What you THOUGHT you knew about real Slate

Wednesday, November 9, 2011
Architecting Insights

Originally posted as an internal e-mail to the USA Design Staff by Armand Christoper, AIA, Principal and Director of Technical Services

Allow me to describe to all of you what is currently occurring on several of our projects, regarding slate roofing, as food for thought on your next project if it has a place for slate.  When Shyam had to specify slate roofing on the Schaefer Auditorium @ Kutztown University he contacted the Evergreen Slate Co. in Granville New York.  They own and operate a huge slate quarry that straddles the New York /Vermont border and several smaller satellite quarries in the area.  The Sales Rep. gave us a Lunch & Learn on slate which piqued my interest, even though we have never used much of it in this office due to the high cost associated with it.

Last month, I went to the Slate Company and visited the Quarry for a Continuing Education program.  While I was there I learned a lot and found a way to take advantage of the huge stockpile of material on-site that can be bought for a fraction of the cost of what would have to be specifically quarried to fill a custom order.

Slate is normally specified by color and size and shape, so an Architect/Designer can get the full range of available products from Evergreen Slate Co.  However, the cost of going into a particular section of the quarry, removing the color and quantity required is grossly exaggerated by the need to remove tons and tons of overburden (worthless material) to get to the desired material.  Once into the desired material, the quarry doesn't

just take what it needs to fill the current order.  They have to remove much more material to make the effort worthwhile.  This additional material is cut and hand split into standard thickness, standard weight and varying widths and then stockpiled in the yard.  When I saw what thirty or forty years of this practice has accumulated in the roughly 25 acre yard, the light came on for me.  If we specified what was already on-hand, and get it reserved for the job we were about to bid, we could buy it for a fraction of the price of an otherwise custom order placed later by the Contractor.

The quarry agreed that huge savings could be realized for material that was already on hand, and it was happy to work with USA this way.  The test case would be the Additions and Renovations of the William Penn School for the Allentown School District.  Jim Petro, AIA had already done a cost comparison between real slate (through normal procurement) and synthetic slate, and decided to go with the synthetic because it was MUCH less expensive and necessary to stay within budget.  I found a mountain of slate in Evergreen’s yard that was in the grey green color blend in thickness, length and random width to match what was originally on the building.  Evergreen took our drawings, did a take-off and submitted a quote.  When we compared this quote for real slate, that will last 80 years (compared to 40 for the synthetic) we were amazed to be getting it for 1/2 the price of the synthetic slate.


Andrew is already trying the same approach on the Warinanco Park Project which has historical significance and will greatly benefit from real rather than synthetic material.