In 350, a survey showed that Rome had only 1782 private houses. Most people rented an insula (‘island’) in one of the 46,602 apartment blocks. The buildings were divided vertically, because a property owner owned the land from the ground to the sky. Thus, a typical insula could be six storeys high, often with a shop on the ground floor. Despite the high rents, most insulae were not built or maintained to a high standard. The walls were made of mud and wattle, which cracked when it dried in the summer heat. The poor had no cooking facilities, and only a few buildings had shared latrines in the basement - the alternative was the public latrines.

Wealthy homes tended to be built in one basic style. The front door opened into an atrium with a pool in the middle of the floor and an opening to the sky. There would be a peristyle or colonnaded garden at the back. The house would have few windows, and walls would be made of plaster and painted in bright colours, leading to a high ceiling. A house in Silchester, for example, had panels of plain colour, mostly red and yellow. The panels did sometimes have patterns, such as veining or dots. The walls would often be bordered in a deeper colour. One wall had a black band below a dark red dado, with a green band above. On the red band, ears of yellow barley point towards lilac quatrefoils, and there are green circles with leaves jutting from them. It was also fashionable to paint walls with imitation marbling, painted pillars, garlands, candelabra and vegetables; nature was a popular theme.

Although Roman homes had surprisingly little furniture, the floors could be richly decorated with patterned marble, or sometimes mosaics. Once one neighbour laid a mosaic, the rest might copy the fashion. A mosaic reflected the artistic taste of the house’s owner, but also had practical value, providing an easily cleaned, bright surface.

Floors were made of brick, tiles, mortar, opus sigmium (white cement with highly polished, crushed brick) and tesserae. Designs may have been copied from pattern books, which the mosaic workers would compile using inspiration from Hellenistic sources. The workers used various materials to vary the colours: Purbeck marble gave black and blue tiles; chalk and limestone yielded cream, white and pink; sandstones and tiles gave red and brown. Red glass gives a vivid colour to the wounded Actaeon’s thigh at Cirencester.

The content of the mosaics gives us more to think about. One notable point is that Celtic mythology does not appear in mosaics, although it is portrayed in sculpture. Some mosaics showed scenes from everyday life: a cat catching a bird, for example, or hunting scenes. Many show scenes from mythology, and a story-teller might use the illustrations to recount his tales. In Hinton St Mary, one owner had a Christian theme portrayed. This owner might not have been Christian, but may simply have wanted to expand his knowledge. Another mosaic found in the same villa shows Bellerophon mounted on a Pegasus slaying the Chimaera, a victory of good over evil, whose death also brings forth life.

Wealthier Romans heated their homes in a very efficient manner. The heating came up from under the floor, by the use of hypocausts. Sometimes the floor was set with panels laid out in a union jack pattern. Other floors were placed on brick or tile pillars. In addition, box-tiles were internally plastered in rows going up the walls. A furnace, which was stoked from outside, heated the air in this system. The whole arrangement was not only efficient, but also prestigious enough to make neighbours want similar systems. It was probably an expensive system, because in many houses, it seems that only one room was heated this way. This also suggests that there would be one room for people to gather in on cold days.

A few houses even had a bath-suite added, an attraction comparable to a private swimming pool in one of today’s houses.

Less wealthy homes did not have a hypocaust; instead they would have a hearth on the floor with no real control over the smoke. In some of the villas there are recesses in the walls, which may have been chimneys. But the most popular method was the portable brazier. Houses in Silchester have burnt patches on the floors as evidence. But braziers were dangerous, not only because of the risk of burning the house down, but because the rooms were sealed against the cold, letting no air out and increasing the danger of carbon monoxide poisoning. Emperor Julian (361-3) nearly died this way, and Emperor Jovian (363-4) did die of it.

The insulae had no sanitation. Most people fetched their water in buckets, carrying them from public fountains in the streets. Still, the Roman system of water supply was not equalled by any other system until the 19th century. The backbone of the system was the aqueduct. From the aqueducts ran complex networks of lead piping; the system used gravity to channel the water. The waste would run away through the underground sewer system.

The water pump was really two simple pumps joined together. On each side was a piston raised by a rocking handle, which sucked water into a cylinder through a one-way valve. By pushing the piston down, the water was forced into the outlet pipe. The valve cover let water flow out, but if it tried to reverse back into the piston the cover would shut. From the outlet pipe the water ran out through another valve. The pistons alternated to send a jet out of the central pipe.

Another kind of fountain, like those used in Pompeii, worked by gravity. The weight of the water in a hidden tank forced a jet of water out from an outlet.

Bath-houses had their own water supplies, and so did public toilets. Public toilets consisted of several seats arranged in a row. The Romans used sponges on sticks instead of toilet paper.

Wealthier people often had mains water in their private houses, and also collected rainwater from the roof.