Network installation for new buildings: what to plan before construction starts

Why infrastructure decisions can't be retrofitted cheaply

Network infrastructure is a first-fix trade. Cable routes, containment, conduit and core penetrations all need to go in before plastering, floor finishes and suspended ceilings are completed. When they don't – because nobody commissioned a network design until fit-out, or because the cabling contractor was appointed after practical completion – the building has to be opened back up.

That means cutting into finished walls, lifting floors, removing ceiling tiles and making good afterwards. On a commercial build, remedial work of this kind rarely costs less than two to three times what it would have cost to do it right at first fix. On a large hotel or mixed-use development, the figure can be significantly higher.

The other cost is time. Retrofit cabling work competes with finishing trades and handover programmes. It creates snagging, it delays occupancy and it often results in compromised installations – cable routes that aren't ideal because the ideal route is no longer accessible, or containment that's undersized because there wasn't space to install anything larger.

The fundamental problem is that network infrastructure is often treated as an afterthought in the procurement chain. It doesn't appear on architects' drawings by default. M&E (mechanical and electrical) consultants don't always scope it. And contractors don't always ask whether it's been commissioned. By the time someone does ask, the building is already half-built.

What a structured cabling design involves

A structured cabling design starts with understanding how the building will be used. Different use cases drive different requirements: a hotel needs a cable outlet in every bedroom plus back-of-house runs for access control, CCTV and hospitality systems; a commercial office needs dense outlet coverage across open floors with capacity for flexible desk arrangements; a mixed-use building needs both, served from a single coherent infrastructure.

From that use-case analysis, a network design will specify the cabling standard, the outlet density, the cable routes and the locations of the distribution equipment. For horizontal cabling – the runs from patch panels to individual outlets – Cat6A is the current standard. It supports 10 Gigabit Ethernet at full channel lengths, and it's the baseline that any credible installation should be designed to. Cat5e is obsolete for new builds; Cat6 is acceptable but Cat6A is the more future-proof choice given the cost differential is modest at design stage.

For vertical or backbone runs – the connections between floors and between distribution points – multimode or single-mode fibre is standard. Fibre carries higher bandwidth over longer distances with no electromagnetic interference, and it's the right choice for any inter-cabinet run of meaningful length.

The design will also specify the structured cabling system supplier or standard – many contractors work within a specific manufacturer's system such as CommScope, Panduit or Brand-Rex, which provides end-to-end product warranties on certified installations.

Comms room and MDF/IDF placement

Every building needs at least one comms room. On a single-floor building, that's typically one Main Distribution Frame (MDF) – the primary termination point for external connectivity and the heart of the internal network. On multi-storey buildings, the MDF is usually supplemented by Intermediate Distribution Frames (IDFs) on each floor or zone, connected back to the MDF via fibre backbone.

The MDF is where the building's internet connection terminates, where core switching and routing equipment lives and where all building systems – network, CCTV, access control, building management – can be consolidated. Getting its location right matters enormously. It needs to be accessible to the incoming fibre or copper connection from the street. It needs to be central enough to keep horizontal cable runs within the 90-metre limit (the maximum channel length for copper structured cabling). And it needs to be in a location that doesn't compromise fire compartmentation or operational workflow.

IDF rooms on upper floors serve the same function locally: they receive the backbone from the MDF and distribute horizontal cabling to outlets across that floor or zone. Their placement follows the same logic – central to the area they serve, within 90 metres of the furthest outlet, accessible for maintenance.

These decisions can't be made independently of the architect and structural engineer. The comms room needs power, dedicated cooling (or at minimum adequate ventilation), a stable floor load rating and often its own fire compartment. It needs to appear on the architectural drawings and be coordinated with every other trade that touches that space. If that coordination doesn't happen at design stage, the room ends up too small, in the wrong location, or fitted with a fire suppression system that wasn't designed for an active equipment environment.

Power and cooling requirements

Network equipment generates heat, and it draws power continuously. Both need to be planned for in advance.

The MDF room will typically house core switching, patch panels, UPS (uninterruptible power supply) equipment and potentially a server rack if the building has any local compute. That equipment needs dedicated power circuits – not shared with general building loads – with sufficient amperage for current equipment and headroom for future growth. It's not unusual for a medium-sized building's MDF to require a 32A three-phase supply as a minimum; larger deployments need more.

Cooling matters because switching equipment can't operate above defined temperature thresholds. A sealed room with no dedicated cooling will overheat in summer, and overheating equipment fails. The cooling requirement needs to be specified early and coordinated with the M&E consultant so it's included in the building's mechanical services design – not bolted on afterwards as a portable air conditioning unit wedged against the door.

