If its a 2.5 storey house, you shld refer to the level above the 2nd storey as the attic instead of the 3rd storey. It'll be less confusing for you tt way. To visually differentiate if its an attic or a proper 3rd floor,notice tt an attic will hv a side of the roof touching and joining the floor level. Walk around to see a few more houses n u'll soon spot the attics. Attic space and floor area can have many use ; bedrooms, gym,movie theatre, entertainment room, billiard and karaoke room, garden etc.... U can go to this URA link to find out what type of houses can be built in any landed zone : http://www.ura.gov.sg/uramaps/?config=config_preopen.xml&preopen=Master%20Plan Key in yr address and click GO. Next to GO button, click on URA MAPS. Then select "SPECIAL AND DETAILED CONTROL PLANS" in the URA MAPS box. Then select "LANDED HOUSING AREAS PLAN" U'll see what type of housing zone is yr house in ie 2 storey mixed landed, 3 storey mixed landed, 2 storey semi D, 2 storey bungalow, etc Attic is like a bonus level tt our gahment allows for landed house owners to extend their GFA. Some house owners utilise this bonus while others don't. Its optional. Hope its clearer to u now !