Algeria AgencyIT infrastructure
The cabling you did not lay: taking over premises already wired
No plan, no certification report, and sockets nobody can trace. What to test, what to reuse, and what the lease decides.
The article accompanying this one deals with cabling you have installed: where to put the cabinet, a hundred metres not to exceed, the installation mattering more than the category, and everything decided before the walls close.
It is the right article and it assumes something most businesses of this size do not have: the choice. You are taking over premises already wired, by somebody you do not know, on a date nobody knows, with no plan and no report.
The question is therefore no longer how to cable well. It is: what is there, what works, what can be reused, and what are you allowed to touch.
That last question is not technical and it often decides all the rest. In rented premises the cabling rarely belongs to whoever uses it, and the section dealing with that is the one electricians do not read.
What you inherit, and what you do not
You inherit cables in walls, wall sockets, and — with a little luck — a cabinet somewhere. Everything else is missing, and it is worth saying so before you start so that you do not go looking for it.
There is almost never a plan. There is practically never a certification report, and the companion article explains well why that document is the only one that proves anything: certifying means measuring with an instrument, not plugging in a laptop and observing that it works.
You do not inherit knowledge of the category either. The marking on the sheath exists and can be read — wherever a length of cable is visible — but it says what was bought, not how it was installed, and the installation is what decides.
You do inherit something real and underrated: routes. The conduits, the drilled passages, the drops down walls are most of the cost of any installation, and they are there.
The right way to regard taken-over premises is therefore this: the cable is uncertain, the route is an asset. Everything that follows consists of finding out which of the two constrains you.
The first act: open the cabinet and photograph it
Before any test, before any quotation, before even counting the sockets: open the cabinet or enclosure and photograph it as it is.
The photograph does two things immediately. It fixes the initial state, which protects you from a disagreement if somebody works on it afterwards; and it can be studied calmly, which lets you see things you do not see standing in a corridor with a torch.
What to look for in that photograph amounts to five points: a patch panel or its absence, the number of occupied ports, the presence of labels, how the patch leads are organised, and what is powered — the switch, the router, what is blinking and what is not.
The absence of a patch panel is the observation with the heaviest consequences. The companion article gives a section to saying it is not optional; without one, cables arrive directly in the switch and every future intervention pulls on cables fixed in walls.
Photograph the premises too, with the wall sockets visible, and the suspended ceiling open if it opens. Those images will serve every quotation you request, and they save three separate site visits.
What a day of testing settles, and what needs an instrument
Two levels of verification have to be separated, because you will be sold the second when the first is often enough to decide.
The first is done with a laptop, a lead and some method: plug in at every wall socket, note whether the link comes up, at what speed it negotiates, and identify which cabinet port it corresponds to. That takes a day in premises with twenty sockets and it answers the question "what works today".
The second is certification proper, with an instrument measuring attenuation, crosstalk and length. It answers a different question: "will this link carry the load and last". The companion article defines it and it has a cost per link.
The rule we apply is to do the first everywhere and the second nowhere, except on links that show a problem in the first or that will carry something critical — the run between two floors, the one feeding the till, the one going to the busiest access point.
A low negotiated speed is the most useful signal of the testing day. A link negotiating below what the hardware at both ends allows almost always indicates an installation fault or a damaged socket, and in the large majority of cases it is fixed at the socket.
Label before understanding
People believe you have to understand an installation and then label it. It is the other way round: labelling is how you learn the installation.
The method requires no skill. One person moves from socket to socket with a two-part tester — the device costs the price of a meal — and another stays at the cabinet. Number the socket, find the port, write the same number at both ends.
The number has to be dull and positional: the room and a rank, not the name of whoever works there today nor the desk’s current function. People move from one office to another every year; walls do not.
Write on both ends and not only on the panel. Half the benefit is lost if the label exists only in the technical room, because the question you will ask in two years will be asked standing in front of a wall socket.
At the end of that day you have the one thing the original installer did not leave you: a plan. It fits on a sheet, it is accurate because it was verified socket by socket, and it is worth more than the certification report you will never have.
Dead sockets: how many, and why that is normal
Every take-over finds sockets that do not respond, and it is better to expect them than to read them as proof that everything must be redone.
