A new house design becomes popular in the 90s. Called "Tuscan", it dispenses with the overhanging eaves. That means you can build exterior walls closer to boundaries – and thus get more house on a small block.

As a result of their being no overhanging eaves, the houses leak. In any sort of rain, water gets in and runs down walls. Eventually the local government changes the rules to mandate eaves (and thereby admitting they’d been wrong in the first place).