Retrofitting Security Technology in Existing Buildings: The Constraints

Key Takeaways

• In existing buildings, constraints determine the effort, not the system technology: unknown cable routes, occupied floor space and ongoing operations that cannot stop.
• Every cable penetration through fire-resistant building components must be fire-stopped; cables for fire alarm systems may, depending on the requirement, need at least 30 minutes of circuit integrity under the MLAR.
• Constraints of the existing building belong in the specification of services, otherwise they return in the project as change orders.
• A neutral review of existing systems and contracts avoids dependence on a manufacturer and creates comparability for the tender.

Why retrofitting an existing building differs from new-build planning

Anyone planning a fire alarm or intrusion detection system, video surveillance or an access control system in a new building starts with a largely unobstructed site. Cable routes can be chosen, fire compartments are created together with the structure, and the later use is fixed before planning begins. In an existing building this relationship is reversed: floor space is occupied, cable routes already exist, and operations continue. The constraints are given, and planning has to take them into account instead of setting them.

The system technology itself hardly differs. Detectors, cameras, door readers and control panels for intrusion detection systems, video surveillance and access control are the same components in new and existing buildings. The planning driver is not the technology, but the constraint under which it has to be installed:

Typical triggers for a retrofit are a modernisation backlog, official requirements, changes of use and legacy systems whose technology has reached the end of its service life. An intrusion detection system modernisation therefore rarely starts with the question of the right detector, but with the question of which routes, shafts and fire stops the building permits at all.

The more trades work on the same cable routes and fire compartments, the more decisive independent coordination across all parties becomes – a role that, in existing buildings, the operator's security department frequently delegates to specialised, manufacturer-independent specialist planning.

What must be known before planning

Every retrofit begins with an as-is survey and a needs analysis, before the target concept and detailed planning follow. This sequence corresponds to the planning steps that manufacturer-independent specialist planning follows from the first site inspection to acceptance. In an existing building, it decides whether the later specification of services is sound or whether unknowns return as change orders.

1. Document review: check installer drawings, as-built documents, logbooks, maintenance records and acceptance certificates for completeness and currency.
2. On-site inspection: record existing cable routes, installation shafts and distribution rooms, assess legacy systems and their condition, and note structural changes compared with the original planning status.
3. Evaluation: document deviations from the relevant standards and from the original concept, and bring them together in a report with concrete recommendations.

The document review deserves particular attention, because missing or outdated documents are the rule in existing buildings, not the exception. Conversions, changes of use and technical ageing mean that the documented planning status and the actual condition of the system can drift apart. A structured as-is survey creates transparency here before the first tender item is worded, and at the same time provides the basis for demonstrating operator obligations to the authority and the insurer.

Alongside the technical survey comes the needs analysis: which protection objectives apply to the property, which areas need which level of surveillance, and which insurer requirements and requirements for police connection apply in addition? The upstream threat and risk analysis provides the target concept against which detailed planning and the later tender must be measured. Only on this basis can it be judged which existing systems should be retained, extended or replaced.

Interventions in fire compartments, escape and rescue routes

This is where security technology meets structural fire protection. New cables for fire alarm and intrusion detection systems, video surveillance and access control have to be routed through walls, ceilings and shafts that, in an existing building, already have a defined fire resistance. Every retrofitted penetration is therefore not a purely electrical task, but an intervention in a building component whose protective effect must be preserved. Under § 40 MBO, cables may only be routed through room-enclosing components if fire spread is not to be feared for a sufficient period or precautions against it have been taken; the Model Cable Installations Directive (MLAR) specifies this requirement^[1].

Circuit integrity deserves particular attention in existing buildings. Electrical cable installations for safety systems required by building law, including fire alarm systems and their alarm components, must remain functional for a sufficient period in the event of fire; this is demonstrated via DIN 4102-12 with the classes E30 to E90, i.e. 30 to 90 minutes^[1]. Not every existing cable route may therefore be reused for new cables, and distribution boards need a correspondingly protected location. Both can only be planned reliably with a survey of the existing routes and fire stops, as the planning of fire alarm systems, fire suppression systems and voice alarm^[2] also requires.

Because each of these measures affects structural fire protection, coordination with the fire alarm and alarm concept and with the fire protection authority is required before the first opening is fixed. With access control systems, the interplay with escape routes comes on top: door functions that must be released in an alarm must not restrict the use of rescue routes in the event of fire. This coordination is a prerequisite for a legally compliant retrofit and belongs in the planning phase, not in the execution.

Building without stopping operations

The second major difference from a new build is a matter of time: operations continue while construction is under way. Whether a video system has grown old or an access control system is to be extended – from the planning perspective, ongoing operations are not a side note but a technical requirement that can be translated into construction phases, switchover dates and substitute measures.

1. Divide the building into phases: retrofit floor by floor or zone by zone, aligned with the use and occupancy patterns of the property.
2. Fix switchover dates: work on control panels, distribution boards and handover points outside core usage times, with defined test and rollback windows.
3. Plan temporary arrangements: temporary surveillance, manual access control and organisational compensation for the duration of each switchover phase.
4. Accept each phase: partial acceptances after each construction section, so that the protection objectives remain demonstrably in place throughout the construction period.

Temporary arrangements are not a defect, but plannable variables. While a secured area is being switched over, its surveillance function must be maintained, for example by temporary cameras, more frequent patrols or temporarily manual access control. Which substitute measure is permissible depends on the insurer's requirements and, where there is a police connection, on the requirements of the responsible body. These questions belong in the planning and then in the specification of services, not in the execution.

