Installing or keeping a boiler in a kitchen cupboard is perfectly legal — but there are ventilation and clearance requirements that must be met.
Minimum clearances
The boiler manufacturer specifies minimum clearances in their installation instructions. Typically: 150mm sides, 150mm top, 500mm front. The cupboard must allow these clearances to be maintained.
Ventilation requirements
Room-sealed (fan flued) boilers take combustion air from outside via the flue — they don't need the cupboard to be ventilated. Open-flued boilers (rare in modern installations) require specific ventilation openings — these should not be installed in a cupboard.
Flue route
The flue must exit to outside in the shortest practical route. Through the back of the cupboard and through the kitchen wall is usually the most straightforward. The flue terminal must be correctly positioned away from windows, doors, and air intakes.
Access for servicing
The engineer must be able to access all service points — the front of the boiler, the condensate trap, the magnetic filter, and the gas valve. A door that can be fully opened is essential.
Fire safety
Cupboard interior surfaces near the boiler should be non-combustible or lined with suitable material. Our installation team will assess and advise on any required modifications.