The ordinary causes, by frequency: the cable was never connected at the cabinet — it exists, it arrives somewhere, nobody patched it. The socket has been torn out or painted over. The cable was cut during building work and both halves are in the wall.
The distinction that matters is between a socket dead at the cabinet and one dead in the wall. The first is fixed in five minutes with no building work; the second means pulling a cable, which is only possible if the route can be opened.
The two-part tester settles which without opening anything, and that is its main use: it says whether something arrives at the other end. A socket whose counterpart the tester cannot find is a dead or unpatched cable, and what follows is decided by the next section.
Set yourself a threshold before starting, because it prevents a decision taken in irritation. Below a fifth of sockets dead, repair case by case; above it, the question becomes whether to redo the zone.
The inherited patching, and what not to touch on day one
A taken-over cabinet almost always contains a tangle of patch leads whose logic nobody knows, and the temptation is to redo it all neatly on the first day.
Do not. As long as the installation is unlabelled, every lead unplugged is information destroyed: the correspondence between a port and a socket lived in that lead and nowhere else.
The correct order is photograph, label, draw the plan, and only then put the patching in order. Tidying then becomes trivial and risk-free, because every lead has a number at both ends.
One exception deserves handling on day one: leads that go nowhere and can be proved dead. Removing them reduces the volume and makes the rest legible, provided you have the proof — a tester, not an intuition.
Use the tidying to set the one rule that stops the disorder returning: a lead added is a lead labelled, on the day it is added. Without it the cabinet returns to what it was within eighteen months, and we have watched that happen to installations we tidied ourselves.
What makes a take-over impossible
Three discoveries turn a repair into a rewire, and they are sought before pricing anything.
The first is the closed route. A cable buried in concrete or run in a sealed conduit cannot be replaced: a new route is needed, which means building work. The companion article gives a whole section to saying the route must stay openable; here is where you find out whether it did.
The second is the full conduit. A conduit already holding three cables will not take a fourth, and you only learn that by trying. It is the discovery that derails the most quotations, because it is visible in no photograph.
The third is the inaccessible suspended ceiling, or the absence of one. An installation laid in a ceiling that was then closed up is, in practice, a frozen installation: what works works, and what does not cannot be repaired.
None of those three condemns the premises. They move the solution outside the walls — surface trunking, a wireless link between two zones — and these are acceptable answers, better chosen early than endured late.
Reuse or redo: the decision is taken by zone
Here is the decision that costs most when taken badly, and the usual error is taking it for the whole building.
Taken-over premises are almost always heterogeneous. One part was cabled properly at the outset, another was extended hastily when the previous business grew, and a third was improvised for some one-off reason. Those three parts are not worth the same.
So divide by zone — a floor, a wing, an open area — and decide zone by zone on three elements only: the proportion of dead sockets, the quality of the route, and what the zone carries.
A zone holding ordinary office desks with eighty per cent of its sockets live is kept, almost always. A zone that has to carry access points, cameras or the till deserves redoing even where it works, because the cost of a failure there is of a different kind.
A quotation proposing to redo everything deserves one simple question before signing: which zones could have been kept, and why were they not. A provider who has done that division answers in thirty seconds; one who has not is selling a rewire because it is simpler to price.
The lease decides more than the technology
There is nothing computing about this section and it regularly settles matters, in a country where most shops and offices are rented.
Embedded cabling is generally considered part of the premises and therefore the landlord’s, and that has two opposite consequences to hold together. You do not need permission to use what exists; you do need it to drill, seal or modify.
Put three questions before committing to anything, in writing: may I drill and fit trunking, what must I make good on leaving, and who pays if an existing cable turns out to be faulty.
The length of the lease changes the technical answer itself. Over three years, clean surface trunking is the right solution — reversible, no building work, removable. On a long lease or premises you own, embedded routing earns its cost because it will outlast three of your hardware renewals.
And keep in mind what you will not take with you. The companion article notes that cabling is the one IT purchase that lasts fifteen years; in rented premises those fifteen years partly belong to somebody else, which should be reflected in the amount you put into them.
Adding ten desks to an existing installation
The commonest case after a take-over is not failure, it is growth, and it goes better when the plan from section four exists.
The first question is not the cable but the cabinet: are there free ports on the switch, and free positions on the panel. That is often where things stop, and it is the cheapest constraint to lift.
