Chalet Bungalows are a great way to build and have to be more cost effective and definitely more attractive than a traditional 2 storey house provided you go with light structural materials using steel studs and thin Hardieflex on these second floor rooms, assuming that the roof has been done with steel roof trusses you will have a strong structure to attach to. Buildings in the Philippines tend to be done with CHB, but to extend them up to a second floor is more expensive than building on just one level, when I first heard this I found it hard to believe but now fully understand why this is the case. A Chalet Bungalow in an alternative, with a gabled rood style you can gain 66% of the house footprint in floor space, but a lot less with a hipped roof at around 33% a little more can be had in both cases if the interior of the upstairs rooms have coombe (slanted) ceilings. Wondering why attics are never turned into living accommodation in PH? the obvious answer to this has to be the heat under these Hot Tin Roofs, but not a difficult problem to solve, Imac uPVC roofing a plastic material that likely cuts down heat transfer by around 80 to 90% I know this as that is the material I used when building my house there, with a bit of added insulation to the walls and ceilings upstairs, this will perform much better than say a 2 storey house in CHB with big expanses of the walls heating up when direct sunlight hits them, insulation in PH is not a common material and sometimes difficult to find and when available it is expensive, another problem easily solved, Rice Hulls is the near perfect insulation material and meets building standard codes in many first world countries and the cheapest form of insulation you can get, maybe not if you live at the North Pole? The house I built in Valencia has been done to support this idea of turning it into a Chalet style complete with a PC stair for access, the roof trusses were also done with this in mind, I will attach a Pic of this and also one of a typical CB when complete.