Roofs, and what each one is for.

The roof is the biggest single decision on a house that most people make in a minute. It decides the shape of every room under it, the height of the walls, where the sun comes in, and how the house does in wind, rain and snow. The Studio draws eight. Here is what each one is for.

Skillion

One plane, sloping one way. The tall wall is where the light and the sun come in, the low wall is where the eaves come down. Cheap to build, easy to keep watertight, and it puts a high window wherever you want one. Best where you want the house to look one way and be lit from the other: a view to the south and sun from the north, say.

Split skillion

Two skillions that meet at a step, usually with a high window in the step. The centre of the house gets light without a skylight, and the two halves of the plan can be different heights. A good answer for a long house that would otherwise be dark in the middle.

Flat

Not actually flat, but close to it, and the walls are the same height all the way round. The most modern-looking roof, and the easiest to draw a deep overhang on, which is what keeps it comfortable in a warm climate. It needs to be built carefully, because water does not leave a flat roof in a hurry.

Gable

The classic: two planes meeting at a ridge, with a triangle of wall at each end. The simplest roof to build and to insulate deeply, which is why it is the cold-climate roof. The gable end is where a big window goes for the winter sun. Steepen it and it carries snow.

Dutch gable

A gable with the top of the triangle hipped off. It has the gable's room inside and a little of the hip's shelter outside, and it looks like a house someone has cared about. Common on older Australian homes and on new ones that want to fit beside them.

Hip

All four sides slope to a ridge, no gable ends. This is the wind roof: nothing for a cyclone to catch, and every edge tied down. The Studio hips the roof by itself for a cyclonic town, unless you pick a different one yourself. It also carries eaves all the way round, which is what a hot dry house wants. The rooms under it have level ceilings.

Butterfly

Two skillions that fall towards the middle, so the roof is a V. The high walls are at the outside edges, which means big windows on both sides and a gutter down the middle. Dramatic, and it collects rain into one tank beautifully. Needs the middle gutter built well.

Sawtooth

A row of short skillions, each with a high window facing the same way. It lights a deep plan from above, all the way across, which is why it was a factory roof. On a house it makes a long, narrow block feel wide and bright.

Which one, then

If you are in cyclone country, hip. If you are in the snow, a steep gable. If you are on a hot dry block, hip or a wide flat roof for the eaves. If the view is one way and the sun the other, a skillion. If the block is long and narrow, sawtooth or a split skillion. And if you are not sure, the Studio will draw it with the roof it thinks fits and let you change your mind by tapping the word.