Walking Our Talk

The Story of Nel-Stone

One of the more intriguing tidbits we uncovered while researching the history of 1712 Holmes was a reference on the 1926 building permit to Nel-Stone construction blocks.

The Nel-Stone Precast Monolithic System was a proprietary building material developed after World War I. It played a role in the early development of concrete- block construction technology, although known examples across the country are fairly rare.

On March 30, 1920, William E. Nelson of Fort Worth, Texas, patented a special mold that created a concrete block with coved edges. Reinforcing bars inserted into the coves stabilized the wall structure. Nelson registered a trademark for the product, which he termed Nel-Stone. The production company was initially based out of San Antonio, Texas. There was a franchise in Los Angeles and a manufacturing plant in Carthage, Missouri.

The unique design reduced construction time and costs by “eliminate[ing] form work in monolithic concrete structures of all kinds.” An adjustable mold produced blocks of various sizes to meet specific projects requirements, although the 12-by-12-4-inch blocks used at 1712 Holmes were most common. Steel was the typical reinforcing member, and cement was used as a grout between the blocks. The continuous reinforcing members gave Nel-Stone walls a distinct stacked appearance. The infilled windows at 1712 Holmes show how the Nel-Stone contrasts with the staggered coursing associated with modern concrete blocks.

Reinforced concrete was still a fairly new construction material when Nelson patented Nel-Stone. A number of companies offered similar products. The S.P. Stone Company and the Flexo Concrete Mold Company produced similar square blocks, but these had straight notches for reinforcing bars instead of the rounded notches of Nel-Stone. The textile block designed by Frank Lloyd Wright also featured grooved edges for reinforcing bars. In fact, the patent for Wright’s molding apparatus was so similar to that of Nelson’s that Nelson threatened to sue Wright for patent infringement. Apparently the men settled their differences since no lawsuit was ever filed.

Nel-Stone blocks are known to have been used for only one other local building, a parking garage at 14th and Baltimore designed by McKecknie and Trask, regional leaders in the field of reinforced concrete. That garage no longer exists, leaving 1712 Holmes as the only known example of this construction technology in Kansas City.