As the last blog post suggested, our Market House design is based on historic precedent, and the material choices have been determined by what was available in Williamsburg during the 18th century. The foundation will be made of brick, the lower framing of white oak, and the upper framing will be poplar and pine. Shingles are to be cut from cedar, siding from cypress, and trim work from pine. All of these were common and widely used materials in the Williamsburg region during the 18th century.
It sounds simple so far. However, as many of you know, a brick or a post at Colonial Williamsburg is not as simple as it sounds. We start, as they did in the 18th century from the beginning: a brick begins as raw clay and a post as a tree. Our craftsmen then turn those raw materials into the needed form. So with the designs developed for the new Market House, we do a lot of working backwards to get the materials we need.
For the masonry, we know that it takes roughly 18 bricks to make a cubic foot of wall, which means that the Market House foundation will require 5,500 bricks. To make 5,500 bricks we need roughly 32 tons of raw clay. Approximately 25 gallons of mortar are required to lay 100 bricks, so we will need 1,375 gallons of mortar. To make the mortar we do analysis of 18th century mixes and come up with a mixture of roughly a one part lime to one part sand with minor amounts of clay and brick dust. The lime source in the 18th century was oyster shell, which was burnt to make a material called quick lime. For our needs, we had to burn over 687 gallons of shell to produce the quick lime needed for the mortar.
Our carpenters have been hard at work too, forming trees into the necessary elements for construction. To make a 10 inch by 10 inch post, we need to find a log measuring at least 16 inches in diameter and the proper length. This allows us to remove the sap wood so the framing is structurally sound. The shingles to cover the roof and protect the structure also have to be made. It takes approximately 650 shingles to cover 100 square feet of roof. To make these shingles it takes a log 18 inches in diameter and 20 feet long that is free of checks and knots. It will take 9,360 shingles to cover the roof, which means (you guessed it) 9,360 nails from our blacksmiths. …..
And so it goes. The process is carried out over and over to assure that the building is constructed as accurately as possible. The finished product will combine material knowledge and trade skills of our 18th century predecessors carried out by our present day historic trades workers.
Contributed by Matt Webster, Director of Architectural Preservation