Post Number: 1
|Posted on Tuesday, January 30, 2018 - 02:46 am: ||
Slate has remarkable characteristics that it radiates grandeur, imbuing any building with beauty. The builder and the owner see in the finished product, what they imagined at the outset. For that reason, they need to be educated throughout the process. While ASTM C-406 Standard Specification for Roofing Slate is a helpful guideline to the suitability of natural slate as a roofing material, it does not ensure the architect, roofing contractor or building owner a sound and aesthetically appealing roof. All parties should be aware of material or delivery shortcomings not addressed by ASTM testing. To ensure the desired roof appearance over time, specifications for slate should include the color change characteristics as; unfading, semi-weathering or weathering. These color-weathering characteristics should be clearly understood by all parties involved in the selection and supply of roofing slate. Specifications for unfading slate should require certification from the supplier that the slates shall contain no visible inclusions of oxidizable iron pyrite. Substantial inclusions of iron pyrite which oxidizes when exposed to the weather, leads to undesirable rust streaking of the roof. The specification of “ASTM S-1” or “Unfading” slates alone is not enough, as many of these offending slates are currently promoted and sold as unfading and may meet ASTM requirements as an S-1 slate.
Every natural slate roof is unique in some way. It is important for the building owner, architect, general contractor, roofing contractor and slate supplier to agree (before the slate is ordered) on all aspects of the supply and installation. The appearance of a slate roof can change dramatically with color/texture variations in the slate, and with the installation practices employed by the installer.