June 2024 Monthly Meeting

Typical industry standard recommendation for slate replacement is at a 20% or more failure threshold. There are no field or lab tests that currently predict the remaining lifespan of existing weathered slate. However, ASTM C406 Standard Specification for Roofing Slate establishes the “grade” of new roofing slate, associated with projected life expectancy. Peter Meijer Architect PC sent slate samples to several labs to conduct C120 Standard Test Methods of Flexure Testing of Slate, C121 Standard Test Method for Water Absorption of Slate, and C217 Standard Test Method for Weather Resistance of Slate. These test results gave a gauge to the existing slate’s performance. A critical aspect of determining the life expectancy of archaic/older material is understanding the limitations associated with modern ASTM test methods. ASTM standards are not always accurate predictors of slate quality but are good sources of empirical data. Peter Meijer Architect PC used our experience and broadened our research into longevity by including testing means and methods from Europe and other countries with a longer history of slate testing. The standards in use on the market to certify slate are the British Standard Institute, BS EN 12326-1:2014, Slate and Stone for Discontinuous Roofing and External Cladding, and the United States ASTM C406.

Peter Meijer. principal, has over 30 years of professional experience with an emphasis on the preservation and assessment of older, existing, and historic buildings. As a professional architect with a background in scientific research, He has developed his career with a focus on the unique building sciences associated with existing and historic resources. He has become a well-regarded expert on the diverse issues affecting older buildings both regionally and nationally.

Hali Knight has 10 years of professional experience, primarily with a focus on restoration and building enclosure design for existing and historic structures. While at Peter Meijer Architect PC (PMA), she has led many projects that include assessments and repair recommendations for historic materials such as masonry, slate, and terra cotta. Many of PMA's projects use material testing and on-site evaluation as tools to direct building enclosure repair methodologies and priorities. In addition to restoration work, she has worked on several large-scale renovation projects that include seismic upgrades and tenant improvements.