Where in my house is it safe to install a boiler?

You can have your boiler installed safely in most rooms, or even the loft. There are, however a few things to consider:
Your boiler should be installed inside a building and can be fitted to any suitable wall strong enough to take its weight when full of water.
The boiler’s flue must be able to pass to the outside, either through an outside wall or through the roof. The boiler installation manual gives the minimum legal distances the flue terminal must be from windows, air bricks, other buildings etc, to comply with Building Regulations.
As well as the flue, you must consider where to fit the condensate pipe that takes away the liquid that condenses as the gases cool inside the boiler. We recommended that this pipe discharges internally into the household drainage system. If the condensate pipe is fitted outside, it could freeze during cold weather and make the boiler shut down.
If you decide to have it fitted in a garage or outhouse, we recommend you get additional frost protection fitted to protect the system pipework, even if the boiler has its own frost protection.
When positioning the boiler, you must allow sufficient clearances and access for servicing. Please check the installation instructions for details.
The boiler may be fitted inside a cupboard without having air vents. Modern boilers are room sealed and will run sufficiently cool without ventilation.
If the boiler is fitted in a bathroom or shower room, please refer to the current Wiring Regulations and Building Regulations, which explain the different zones in the bathroom where it is safe to install and boiler, and where it is unsafe to do so (In GB this is the current I.E.E. Wiring Regulations and Building Regulations. In IE reference should be made to the current edition of I.S. 813 “Domestic Gas Installations” and the current ETCI rules)
If your house is a timber framed building, please refer to the current edition of Institute of Gas Engineers Publication IGE/UP/7 (Gas Installations in Timber Framed Housing)
If your boiler runs on LPG (Liquid Petroleum Gas), you should not have it installed in a basement or other position below ground. This is because LPG does not rise, and will therefore not be dispersed should there be a gas leak. This information should be used for guidance only. Your Gas Safe registered installer will be able to survey your home and tell you the most convenient, safest and legally compliant place for your boiler and discuss where the flue and condensate pipe should go.