We are adding on a masterbedroom (WIR & bathroom) and study to our existing old house, and it is costing $150-160K. I was hoping it would be around $120K Max, but alas, things are expensive. We could actually knock the existing house down and build a new 4 x 2 for around probably $180K - so it is food for thought. But we would also need to find somewhere to live whilst it is being built. (more money) but we love our existing house, it is old, but it has high roofs, wood floors and is structurally sound, so hate to think of knocking it down. But we need the additional bedroom for one of the kids, going into highschool etc, so will need his own room etc. If you are looking at buying, don't forget to add the stampduty as well, as that can be a killer too. Decisions decisions.