For critical infrastructure and ongoing production processes, business continuity is a protection condition, not an option. For operators of critical infrastructure, physical security is part of the overall concept of the facility anyway; a retrofit that interrupts operations would violate its own protection objective. Here, phase planning decides on feasibility, security and cost alike.

Trade interfaces: where projects in existing buildings typically fail

When retrofit projects fail, it is rarely because of the system technology, but because of the interfaces between the parties involved. Three of them determine the course and the outcome in practice.

The second interface is the one with the installer of the legacy system. Existing fire alarm, intrusion detection and access control systems are often tied to one manufacturer; extensions and spare parts then run through the same provider without any comparison taking place. A neutral review of the existing systems and contracts creates the basis for a manufacturer-independent tender here, because the modernisation and optimisation of existing systems is expressly one of the tasks of independent specialist planning.

The third interface is organisational. Access control systems process personal data; their planning and operation must comply with data protection law and are generally subject to co-determination. Video surveillance adds storage limitation, notification obligations and deletion concepts, which must already be taken into account in the planning phase. Whoever involves these parties only after the award risks delays that can no longer be made up during construction.

What this means for the tender and award

Constraints that are not described before the award return as change orders. The specification of services for a retrofit must therefore contain the conditions of the building as items that can be contracted, not as the bidder's tacit assumption. Four items should be firmly anchored in it:

1. As-is survey as a separate item: commission the document review and on-site inspection before detailed planning, including documentation of all cable routes.
2. Show fire stops: cable penetrations through fire compartments as separate items, with reference to the required fire resistance.
3. Describe operating times and phases: usable time windows, restricted areas and the substitute measures required per construction phase.
4. Make temporary arrangements contractable: temporary surveillance and manual access control as a service with a start and end date.

Having a retrofit in an existing building planned: manufacturer-independent specialist planning

Four decision factors determine the effort and cost of a retrofit long before the first installer submits an offer:

• As-is survey: the documentation, cable routes and condition of legacy systems are clarified before detailed planning.
• Fire compartments: every cable penetration is planned as a fire-protection-relevant intervention with fire stopping and circuit integrity.
• Business continuity: construction phases, switchover dates and temporary arrangements are fixed as contractable items.
• Depth of the tender: the constraints of the existing building, the status of standards and the evaluation criteria are fully anchored in the specification of services.

This is exactly where specialist planning for fire alarm and intrusion detection systems, video surveillance & access control comes in. It covers conception and detailed planning to DIN and VdS rules, including the requirements for police connection, as well as the neutral review, modernisation and optimisation of existing systems, from the as-is survey through the tender to acceptance. Because the planning remains manufacturer- and provider-independent, the constraints of your building decide on the system, not the interests of a provider.

Contact us for a no-obligation initial consultation. PLANATEL®: Independent planning and consulting since 1992. Tel: 040 / 23 73 02-30 | Email: info@planatel.de

Frequently Asked Questions

What must be considered when retrofitting access control in an existing building?

Access control systems must correspond with the building's fire protection and escape route concept. In existing buildings, cable routes and door conditions are often undocumented and must first be recorded in an as-is survey. Access control systems also process personal data and are generally subject to co-determination, so data protection and the works council must be involved early.

Can a fire alarm system be modernised during ongoing operations?

Yes, usually floor by floor or zone by zone, with defined switchover dates, temporary arrangements and organisational substitute measures. The prerequisite is phase planning that takes the use of the building into account. For fire alarm systems required by building law, coordination with the fire protection authority and the fire brigade is part of the planning to DIN 14675.

Which standards apply when retrofitting intrusion detection systems?

The basis is the DIN and VdS rules, in particular VdS 2311 for the planning and installation of intrusion detection systems. The edition VdS 2311:2025-06 has applied since 1 June 2025 and is binding from 1 January 2026 without a transition period. Insurer requirements and the requirements for police connection come on top.

Why are cable routes a planning topic of their own in existing buildings?

Every cable penetration through fire-resistant walls and ceilings is relevant to fire protection and must be properly fire-stopped. Cables for fire alarm systems may need to remain functional for at least 30 minutes in the event of fire. In existing buildings, ducts, shafts and fire stops are often undocumented and must be surveyed before planning.

What happens to legacy systems and existing maintenance contracts?

Existing systems and contracts should be reviewed neutrally before the retrofit, with no interest in a particular product. This makes it possible to establish whether an extension, a modernisation or a new installation makes economic sense. When optimising existing maintenance and servicing contracts, remuneration can also be success-based.

Who may plan fire alarm systems in existing buildings?

DIN 14675 applies to the planning and design (Planung and Projektierung) of fire alarm systems. PLANATEL® is certified to DIN 14675 for the phases Planung and Projektierung; assembly, installation and maintenance are expressly not part of the scope of services and are carried out by installers.

What does it cost to retrofit security technology in an existing building?

Concrete euro amounts can only be given reliably after the as-is survey, because in existing buildings constraints such as cable routes, fire stops, operating times and temporary arrangements determine the effort. A structured needs analysis and target concept before the tender lowers the risk of budget overruns and change orders.

Sources

1. Leitungsanlagen – Brandschutz – BauNetz Wissen
2. Brandmeldeanlagen, Löschanlagen & Sprachalarm – planatel.de