Finishing the Outside Walls
Exterior Render Coat
The exterior of the finished stone walls needed to be protected from the elements. Unprotected, rain would erode the sand stone and wash away the clay mortar.
A rendering coat consisting of clay, manure and short pieces of straw were placed in a shallow pit and mixed by walking a horse through the mixture.
Getting the right mix of ingredients was part of the craft of stone-slab building. Small lengths of straw in the mix provided a rough texture to the exterior and diverted water as it flowed along the surface. The mixture had to be wet enough to stick to the surface and spread evenly when applied.
The mixture was applied to the surface by a technique known as harling. As the name implies, a handful of the material was thrown at the wall. This technique ensured that the finished surface had as much texture as possible and allowed moisture to escape.
The purpose of this exterior coat was to protect the interior wall. It was expected to erode away over time, requiring a new coat from time to time.
At one point, the Hutmachers experimented with using Portland cement as an exterior render coating to reduce the amount of maintenance on the house.
The cement kept the exterior finish from washing away but kept moisture inside the walls, causing the sandstone to deteriorate and weaken. As a result, the north wall of the original house had to be replaced because the cement exterior finish caused the wall to weaken and bow out.
Finishing the Outside Walls
