IT fit-out for commercial property conversions: a developer's guide

The commercial property conversion challenge

New builds start with a blank page. You specify the comms room location, the containment routes, the power feeds – everything gets designed in from the ground up and the construction programme accommodates it. Conversions don't offer that luxury. The existing structure constrains where cabling can run, where comms rooms can go and how much power is available. The fit-out team, M&E contractors and IT installer are all working within the same shell simultaneously, competing for space and access.

The other challenge is uncertainty. Until a thorough survey is done, nobody knows what's actually in the building. Cabling routes marked on old drawings may not reflect what was actually installed. A comms room shown on the as-built plan may have been repurposed. Power supplies may be inadequate. The first task in any conversion IT project is to establish what you're actually working with before committing to a specification.

Assessing existing infrastructure

Before any specification work begins, a survey of the existing infrastructure is essential. This isn't a desk exercise – it requires physical access to ceiling voids, comms rooms and containment routes throughout the building.

The survey should establish:

• What structured cabling is installed, and what standard it was installed to (Cat5, Cat5e, Cat6, coaxial, fibre)
• Where existing comms rooms are located, how large they are and what power supply they have
• The condition and capacity of existing cable containment – trunking, cable trays and conduit routes
• Whether existing fibre runs are still intact and what they connect
• The location and specification of any existing active equipment (switches, patch panels, UPS)
• Power availability to comms room locations, including whether additional circuits are needed

The survey output should be a written report with photographs and, where possible, updated floor plans showing what's actually installed. This becomes the baseline for all subsequent design decisions.

When to retain and when to replace

Not everything in an existing building needs to go. The retention vs. replacement decision should be based on objective testing, not assumptions.

Cat5e cabling installed in good condition and tested to current standards can often be re-used. The test is whether it passes FLUKE certification to the required category – Cat5e needs to pass Cat5e channel performance, Cat6 to Cat6 and so on. Cabling that passes certification is fit for purpose regardless of its age. Cabling that fails, or that was installed to Cat5 or below, should be replaced.

Fibre runs should be OTDR tested. Existing multimode fibre may be adequate for short backbone runs; longer runs or higher-bandwidth requirements may necessitate replacement with OS2 single-mode fibre even if the existing runs test as physically intact.

Containment is worth retaining where it has spare capacity and runs in the right directions for the new layout. Old containment that's full, in poor condition or running to locations that no longer make sense should be replaced or supplemented. Adding new trunking alongside existing routes is often more cost-effective than trying to re-use what's there.

Active equipment – switches, wireless controllers, patch panels – should almost always be replaced in a conversion project. Network switches have a finite lifespan, older equipment may not support current standards (PoE+, 2.5GbE, 10GbE uplinks) and second-hand warranty positions are difficult to establish. The cost of retaining aging active equipment and discovering failures during commissioning is invariably higher than replacing it upfront.

Structured cabling for conversions

Where new cabling is being installed, the specification should reflect current standards and the anticipated lifespan of the fit-out. Cat6A is the current recommended minimum for new horizontal cabling runs – it supports 10GbE to the desktop, provides adequate headroom for PoE power delivery and is backward-compatible with all earlier standards.

In a conversion project, cable routes are often less straightforward than in a new build. Structural elements – beams, columns, floor-to-ceiling masonry – create obstacles that require careful routing planning. The cable survey should identify practical routes before the design is finalised, and the design should be reviewed against the physical constraints of the building rather than drawn on a clean floor plan and assumed to be achievable.

Maximum horizontal cable run lengths apply in conversions just as in new builds: 90 metres for the permanent link, 100 metres for the full channel including patch leads. Buildings with deep floor plates or multiple floors without intermediate distribution frames need careful planning to stay within these limits without adding additional comms room locations.

Network equipment and active infrastructure

The active network equipment specification – core switch, distribution switches, access switches, UPS – should be sized for the building's anticipated occupancy and use, not for what was there before.

For commercial office conversions, PoE (Power over Ethernet) switch capacity is often underestimated. Access points, IP cameras, door controllers, VoIP phones and other PoE devices all draw from the switch's power budget. A building with a comprehensive wireless network, IP CCTV and access control can easily exceed the PoE budget of an undersized switch. The design should calculate the expected PoE load and specify switches with appropriate headroom.

Comms room UPS sizing should account for the full connected load at the point of failure – all active equipment, all PoE devices and any environmental monitoring. A runtime target of 15–30 minutes is typically sufficient for a controlled shutdown or generator start, but this should be confirmed with the client based on their operational requirements.

Wi-Fi design in challenging buildings

Wireless coverage in a conversion building is rarely straightforward. Thick concrete walls, steel-reinforced floors, metal suspended ceilings, structural columns and partitioned office layouts all affect RF signal propagation in ways that standard new-build WAP spacing assumptions don't account for.

A proper RF survey – using Ekahau Site Survey or equivalent – is essential for specifying WAP positions in a conversion. Predictive modelling tools require accurate floor plans with material types annotated; without that, the output is no more reliable than an educated guess. Where detailed building information isn't available, a physical walkthrough with a Wi-Fi analyser to understand existing signal attenuation is a worthwhile step before finalising the design.

Listed buildings present a particular challenge. Planning constraints may restrict the routing of new cables through walls or ceilings, limiting WAP placement options. In these cases, a higher WAP density with more carefully chosen positions – combined with 6GHz band capability for close-range high-density coverage – can compensate for the lack of optimal locations. DECT telephony and other wireless services benefit from the same survey process.

Security and access control

IP-based access control and CCTV systems share the structured cabling and network infrastructure with data and voice services, and their requirements need to be factored into the IT design from the outset rather than treated as an afterthought.

Access control door controllers, readers and locking hardware all require both data connectivity and power. Where PoE-powered door hardware is specified, the switch PoE budget needs to include these loads. High-security locks and electric strikes that require more power than PoE can deliver need separate power supplies factored into the M&E design – the IT and M&E teams need to coordinate on this early.

IP camera positions should be agreed with the security consultant and client before the IT cabling design is finalised, as each camera requires a dedicated outlet. Camera positions on upper floors or in areas remote from the main comms room may drive additional intermediate distribution points to keep runs within specification.

Coordinating IT with the fit-out programme

In a conversion project, IT infrastructure installation runs alongside M&E, fit-out and – in some cases – ongoing construction. The sequencing of IT works relative to other trades is critical and needs to be established at the programme stage, not discovered on site.

The critical path items for IT are:

• Comms room preparation: power feed, earthing, cooling and physical security need to be in place before active equipment can be installed. This is an M&E dependency and must be on the programme as a preceding activity
• Containment installation: cable trays, trunking and conduit routes need to be installed before ceiling and wall surfaces are finished. Once plasterboard is on and ceilings are closed, adding containment becomes expensive and disruptive
• Fibre backbone: inter-floor and inter-zone fibre runs should be pulled before vertical service risers are sealed and before floor finishes are laid in routes where floor-level containment is used
• Horizontal cabling: outlet cabling should be pulled before partitions are fully boarded and before ceiling tiles are fitted, but can follow containment installation by a short interval
• Active equipment installation and commissioning: this is a late-stage activity but needs access for testing before snag lists close – allow adequate time before practical completion

The IT installer should be attending site progress meetings and providing a two-week lookahead programme alongside other trades. Dependencies between IT and other contractors – M&E for power and cooling, joinery for comms room fitout, the main contractor for access to risers and roof spaces – need to be tracked actively rather than assumed to resolve themselves.