IDF rooms on individual floors are smaller and typically require less power, but they still need their own dedicated circuits and at minimum passive ventilation. This all needs to go on the M&E drawings at design stage.

Cable containment and fire barriers

Containment – the trunking, conduit and cable trays that carry structured cabling through the building – is one of the most commonly undersized elements of a network installation. The reason is straightforward: containment is often sized to the current cable schedule, with no allowance for future growth. A building that opens with 50% of its cable capacity used can't easily add more runs five years later if the containment is already full.

Good practice is to design containment at 40–50% fill at day one, leaving the remainder for future cabling. In practice this means specifying containment that looks oversized relative to the initial installation. It isn't – it's correctly sized. A 150mm trunking run that carries 30 cables today has room for another 30 tomorrow without any building work.

Where cabling passes through fire compartment boundaries – walls, floors or ceilings that form part of the building's passive fire protection – it must be fire-stopped. This means fitting intumescent seals around cable penetrations: materials that expand when heated to seal the gap around a cable bundle and prevent fire and smoke spreading between compartments.

This is a legal requirement under Building Regulations in the UK, not optional best practice. Fire stopping must be installed by a competent person and documented. On new builds, this is normally inspected by the building control body as part of sign-off. If it's been missed or done poorly, it becomes a significant remedial item at practical completion – or worse, it remains undetected until a fire safety audit years later.

Working with architects and M&E consultants

The structured cabling design needs to exist as a formal set of drawings, not just a specification document. Cable routes need to appear on floor plans, comms room layouts need to be drawn, and containment routes need to be coordinated with ductwork, pipework and ceiling void restrictions.

That coordination is what makes the difference between an installation that goes in cleanly and one that involves daily renegotiation on site. The M&E consultant needs to know where the containment runs so they don't route ductwork through the same void. The architect needs to know where the comms rooms are so they're allocated correctly on the drawings and don't get reallocated to storage. The structural engineer needs to know about any core penetrations so they can be designed properly.

We provide CAD drawings of structured cabling designs as a standard part of our process. That means there's a set of documents that can be issued to the project team, reviewed, coordinated and updated through the design and construction phases. Without those drawings, the network installation exists only as a trade contractor's programme – invisible to everyone else on the project until problems emerge on site.

The right time to appoint a network infrastructure specialist is at RIBA Stage 3 or Stage 4 at the latest. By Stage 5, you're on site and the window for design-stage coordination has closed.

The commissioning and handover process

Installing the cabling is not the same as commissioning it. A cable that's been nicked by a screw, kinked around a corner or terminated badly will pass a visual inspection and fail under load. The only way to know that every cable run performs to specification is to test it.

Industry-standard commissioning uses a cable certifier – a FLUKE DSX or equivalent – to run a full suite of tests on every copper link: wiremap, insertion loss, return loss, NEXT (near-end crosstalk) and the other parameters defined in ISO/IEC 11801 and TIA-568. Each run either passes or fails against the specification. Fails are investigated and rectified before handover.

The output is a certification report: a record of every outlet tested, every result achieved and every pass/fail. That report is part of the building's as-built documentation and should be handed over to the building owner alongside the O&M manuals. It provides the baseline against which any future performance issues can be investigated, and it's the only way to know whether you've received what you paid for.

Fibre runs should be tested with an OTDR (optical time-domain reflectometer) to verify loss levels and confirm there are no faults in the run. Again, the results should be documented and included in the handover pack.

The mistakes that cost developers most

The same problems appear on project after project. They're not difficult to avoid – they just require the right decisions to be made at the right time.

Appointing the cabling contractor too late. A contractor appointed at first-fix stage with no prior design input will produce an installation that wasn't coordinated with the rest of the project. The result is containment routes that conflict with ductwork, comms rooms that are too small and cable lengths that exceed specification because the routes aren't what they should have been.

Undersizing containment. Trunking and conduit that's full on day one is a problem that compounds over time. Every future change – an extra outlet, a new system, a technology upgrade – becomes a major project rather than a minor addition.

Failing to coordinate comms room requirements with M&E. A comms room without adequate power or cooling will either fail or require expensive remedial work. Both are avoidable.

Skipping cable certification. Uncertified cabling is a liability. You don't know what you have, and when something goes wrong – and something always does eventually – you have no baseline to work from.

Ignoring fire stopping. This is a compliance issue, not just a practical one. Cables passing through fire compartments without intumescent seals are a regulatory failure that needs to be remedied, regardless of what it costs.