Steel I-beams would be common for low rise urban and large suburb/rural mansions. Another possibility, although not very common, was to span openings with specialty blocks formed into shapes to create a "flat arch". The illustration below shows 2 skewbacks, 4 fillers and the key-block.Click to Enlarge 15.5 KB Not that I've seen. There are three types of terra cotta blocks - dense, semi-porous and porous. Exterior walls are usually dense, thus are the most brittle. Semi-porous are usually made with the clay mixed with coal dust. These were typically made for fireproofing, not structural purposes. Porous blocks were made with sawdust that burned off when firing. These were typically used for interior, non-load partitions. Occasionally, porous blocks were strategically placed in exterior wall assemblies, where nailing on applied details or trim. Wood "plugging" was also used for nailing points. If you're talking "wythes", that's not the case with structural terra cotta. At least not in my experience. The standard thicknesses for exterior wall (dense) tile was 6", 8" or 12". 12" was the most common for 3 or 4 storeys. Over 4 storeys, I've always seen a steel structural skeleton, with the blocks used to fill in between. The dense, structural blocks have tremendous strength and are incredibly light-weight as compared to any other masonry building material. The exterior wall blocks typically have shell walls 1" thick and the webs are 3/4" thick. The chart below shows some testing results, but this wasn't on strictly dense, load bearing blocks. Click to Enlarge 81.2 KB