Advice · 4 min read · Updated 6 November 2026
New office rooms: lighting, air con and fire alarm mistakes to avoid
Why services matter as much as the walls
An open-plan floor is designed with lighting, heating, cooling, ventilation, fire detection and sprinklers spread evenly across a large space. As soon as you enclose part of it, those systems may no longer cover the new rooms properly. The partition itself might be quick and inexpensive, but fixing an overheating meeting room, an alarm that cannot be heard or a sprinkler obstruction after handover can cost more than the wall did.
Mistake 1: no fire detection or alarm in new rooms
Under BS 5839-1, the code of practice for fire detection and alarm systems in non-domestic buildings, the level of detection depends on the category of system in the building. In many offices, enclosed rooms need their own detectors, and sounders or beacons must be audible or visible inside them. Adding rooms without updating the system can leave areas uncovered. Ask the fire alarm maintainer to review the layout and update the zone plan. The building's fire risk assessment also needs updating under the Regulatory Reform (Fire Safety) Order 2005.
Mistake 2: blocking sprinklers and emergency lighting
- New walls built close to sprinkler heads can obstruct the spray pattern and may require heads to be moved or added
- Rooms built under a sprinklered ceiling usually need at least one head inside, designed by a sprinkler specialist
- Emergency lighting must still light escape routes and, under BS 5266-1, some rooms and areas need their own emergency luminaires
- Exit signs may need moving so they stay visible along the new escape route
Always check with the landlord or building manager, as sprinkler and alarm systems are often landlord-controlled in multi-let buildings.
Mistake 3: hot, stuffy meeting rooms
Meeting rooms fill with people, laptops and screens, so they gain heat quickly. If a room ends up with no air conditioning outlet, or a partition runs underneath a fan coil unit so it serves two rooms, the room will overheat. Approved Document F guidance for offices is commonly based on about 10 litres of fresh air per second per person, and HSE encourages carbon dioxide monitors to spot poor ventilation.
| Problem | Typical fix |
|---|---|
| Room has no supply air | Extend ductwork or add a new grille from the existing system |
| Partition under an air con unit | Move the unit or partition, or fit a separate unit |
| Room hot even with air con | Upgrade cooling capacity or add a local unit |
| Stuffy room, high CO2 | Add ducted fresh air or transfer grilles, sized to keep acoustic performance |
| Temperature controlled from another room | Re-zone controls or add a local controller |
Mistake 4: lights, switches and power in the wrong place
Partitions often cut across existing light fittings, leaving half a fitting in each room, or put a room on a lighting circuit switched from the open-plan area. Plan to reposition fittings, add switches or presence detection in each room, and set the lighting to suit screens. Floor boxes and power and data outlets need to be in the right place for the table and the screen. If the office has a raised access floor, decide whether partitions sit on the floor tiles or go down to the slab, as this affects acoustics, fire stopping and later changes.
Mistake 5: forgetting the ceiling void
Many partitions stop at the suspended ceiling. That is quick and cheap, but sound, smoke and air can then pass over the top through the void. Acoustic rooms usually need the partition taken up to the slab or a barrier built in the void, and fire-rated partitions must have fire stopping above the ceiling to maintain their rating. Any gap left for ducts or cables needs to be sealed with the right product.
Who is responsible for compliance
Since 1 October 2023, the Building Regulations in England have included dutyholder duties introduced by the Building Safety Act 2022. Clients, designers and contractors each have responsibilities, and where more than one contractor is involved the client should appoint a principal designer and principal contractor for building regulations purposes. The Construction (Design and Management) Regulations 2015 also apply to fit-out work, with notification to HSE required if a project lasts more than 30 working days with more than 20 workers on site at any one time, or exceeds 500 person days.
- Appoint someone to coordinate partitions, electrics, mechanical services and fire systems
- Ask for marked-up drawings showing services changes before work starts
- Get the fire alarm and emergency lighting certificates updated at handover
- Update the fire risk assessment and keep everything in the building file
Frequently asked questions
Does every new office room need a smoke detector?
It depends on the category of fire alarm system in the building and its design under BS 5839-1. In many office systems, enclosed rooms need their own detector, and every area needs to be able to hear or see the alarm. Ask your fire alarm maintainer or designer to review the new layout before the partitions go in.
Can partitions be built under existing air conditioning?
They can, but a partition should not split an indoor unit or diffuser between two rooms, and each room needs adequate supply air and temperature control. Often units are moved, ductwork extended or a separate unit fitted. Plan this with a mechanical contractor at the design stage, because rearranging it after the wall is up costs more.
Do I need my landlord's permission to alter sprinklers and fire alarms?
Usually yes. In multi-let buildings, sprinkler, fire alarm and building management systems are often owned and maintained by the landlord, and leases normally require consent for alterations. The landlord may insist that their own contractors carry out the work. Include these changes in your licence for alterations application.
fit-out HVAC fire alarm common mistakes
