ASHRAE Journal - June 2009 - 82

Photo 2 (above): Exposed timber frame. One hundred and fifty year old timber frame house being renovated. Exterior horizontal sheathing boards and weatherboards removed. Note the close spacing of the vertical intermediate posts. Photo 3 (above right): Wattle-and-daub. This is a timber frame house in Wales, United Kingdom, with the wattle-and-daub exposed. Note the weaving of the wattle. Photo 4 (right): Waltrop House. Germany, 1400, wattle-anddaub infill panels with an exposed timber frame. Wattle-and-daub has a lime plaster coating. Timbers are coated with tar. spaced more closely together between the larger bigger posts (Photo 2). It also lead to the introduction of layers of horizontally installed boards—thicker than the clapboards (called sheathing) all for the purpose of supporting the clapboards. So, we had two approaches going here. Which one was selected often depended on the presence of a sawmill and the water to power it (thicker boards tended to be sawn); whereas the clapboards were split and didn’t need a sawmill. Without a sawmill we tended to see more vertical smaller posts spaced more closely together in place of sheathing. We still see this distinction today regionally in the United States and in Australia and New Zealand: no sheathing, just an exterior cladding. Stucco in California is typically installed on open studs supported only by building paper, piano wire and metal lath. While all of this weatherboard, clapboard and sheathing evolution was going on, developments were also occurring with the other stuff used as infill between the posts and staves. This other filling was often re# ferred to as “noggin,” and typically took the form of wattle-and-daub. Split branches or slats were woven together between vertical stakes creating a lattice (wattle) that was traditionally covered with a plaster-like material made of some combination of dirt, clay, sand, animal hair and animal dung and straw (daub) (Photo 3). This technology predates the Greeks and Egyptians. Daubers were the folks who plastered the outside of wood-framed buildings.# The ingredients yield the classic combination of binders, aggregates and reinforcement. Combinations that today form the basis of modern stucco. Wattle-and-daub panels that infilled exposed timber frames gave us the classic Tudor look of lime plaster (white) coatings between tarcoated (black) timbers (Photo 4). The problem with wattle-and-daub was its water sensitivity. It tended to crack and needed to be coated with whitewash and lime plaster to keep the water out. Over time the wattle evolved into horizontal wooden lath supported on smaller vertical members called studs. Leaving the timber frame exposed was eventually found to be a bad idea. When the timber frame moved, it further cracked the infill wattle-and-daub panels, leading to more water entry. As wood frame building technology evolved, the timber frames tended to get completely covered with lath-and-daub, thereby protecting the timber frame. This complete plastering of the exterior to improve weather resistance became known as pargeting Today we call it stucco, and it is made from Portland cement, sand and water. Sometimes lime is added to increase workability, flexibility and increase water vapor permeability. As an additive, lime turns out to be very desirable, which is a lesson that seems to have been lost in more recent times. Over time the wattle disappeared, but the stucco stayed. The wattle as a support for stucco was replaced with horizontal wooden lath and then board sheathing with building paper and a metal lath. It can be argued by that one evolutionary path for sheathing was wattle to wood lath to board sheathing to plywood to OSB to insulating foam-board sheets. All this sets the stage for three really big things that didn’t seem like really big things at the time. The place was the American Midwest and the time was the first part of the 19th century. The first really big thing was the shortage of skilled labor. The heartland around 1800 did not have many skilled carpenters or stonemasons or skilled anything. The second really big thing was the development of machine made nails. Nails used to be made by hand by smiths. It was a family cottage industry kind of thing. Really. Then a bunch of American entrepreneurial inventor types came up with machines that could make nails fast and cheap. The price of nails fell so fast that by the 1850s nails cost less in Chicago than the tax on European nails. The third really big thing was the milling of logs into dimensional pieces of lumber—each one the same as the next—and the really important part is that these dimensional pieces of lumber were mass-produced. These three big things lead to one of the greatest construction booms in history and the advent of affordable housing. The nails allowed us to get rid Frank Nunes, when I refer to you as a “dauber” I am not insulting you. It was an honorable old profession, and you are certainly getting older. ** Pargeting is often referred to as the decorative relief in the plaster itself. Many plasters were applied with elaborate decorative patterns. Use of the term varies with geography and age. I was taught that a “parge” coat was the cementitious rendering applied to the exterior of masonry foundation walls (to reduce groundwater) or to the interior of masonry mass walls (to reduce air leakage and water penetration), and finally to the interior of chimneys to improve gas tightness. 82 ASHRAE Journal ashrae.org June 2009

ASHRAE Journal - June 2009

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