are in UK, you need to consult a qualified electrician, Part P regulations specific to underground cabling will need to be met. Actual cable size and how it’s connected to incoming mains will be part of that discussion. The work can be done DIY with the final connections by the electrician and that will include inspecting the DIY stuff as part of Part P papers.

As above @Mike-B. It’s not just a question of installing what sounds best for your hi-fi but rather more importantly about ensuring compliance with the appropriate regulations.

Advice should come from a qualified electrician rather than from hi-fi enthusiasts.

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You need to be careful with what you will have plugged in over and above the hifi. For instance, I also have an electric heater in my cabin and plan to run a spur over to a new garden shed next year so measure once cut twice. I’d have a conversation with an electrician as there are other decisions to be made re: earthing etc. Also you need to consider internet access. I’ve been using a mains extender but this creates noise that is picked up by my phono stage so has to be switched off when playing vinyl. My streamer then needs to be rebooted when it’s switched on again to reliably reconnect, so I’ve just run an Ethernet cable to a Wi-Fi access point in my cabin to mitigate this. Wish I’d done it at the same time as building the thing.

Thanks everyone, apologies for not being clear. I am in the UK. The guys building the house/unit have a qualified electrician who I am working alongside.

I wanted to over engineer the setup - I’m not just digging a hole and throwing it in myself.

It seems like most are using 10mm2 SWA

OK, it seems like you are on the right track already as your post says
The hifi will have its own supply from the meter to a dedicated CU and its own earth etc ……
and …. separate from the ither supplies to the unit for lights etc.
Now you say you have the electrician already on the case.
Good stuff, and I would agree 10mm/2 SWA is the way to go

Presumably you have seen the diagram below. Perhaps pass onto your electrician

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I think he’ll need another CU in the garden room.


The new CU next to the existing one may serve this purpose as the hifi room would in this case be essentially a spur. Of course I bow to professional knowledge here.

I will say this forever to posters here, where are you? @Ianm83 regs are deferent everywhere!

He did confirm earlier that he is in the UK :blush:

I think I would be inclined to have a HiFi CU next to the meter, just for a HiFi socket via 10mm SWA, and then for all other items in the garden room, I would then run a 4mm or 6mm SWA off the main CU to a separate mini CU in the garden room to cover lights and any non-HiFi sockets. That ensures that lights are not on the same cable run as the HiFi.

Just an idea for consideration…

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The usual way an electrician would wire an outbuilding is to run a single feed, probably from a spare way in the main consumer unit if there is one. Then a small consumer unit in the outbuilding would allow this feed to power two or more separate circuits for lighting, sockets etc.

If you want a dedicated HiFi circuit you ideally want it to be independent from the main house consumer unit, which means splitting the connection from the meter before it reaches the main CU. That means you would need a second cable from an additional small CU near the meter that supplies a socket or two for the HiFi. Some electricians will insist that thus is unnecessary or that you are a nut case. You may need to get a few quotes if you want an electrician who will take your requirements on board.
Otherwise you can take the dedicated circuit from the additional CU in the outbuilding, but that’s a compromise on what a dedicated feed really is.

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Bit of a change up guys. Ive done a deal this week to upgrade to a statement. So id like to leave no stone unturned on this now.

Yes I know I need to upgrade sources and speakers - rome wasnt built in a day and my dealer had this statement up for grabs now. So I took my chance.


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(Do you need to upgrade size of room for Statement system?) More particularly, have you planned its design for best acoustic performance, bearing in mind that cinema and hifi can have different room requirements? (A couple of years ago when a house move was a possibility, I started trying to design a room within constraints of an existing structure, seeking to balance the demands for best of both hifi and home cinema, and it was quite a challenge.)

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