Herman Kwok, M.Eng. 2013
Supervisor: Dr. Fitsum Tariku
The main functionality of a shelter, essentially a house, is to keep ourselves and our assets protected. The environment outside can be very harsh at times and we want to stay warm and dry. Not surprisingly, the building assembly itself, other than the cladding and the very outer shell, is best to be kept warm and dry. Moisture problem has always been the number one issue that can affect the performance of a house. This includes the durability and integrity of the house structure.
Precipitation is the most common moisture source construction designers focus on. As much as water is coming from the top down, it can also come from the bottom up. Although foundations are sometimes constructed out of pressure-treated lumber, most of the time they are poured concrete. The foundation of a house is often under continuous contact with moisture. This is mainly due to wet soil in a wet climate zone, high water table, or a combination of both. This creates a problem. The wood frame structure sits on the foundation with the sill plate in constant contact with the damp concrete. The building code requires the sill plate to be pressure-treated if less than 8″ above the grade. The treated sill plate has resistance against rot; however, it doesn’t stop or retard moisture movement, which is the cause of rot growth and decay.
This research study examines the need of sill gaskets and their effectiveness in restricting moisture transfer. A customized wall panel is built and erected at the state-of-art building science research facility at the British Columbia Institute of Technology in Vancouver, British Columbia. Different methods used by the industry to address foundation to wooden frame are experimented in the test wall. The use of sill gaskets is one of them; however, it is only required by code as part of an air barrier system. Preliminary experimental results suggest that the use of dampproofing and sill gaskets help restrict moisture transfer. Sill gasket is most effective in limiting moisture rises and fluctuations in the sill plate. In addition to being an air barrier, sill gaskets function very well as a moisture barrier.