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Retro-Wiring for Home Automation

While many home automaters have the luxury of specifying their houses from foundations upwards, most of the population still buy a house rather than build their own. So, when HA is considered, the natural choice seems to be to use X10 for everything that is available, and wireless for anything else.

This is an expensive option, and needn't be the only one. With a lot of planning, and a little care, it is possible to run cables in most houses without major redecoration and upheaval. Planning is critical though, otherwise the installation can be a thoroughly frustrating experience.

This document will give you some pointers on some of the things you need to consider before lifting a tool or unreeling a cable.  Like most of the WWW, this is a work in progress- if there's a topic you would like to see covered more, or you have any other comments or corrections, see the contact info at the bottom of the page.

Yes, it is rather long for a single page of html, but someone might want to print it all, and I don't want to have to keep updating 2 versions... the list below will take you to the appropriate section, and the  icons will bring you back to the top.

Although there is a lot of overlap between sections, the information splits roughly into:

Choosing a cabinet location

A typical choice of location for a new build is under the stairs.  It sounds like a good place to put it, it will probably just get filled with junk otherwise, and you're sure you saw a picture on the web of a wiring centre with a diagonally sloping ceiling... You might never have thought of using anywhere else, or you might have considered it briefly and made it your first choice too, but it might be worth considering the options in a little more detail first.

The first requirement is that the location should be central. This doesn't mean that it has to be at or near the geographical centre of the house, but that it should be at a location where there is easy access to wiring routes to all the other rooms in the house.

This decision might be what rules out the understair location. From under the stairs, you have 5 surfaces to go through, the floor, 2 triangular walls, 1 other wall, and the stairs above you. The access to the stairs is often unhelpful, as it's hard to route cables any further once you get to the top. So you will have easy access to any underfloor void (assuming you don't have solid concrete floors downstairs), to the hall, to an outside wall, and to one adjacent room or cupboard.

If you now consider that you can easily have a 4" diameter wiring bundle, where is it going to go next? And what happens if this large mound of electronic equipment under your stairs develops a fault and, in the worst case, causes a fire? It's right in the middle of your house, probably just where you want to pass through to exit.

For all these reasons, you might want to look elsewhere. Just about all older houses have chimney breasts in most of the rooms, and many of these have cupboards built on one side of the chimney, in the alcove. In fact, there is often a matching cupboard on the floor above as well. These are an ideal cable route to get from ground floor level into the attic (or underfloor void if available), leaving only the horizontal part of the run to complete.

The length of the cables might increase a little by putting the cable closet further from the true centre of the house, but installation and maintenance is much easier. Time spent thinking about the location can be repaid many times over when you start to install everything.

It is important that there is easy access to the wiring centre. For a start, you, or someone you pay, is going to be spending a lot of time there during the installation, terminating cables and installing equipment, so it will pay to make it as accessible and comfortable to work in as possible. Make sure you can get access to a ring main nearby for power, or to the main fusebox/consumer unit if you want your HA equipment to be on its own fuse/breaker. It is worth planning the aesthetics too- will there be any visible evidence that this is the geek closet? If so, can you make it not visible, or would another location be better?

Wherever you choose, it is almost inevitable that you will one day need more equipment than you are installing at first. There's no harm in it being a part of a cupboard at first, as long as you will be able to expand into the rest of it if needed. However, for safety's sake, as well as the well-being of the equipment, it's best not to use the bottom of a fitted wardrobe, surrounded by flammable, and thermally insulating, clothes.

This raises another issue, ventilation. If you have a couple of amplifiers for whole house audio, maybe a PC, and other electronic odds and ends in the cupboard, it could all get rather overheated. Give some thought to arranging an airflow past the equipment- this could be as simple as a ventilator opening at the bottom of the cupboard and one near the ceiling, above the highest equipment. Covers for ventilating chimneys into rooms or covering airbricks are inexpensive, and easily available at DIY stores.

This has been mentioned a couple of times already. Without wishing to scaremonger, do think about what you can do to make things safe. For instance,

I'm also fitting a smoke alarm in the equipment closet, but time will tell if it causes too many false alarms to be useful. If so, a simple temperature alarm or heat detector might be more useful.

You might decide to fit LSZH cables (low smoke, zero halogen) instead of the normal types. These are often specified in offices, but I've not seen any compelling reason to use them for my installation. If anyone knows differently, let me know! One possible reason might be colour coding- LSZH are usually purple-jacketed, and may be cheaper than ordinary colour coded cables from some suppliers!

Identifying cable routes

If you are fortunate enough to have floorboards, as opposed to chipboard flooring, it should make the job easier. Small sections of board can be cut out and replaced fairly easily. Remember that the joists (the wooden beams which the floorboards rest on) run at right-angles to the boards themselves. You can run cables unobstructed alongside joists, but if you need a run in line with the floorboards, you will probably have to lift a complete floorboard to drill holes through the joists.

