There are lots of great reasons to want another storey on your house. Better views. More breeze. It frees up space on the ground floor without eating into the garden. Parents can have a bit of privacy from the kids but it’s not as cheap as you think.
So let’s say you want to put a parents retreat up there; it will be great. The floor area will be at least 40 square metres – about the same as a double garage plus a set of stairs.
But it’s not the cheapest option.
The problem is that for the builders to build it, they’ll end up building at least double the floor area because everything under the parents retreat has to be rebuilt as well.
Of course, there’s a new, higher roof, and walls. The roof was held up trusses, so they’ll have to go, and the existing ceiling with it. If you have a house from the ’50s or earlier, there will be timbers holding up the ceiling, but they’ll be too small and far apart to put a floor on. You’ll have to build a new floor. The existing wall framing wasn’t designed for the extra weight of a room, so the existing plasterboard on the walls will be removed and have extra posts added to hold up the floor. They probably would have needed to remove the existing plasterboard anyway to install the upper-level plumbing and electrical wiring and replace the plasterboard, which was damaged when the ceiling was removed. And then you have to connect up both floors by the stairwell. And the new lower floor will inevitably impact on the adjoining walls. Your renovation went from being 40 sqm to 90sqm
So you end up building a 2 storey piece of new house. It’s fiddly for the builders – time consuming and needs to be done carefully, so the cost per square metre is more than a new house. Add another say, 15%
Despite the extra expense, sometimes a second storey is justified.
If you have incredible views, then you will add lasting value.
If you have a small site and you can’t lose any more yard, adding a second floor can bring more light into the ground floor and open up the street level. Great idea for urban terrace houses
If your ground conditions are bad –perhaps you’re in a flood zone- then the only way is up.
If the lower level needs to be renovated anyway, then the extra 15% is offset by the improvement in the ground floor views out into the garden. It adds value.
But is it cheap? No.