Victorians used to build houses with back additions, a very flexible form of room arrangement which could be built with the minimum of excavation. The back addition could be above or below the rest of the house, according to slopes on the given the site.
This Collins house has floors at two levels as the ground was higher at the back than the front.
On the previous page is a cross section of one of the houses, built as it happens near the edge of the old fish pond. In this version the coal cellar is in the centre of the house, with the access from the side entrance. The front rooms are at one level and the rear ones are half a storey lower. This has allowed the architect to add a third storey at the rear and yet make the house look quite modest from the front. By lifting the top ceilings into the roof and rounding the top comers of the attic rooms, the normal roof space has been reduced to almost nothing. Many householders have considered putting an extra room in the roof, only to find that it is impossible as Collins has forestalled them and had already filled the roof space.