The second is sockets per desk. The companion article gives the rule and it applies especially here: in an extension you run two sockets per desk because the cost is almost entirely in the travel and the opening up, not in the cable.
The third is grouping. Ten desks added in one place are handled by a conventional extension; ten desks added one at a time across ten rooms cost three times as much and justify considering a second distribution point rather than ten runs from the cabinet.
An extension is also the one moment when an original mistake can be corrected without paying for it twice. If the cabinet is badly placed — the companion article explains that this decides the rest — an extension is when a second enclosure gets added, not afterwards.
What to write for the next person
You have just spent two days reconstructing what the previous installer did not leave. The obvious conclusion is not to put whoever comes after you through the same thing.
The file fits in a folder and needs no software: the socket-by-socket plan from section four, photographs of the cabinet before and after, the list of dead sockets with their cause, and the division into zones with the decision taken on each.
Add the thing most often missing and most expensive to rediscover: where the routes run, and which of them can be opened. A freehand sketch on a sheet is enough and nobody else will do it.
Keep that file where it will survive — which is not only in the cabinet. A copy with you, a copy with the premises’ documents. A file left in the enclosure disappears at the first change of provider, which is precisely the situation that produced this article.
The file has a secondary value businesses discover when they leave: it passes to the landlord or the incoming tenant, and it turns anonymous premises into documented premises. It is the only item on this list that earns money rather than saving it.
What we do, and what we refuse
What we do is short and it transfers. We do the day of testing and labelling with somebody of yours — two people, one at the sockets and one at the cabinet — we build the plan and the division into zones, and we hand over the file from the previous section.
We refuse to certify an installation we did not lay without having opened the ceiling or the trunking. A certification report covers links whose route is known; producing one on an installation whose route is unknown means measuring something true and drawing a conclusion that is not.
We also refuse to price a full rewire where one or two zones would do. It is the easiest quotation to produce and the easiest to get accepted, because nobody argues with a safety argument — and it is the one that charges fifteen years of new cabling for a badly patched cabinet and six unconnected sockets.
And there is one thing to do this week without us, for the price of a meal: buy a two-part tester and walk your sockets one afternoon with a colleague. You will know how many are dead, and that is the only figure the rest of this article depends on.
Frequently asked questions
Can we tell what category existing cabling is?
The marking is on the sheath and can be read wherever a length of cable is visible — in the cabinet, behind a removed socket. But it says what was bought, not how it was installed, and the companion article explains that installation decides more than category does. A good-category cable badly installed performs worse than an ordinary one installed correctly.
Should a taken-over installation be certified?
Not everywhere, and it is an expense that sells easily. Do the laptop testing day on every socket — that answers "what works today" — and reserve certification for links that show a problem or that carry something critical: a run between floors, the till, the busiest access point.
Where do we start in a disordered cabinet?
With a photograph, and certainly not with tidying. While nothing is labelled, every lead unplugged destroys information: the correspondence between a port and a socket lives only in that lead. The order is photograph, label, draw the plan, then tidy — and the tidying is then risk-free.
How many dead sockets is normal?
There are always some, and the commonest cause is not a cut cable: it is a cable never connected at the cabinet. Set a threshold before starting so you do not decide in irritation — below a fifth, repair case by case; above it, the question becomes whether to redo the zone.
Does everything need redoing?
The decision is taken by zone, never for the building. Taken-over premises are heterogeneous: one part cabled properly, another extended hastily, a third improvised. Ask any full-rewire quotation which zones could have been kept and why they were not — a provider who has done the division answers in thirty seconds.
What does the lease say about cabling?
Embedded cabling is generally part of the premises and therefore the landlord’s: you may use what exists without asking, but drilling, sealing or modifying needs permission. Put three questions in writing before committing — the right to drill, what must be made good on leaving, and who pays if an existing cable proves faulty.
Where we come in
A two-box tester costs what a meal costs and tells you in one afternoon how many outlets are lying. What it does not show is what happens above the false ceiling.
- We run the labelling day with somebody from your team, never instead of them.
- We open the ceiling before writing a line about the state of the install.
- We price zone by zone, and one zone is enough more often than people think.
If every outlet answers and carries a label, redo nothing: replacing cabling that works is the least profitable spend in this pillar.
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