If possible, it is best to avoid drilling joists if there is another good route available, but holes up to 1" diameter, drilled in the middle of the joist, shouldn't cause any problems. Don't drill the joists near where they rest on structural walls, try to get at least 1m away if possible.

These spaces are what makes retro-fitting wiring bearable! The easiest way to run cables would be vertically from the wiring cabinet to the attic or underfloor, horizontally to the right wall, then vertically up or down the wall void to the required location. The final stage is always complicated by additional horizontal supports in partition walls, and there is no easy way if the wall is solid (brick or stone) rather than hollow (lath and plaster or plasterboard).

When running a cable in an underfloor or attic space, don't be tempted to run it on a diagonal to get the shortest distance between two points. When you, or a future resident, comes to work in the underfloor or attic, or convert the attic to another room, it will take much more work to rearrange the cables than to do the job. Most cable is cheap, around 10p/metre for Cat-5, and it's really not a worthwhile saving. Run cables around the edge of the attic, don't run them in any V-shaped sections of roof truss (there will inevitably be some movement, and the cable will eventually be damaged), and basically consider what you or others might be doing with the space in future. In underfloor spaces, keep the runs tidy, ideally secured to the base of the joists supporting the floor above in bundles.

With a lot of planning, you can really cut down on the amount of decoration damage that is caused as you install everything. If you are lucky, or not in a hurry, you can run cables close to their final destination in soon-to-be-decorated rooms, and leave enough coiled up in the ceiling space or underfloor, then do the final run before decoration. Careful use of the tools mentioned below should save you making more holes than are absolutely necessary. Spend some time poking round your house for good cable routes (in my case, the top of the first floor lath and plaster walls are open slots in the attic floor, which is a big help), and try to run the cable in easy routes as much as possible. Most systems (audio, video, ethernet etc) will quite happily run down 100m of cable, so don't worry if the route seems rather long if it makes it easier to install, and results in less ‘making good’ at the end.

The wiring in your home should comply with the IEE Wiring Regulations which were in force when it was last rewired. If it did, and the wiring is safe (ie not currently needing replacement), all mains cables should either be buried 50mm below the surface, mechanically protected against damage, or within recognised areas in the wall and ceiling. These areas are within 150mm of a vertical or horizontal line from any electrical outlet, switch or cover plate, or within 150mm of a horizontal or vertical corner.

However, it is likely, that there have been additions made since the house was last rewired, and either they, or the rest of the wiring might not meet these requirements, so do drill with care. Perceived wisdom is that parallel runs of mains cable and data/low voltage signals should be kept apart. Recommended distances are at least 12"/30cm (24"/60cm in the US- lower voltage, higher current) to avoid interference, so do try to plan runs where it is unlikely that there is mains cable nearby. Typical joist spacing in a UK house is 16", so as long as the cable is running between different joists from the mains, it should be OK.

There is one other service which is widespread in homes which might be more helpful- plumbing. If floorboards have been lifted to install central heating, and there are no mains cables in the same spaces, it will make access much easier for you to make holes to run your cables through. Don't run cables through the same holes that pipes use, and keep cables clear of pipe carrying hot water or central heating connections, as they will get hot and might damage the cables, and they do move to some extent as they heat up and cool, which will also damage cables pressed against them.

Useful tools

There are a number of useful products which extend your reach enough to manipulate cables through awkward routes. Most are inexpensive, and it's useful to have them all (with the possible exception of fish tape, which is more useful for drawing cables through ducts and conduit than open voids).

Drain rods- approx £20. These are the single most useful tool for pushing cables underfloors or along between attic rafters/hangers. Typically you get about 8-10off 1 meter long 'sticks', a 4" rubber pad (to clear drains), and an auger attachment, 2 spirals of metal bar designed for particularly persistent drain blockages (yuck!).

The auger is probably the most useful part of the package though, as it can also be used to grab a loop of cable pushed down through a floor at one point, which can then be pulled towards you. The removable poles make the whole thing manageable as you can add them as you push the pole along. The assembled rod is surprisingly flexible, but has enough rigidity to push past obstructions.

One important tip- don't tell your neighbours that you own drain rods until you've run all your cables- once they've been used for sweeping chimneys and clearing sewers, you won't feel quite so keen to use them again!

Net curtain wire, a metal coil with a plastic sleeve, is often useful to guide cables through small holes, and a 'pearl catcher'(one of the 1/2m or 1m long ones often sold in small tool shops) is useful for fitting through small gaps or getting round corners which are too tight for a drain rod.

String- it's useful to run a length or two of string with any awkward cable runs so you can pull future cables through more easily. It is also useful to make plumb bobs to drop cables through cavities.

