Grading Roof Slates

Second hand slates will usually need to be sorted and graded prior to being installed on a roof.

Grading roof slates.

When choosing the right slate for your roof the higher the selection the more uniform the finished roof and the fewer imperfections. For further information on cupa s classification please read our guide to the grading of natural slate roof tiles. Impervious to hail and even bullets these ultra premium slates weigh 2500 to 3000 lbs per square. The astm standards for slate are some what regulated by members of the national slate association nsa with.

The best slaters will carefully grade every slate before it goes on the roof. Foliation may not correspond to the original sedimentary layering but instead is in planes perpendicular to the direction of metamorphic compression. There is a recent trend to load crates directly on to the scaffold and lay the slates straight out of the pallet without grading. Interestingly roof slates especially when reclaimed will have slight variations in terms of dimension and thickness which will need to be.

The american society for testing and materials astm is a free acting society with the goal of keeping a high national standard for materials. Read on for an understanding of cupa s natural slate tile selections and a guide to the natural slate grading on site. Slates should always be diligently sorted into three or four groups of equal thickness. The process of sorting and grading used roofing slates ensures that they can be installed effectively.

If the slate has been sorted and the roof marked out properly then laying the slate is straight forward. With its enhanced grain it is an unmistakable slate roof with an expected usage of over 150 years. Astm roofing slate grading explained. It is extremely unlikely to.

This shouldn t be confused with the need for slate grading on site. Slate is a fine grained foliated homogeneous metamorphic rock derived from an original shale type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism it is the finest grained foliated metamorphic rock. Check roof pitch and make sure that the correct size slate and lap are used. Grading roof slates flatter roofs.

However the recent trend is to forklift a pallet on to the scaffold and lay the slates straight out of the pallet without grading. Standard grade rough texture. It has the surface appearance of heavy grade in a. How does astm requirments apply to roofing slate.

This slate is split at thicknesses between 1 4 to 3 8. If the slate s have been graded and the roof has been battened out correctly to the required headlap then laying the slate is relatively straight forward. Slates come in all shapes and sizes.