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National Slate Association (NSA)

Early in 2014, the NSA met in Florida to discuss and define who we are and what we stand for. The last time this happened was in 2002, in Saratoga, New York. Before that, in Bomoseen, Vermont, 1922.

Like all the best ideas, the answer was ultimately very simple: to promote slate in North America, and to promote the highest standards of materials and installation.

This Purpose Statement was achieved after much discussion, a dialectic that reflected a deep respect for the tradition and history of slate, while looking to ignite a new fervor for a national heritage that has value and relevance to the future.

The National Slate Association is the place where Quarriers, Suppliers, Consultants and Slaters meet. Technical information is shared, and business connections are made. Camaraderie is found as we celebrate our achievements, but most important of all it is our opportunity to give back to the industry. It is our efforts in this industry that have enabled us to make livings and raise families. Now is our chance to tend to the industry; to ensure it is vibrant and strong for our successors to enjoy; to ensure that standards are kept and raised, that the trade we love is held high and respected in North America.

Visit our website.

Why Join National Slate Association?

The National Slate Association appreciates the history, beauty, and proven nature of natural slate while dedicating it to the mission of supporting it as a material. Other materials feel wasteful and inferior compared to the longevity and eco-friendly nature of slate. The National Slate Association has come together to promote and educate how to use natural slate as a roofing material. By joining, you’re engaging in a community of like-minded people who respect the centuries-long tradition of slate installation. Learn installation specifics from the brightest minds the industry has to offer or shake hands with suppliers who will keep you competitive in the trade. Be listed in the NSA Member Directory as a qualified business in the industry. These are all benefits of joining this prestigious association.

Join the NSA!

Slate Colors & Characteristics 

Natural slate is a microcrystalline, fine grained metamorphic rock formed 400 million to 550 million years ago, with its beginnings as sedimentary silt washed into ancient seas. These sediments accumulated on the sea floor for 150 million years, forming a bed of clay and shale several thousand feet thick. During later geological upheaval, these sedimentary shale beds were lifted from the ocean floor, folded, and buried on the North American continent. Sediments accumulated on the sea floor were exposed to extreme pressures which lead to the chemical and mineralogical transformations you see today. As a result, the sedimentary bedding plains of the original clay and shale are totally independent of the metamorphic grain of the resultant slate bed. Natural slate has many uses which include roofing material, floor tile, countertops, wall cladding, blackboards, and even tub and shower enclosures.

Weathering Designations

The color of a natural slate is derived from its chemical and mineral composition. Chlorite produces green slate, hematite the purples, carbon the grays and blacks, and hematite and iron oxide the reds.

Descriptions of color can vary widely from supplier to supplier, but generally, roofing slate produced in North America falls under the general color descriptions of black, gray/black, gray, green, gray/green, purple, variegated purple, mottled purple/green, and red.

One of the unique and aesthetic advantages of natural roofing slate is the subtle variation in color, shade, veining, and grain of each individual slate shingle on a roof. These color variations should be expected.

Learn more.

Who We Serve


Join a community of contractors across the USA that is supports by the National Slate Association!


Learn more about how the National Slate Association supports architects across the USA!


The National Slate Association helps homeowners across the USA maintain their homes quality!

National Slate Association’s Mobile Field Guide

mobile.slateassociation.org is available free of charge via an internet browser on your smart-phone* or tablet when an internet connection is available.

Or you may also scan the QR code here with your QR reader.

Download the Mobile Field Guide press release. 

*The NSA Mobile Field Guide is best viewed on iPhones, iPads and the newer Android phones.

*Windows® smart phones are not supported at this time.

*The mobile site is not intended or formatted for desktop computers or laptops.

View the Mobile Field Guide today!

The Roman Catholic Church of the Archdiocese of New Orleans, Notre Dame Seminary

Complete roof restoration of Roman Catholic Church of the Archdiocese of New Orleans, Notre Dame Seminary, including 840 sq. slate roof restoration/replacement; custom copper gutters & hangers – 3,000 linear feet; custom copper hip & ridge to match originals – 2,000 linear feet; gypsum deck repairs – 10,000 sq. ft.; new standing seam copper dormer tops to match originals – 26 units; new copper flashings; new custom copper finials to match originals; new 16′ tall copper cupola to match originals; carpentry/paint-work on dormers; clay tile roof repair; and built up roofing systems on flat roofs.

Learn more.

San Francisco Theological Seminary

San Francisco Theological Seminary of Northern California was originally constructed in 1891.

Repairs to the slate roof were required.

View the full project!

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National Slate Association: New Lives in the Valley (1850-1920)

Gwilym Roberts led a very successful academic life as Dean of Arts and Humanities at the University of Farmington, Maine. Both his father and two Welsh immigrant grandfathers were slate workers from Brownville, Maine, and this heritage became the subject of his book, New Lives in the Valley. The Valley ...
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National Slate Association: Buying and Maintaining a Home with a Slate Roof

David Robinson has been in the residential slate business for more than twenty years. He understands the pitfalls and benefits of buying a home with a slate roof. In this book he provides a wealth of information, clearly explained, to assist homeowners. Jack-leg contractors are exposed, the beauty and longevity ...
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National Slate Association: Slate Roofs Design and Installation Manual

This Gold Circle Award-winning book masterfully renders every design and installation detail to be found in slate roofing. Architectural drawings accurately illustrate flashing and roof lay-out. Alternate solutions to slate roofing problems are provided. Architects, Consultants, Slate installers and Designers rave about this book! Purchase here!
Read More

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