I'm about to install a fire alarm system in a two storey house which will be let as a single dwelling. In Electricians guide to fire detection and alarm systems it has table 5.4 specifiying which grade to use. The old tenant has moved out and the landlord has decided to spruce it up, new bathroom, new kitchen, knock a few walls and some electrical work. Does that make it a 'Materially altered dwelling'. If so it would mean adding another optical in the living or dining room and a heat detector in the kitchen. What would you guys put in? Cheers