Reclaim slate is the name given to slate taken from an existing roof, usually during a "tear-off", that are subsequently re-used. This has been practiced by roofers since slate was used as a roofing material.
I took down a barn in Columbia, Pennsylvania, about a year ago. I was surprised by the fact that it was a graduated roof, changing lengths as the roof progressed, then after closer examination to find that the slate, especially the smaller slate, had tapered sides. The barn itself was 150 years old. The explanation finally was that this slate had been used before as a graduated roof on a turret! The first course were 24 x 26, the last course 15 x 6 (Anyone wishing to purchase 8 SQ of this pristine Peach Bottom roof may contact me).
The main purpose of using reclaim is that it gives a better match to the roof being repaired. But in which way does it "match"?
The patina is probably the most rewarding aspect of matching. Weathering green slate, for example, fade to tan, peach and salmon colors and a reclaim slate with the same patina fits perfectly into the roof's design.
All slate, unfading or not, are subject to atmospheric pollution. Sometimes an over-hanging oak tree, lichen or moss, change the original appearance of the slate. A reclaim slate, however, can be taken from a similar location and provide the perfect match. In each case the eye-jarring effect of a new slate in an old roof is avoided (see photo).
Thickness is a serious concern for a good slater. Slate from the early twentieth century and before was split very thinly in comparison to that from today's quarries. One reason being that installation was a different process. Slates were laid on battens (sleepers) set at intervals matching the exposure. Roofers never stepped foot on the slate (this is still practiced in Europe), always working to the side. Thus thinner slate could be used. Now jacks and walk-boards ascend the roof as the slate are installed. It is preferable that the slate can withstand some foot traffic (the 8 SQ of Peach Bottom I have could withstand a stampeding herd of elephants).
So a new slate in an old roof presents a problem. It is generally thicker than the existing slate. When installed it stresses the surrounding slate upwards. A misstep by the roofer or time alone will cause these surrounding slates to break.
Given that the use of reclaim has validity, what criteria needs to be applied?
For me, two good lower corners and a ring to the slate is satisfactory. Some slate, like Chapman or Penn Black, might not have a ring, but must at least be equal or better than the slate already on the roof.
Using reclaim for re-roofing requires a different calculation.An addition to an older house might look a lot better with slate that look similar to those on the original building, but for re-roofing I think the selection process has to be more stringent. It is unacceptable to install a deteriorated Penn Black slate on an addition just because it "matches" the existing roof. The longevity of the slate has to be a factor. In which case, the reclaim would likely be Virginia or Peach Bottom slate, the most durable domestic slate. There are existing roofs of Peach Bottom that are 250 years old. My own house has a Peach Bottom roof taken from a barn after 120 years of use. There was no hesitation putting this material back on another roof!
The beauty of a reclaim roof is the patina. Slate salvaged from rural areas have an untouched and unique subtlety of color. From urban areas slate takes on the history of industry and commerce. The value of both these roofs is that they will endure another one hundred years (on which subject I still have the 8 Sq of Peach Bottom that I took from a barn in Columbia, PA, that first found use as a turret. Probably in Europe!)
Quarries may object to the use of reclaim, since it prevents the sale of new slate. This may be countered with the question: why use a hundred-year slate in a roof that has only twenty years of life remaining?
There are other challenges in the reclaim process: judging the quality of slate can be tricky.
One time I discovered a treasure trove of Peach Bottom in a barn. It was 18 x 12, with a perfect face and rang like a charm. I took it back to the shop in a rain storm and showed it to my work-mates. To my great disappointment, every piece thudded like wet cardboard. Stored in a basement for twenty years, this slate had dried out completely but soaked up water like sponge the first chance it had!
In the past people gave away "old" slate. Nowadays (curse the internet), we often have to bid against others in the business. Sometimes it's just not worth it. The handling process is endless. First the removal from the roof (try a bank-barn on the lower side!), then carrying slate down a ladder, sorting, palletizing, hauling and counting.
I visited rural PA recently and was met by a very confrontational customer. He showed me three slate. One was cracked, the other had tar on it and the third was two inches shorter than the others.
"What's it worth?" he asked.
"What's what worth?" I asked back.
"The whole roof," he said. "Forty squares. I already got one offer."
"Hmm" I replied. "Take it!"
That after a three hour drive in rural Pennsylvania.
There is an exchange, but it's very messy. I find myself paying too much or too little, hoping it will come out in the wash. There is a sound use for reclaim as repair slate that contributes extra value and should be compensated. Likewise, using the best for re-roofing is worthwhile, especially poignant in our recycling era. It takes a good slate man to know the material, and integrity to deal with both his sources and customers.
On which subject, I still have 8 SQ of Graduated Peach Bottom for sale. A roof of ethereal beauty!