Fish tape is a fairly rigid material, either like a tape measure, or sometimes a fibreglass pipe, which can be used to prepare a route for cable, it can be juggled about and allows some pressure to be applied to work it through small holes to the destination. Once there, the cable can be fixed securely to one end and pulled through (along with a length of string for next time!)

It is worth having at least one large masonry drill bit, say 400mm long, 16 or 20mm diameter, to make runs through solid walls. If the wall is external, make sure it slopes downwards towards the outside so any water will tend to find its way out rather than in! A selection of wood bits is also necessary. A large masonry drill bit costs about the same as a cheap electric drill, (£15-£20), but is worth having to hand!

It's always dark somewhere in the cable route, and if you drill through a mains cable and all the lights go out, it's useful to have one to hand!

This is one tool that I have not personally used, but it has been recommended. It can be used to extend a drill chuck, round corners etc, and seems like a useful item for drilling through the horizontal supports encountered in partition walls. They are available from various DIY suppliers, including Screwfix ( If anyone has experience of using one of these, or knows a good make to get in the UK, let me know!

Running the cable

Get as many cable drums or boxes as possible- it might seem cheaper to get 1 305m box than 3 100m reels, but if you have to run 3 identical cables to each location, it could quickly get irritating! Try to get the assistance of at least one other person, 2 might be useful occasionally, and if the extra person is not needed, at least someone can be having a break, going off to buy doughnuts or make another cup of tea!

Choose the appropriate cable type- there is lots of information on the net about this, and US cable types are generally readily available here. I personally am using UTP Cat-5 cable for most things, and STP (screened twisted pair) for unbalanced analog connections (and Comfort keypads) and connections in electrically noisy areas (eg in the kitchen).  Separate cables are allocated for

and each room gets what it needs, or is expected to need, where it needs it.  It is not a good idea to mix any of the above on one cable.  If you subsequently find that you really need ethernet in your bathroom and you hadn't planned for it, it might be possible to rejig the other cables so that it sort of works, but you certainly shouldn't plan to do that.  Cable is cheap, running it can be difficult, so either overestimate your requirements, or at least add '1 for luck' on all but the easiest runs.

If you are doing this yourself, you probably won't have the chance to do it all in one go (unless it is part of a new build), so part of the planning is in splitting up the cable-running.  If you plan carefully, you can run a number of cables along the same route, with some stopping at different places, rather than having a spiders web of individual cables going everywhere.  As a rough rule, in an evening or half a day, you can probably run any number of cables to one location, and fix wall plates and terminate a few cables in another half day or evening.  Don't try to do it all in a hurry, as something (or someone) will probably get damaged, and you will get frustrated.  There will be some easier runs (one of mine is about 2m), and some harder ones, so don't start on Saturday lunchtime if your boss is coming for tea at 6...

If you are doing the work gradually, terminate cables as you go.  I'm using Krone IDC blocks, and I'd recommend them if you are running cat-5 or similar cables.  They are very quick to terminate reliably (speaking as a fast solderer!), and make future modifications quite straightforward.  Plan first though!  Get a piece of paper (or draw a table in your favourite word processor), and plan where all the wires will go.  When something stops working, or you want to change a phone outlet onto a second line, you will regret it otherwise!  And when you are done, photocopy the plan, and keep a copy in the wiring box!  AND DO UPDATE IT when anything changes!

Always label the cables as you run them.  Ideally, mark them at each end with some system that lets you know where the other end is.  Coloured insulating tape, stick-on cable numbers, marker pens and clear heatshrink, and any number of other systems are available.  Just pick one, write it down, and stick to it!


These are just back-of-envelope figures to give you a chance for a quick calculation of how much it will all cost.  They're all inc VAT (not that it matters with a +/- 50% guesstimate tolerance!)

10-15m of cable per average run- £1.50 (about £35 for a 1000ft/305m box of cat-5 cable)

Krone terminations per cable- £2 (301 box (holds 10x237A terminals) costs about £15, 237A terminals (10 pairs of wire) about £4)
Phone socket/similar- £4 per cable
All tools suggested above- £50

Other Sources

There are lots of other sources for cabling information, although there is little out there about fitting cables in old houses, particularly in the UK, where there are probably some unique constructional methods used in older houses. (Actually, some folk are living in houses older than the USA, but that's another matter!) has a number of articles with details on home wiring, all with a US emphasis. is a good US guide to all aspects of data wiring.

The FAQs from the Usenet group uk.d-i-y, currently stored at, contain a wealth of information on things electrical in the UK, including some useful hints on running cables in cavity walls at is a US security dealer, with good FAQs online at

You might also get help on the usenet groups uk.d-i-y, comp.home.automation and ask politely, and search for the group's FAQ list to see if your query has been raised annoyingly often. You can also use Google's Usenet archive search at to search for FAQ lists or postings on a similar topic to your question before asking.

And last, but by no means least,, the centre for all things UKHA!