Stavspån. Hur utformningen av bleket påverkar vattenavrinningen

Abstract

Cleft shingles are a traditional wooden roofing covering method. Manufacturing is a time-consuming process and costly if it is made with high quality and it is therefore good if the life span of the roofing is as long as possible. Material selection, manufacturing method, laying, foundation and maintenance are described as determining factors for the lifespan of the cleft shingles. These factors are described in more detail in literature, but a factor that could be of crucial importance for life expectancy is the design of “bleket”. “Bleket” is the visible part of the cleft shingles when the roof covering is finished (Wedman 1998, p. 93). The shapes are described primarily as a decorative and less as a functional for water runoff. The design of “bleket” may have an impact on the efficiency of water runoff and thus the life span of the cleft shingles. The research aims at investigating how the shape of “bleket” on the cleft shingles affects the efficiency of water runoff. The goal is to see if the design of “bleket” can be another factor to be considered in the manufacturing of cleft shingles to achieve a roof covering with as long lifespan as possible. Experimental surfaces with a certain pitch and area were covered with cleft shingles and then were exposed to a water flow and the time at which a certain amount of water took to pass the cleft shingle-covered-surfaces were measured and summary for the various shapes of bleket was made. A shorter time meant a more efficient water runoff. The research is showing measurable differences in the efficiency of water runoff among the various shapes of “bleket” on the cleft shingles. Straight shingles which were chamfered were found to have the most effective water runoff. The second most efficient water run off had the shingles with a pointy end.