In the twenties and thirties, these cube-shaped buildings were quite popular and were affectionately nicknamed the "coffee mills" as they reminded people of the boxy manual coffee grinders typical of that period. The two-floor, compact, cube-like house was cost-effective to build and the steep hipped roof offered plenty of headroom for the inexpensive loft conversion at a later date. In other words, builders got a lot of floor space for very little money. The architect Philippe Frey describes how cost-efficient construction was a key theme of the time: "Only the outer walls are solid masonry. They were built with tiles and stones, anything people could use. Therefore, the masonry is very mixed and quite instable statically". For this reason, for example, the installation of larger windows would have been very difficult and expensive. "But that was not a problem for any of us", says the architect.