I have suspended using Sketchup until more fundamental issues are resolved. It was a mistake to use Sketchup so early until the issue of affordability is addressed. We have a limited budget for building the house and hence I not not have license to design the house until the issue of costs are settled. Costs are primarily driven by square feet of the floor area of the house. Of course while building materials and even design (structure as well as interior) can affect the costs, the bottom line is still amount of floor space.
From discussions with several contractors and people who has built their own house (recently), the estimates would range from RM 80 to RM 120 per sq ft. After more detailed discussions it was agreed that any thing over RM 100 would be considered a luxurious house. And hence our focus should be around RM 80 to RM 90 per sq ft. That leaves us with a house less than 2,500 sq ft ! That is not actually the size that I was thinking of for a large family. In any case I now have a design constraint.
In addition, it was advised that to further reduce the cost of the house, I have to keep the structure light and the roofs simple.
So with hindsight, that should have been our first objective;
"Determine the constraints for the house design"