iron age real estate

Double-wall masonry is sometimes thought of as cheap, because it uses fewer bricks for wall area, but it can be quite strong, since the walls are usually connected at intervals with a tie-stone that spans both walls. My first lesson in the durability of double-wall masonry was during additions to a building by idiosyncratic engineer-builder, Carr Jones. What? Masonry, in earthquake territory? Garden-variety double-wall construction is referred to as rat-trap masonry, a bond popular for its insulating properties and economy of materials. Jones' California walls used steel ties, and his early 20c. homes are real estate manna. Pictured above is one example of the QUEEN of double-wall masonry, unique to Scotland: the broch. They're dry masonry: no mortar. They take the idea of tie stones and insulating cavities to another level! Given the severity of Scotland's environment, one appreciates the need for insulation, but the cavities in broch walls are unusual enough to provoke speculation about additional functionality. To get an idea of the technical sophistication of these dry-stone, iron-age structures, check out this trailer for a recent broch-umentary.