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 and was surprised by the fact that it had a graduated roof, the slates becoming shorter as the roof progressed upwards. After closer examination I found that the slate had tapered sides, which I first put down to inaccurate squaring by the trimmers. The barn was 150 years old, and typically such structures received the most utilitarian treatment. Why would anyone take such trouble, I wondered? Finally, the explanation became clear: the barn was the second use of the slate. It had originally been cut for a graduated roof on a turret! The first course of slate measured 24” x 26”, the last course 15” x 6”. Successive courses showed a more pronounced taper and the smaller slate were shouldered (the top corners clipped to allow better seating on a curved surface). This was the most unusual example I’ve seen of reclaim slate, but shows that then, as now, materials of value do well to be re-purposed.
The main reason for using reclaim is that it gives a better match to the roof being repaired. It does so in several ways: 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 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.
The thickness of slate is of concern to a slater. In the past, slate was generally split more thinly than nowadays, since the installation was a different process. Slates were laid on battens (sleepers, or split sheathing), set at intervals matching the slate 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 and at the quarry more slate made from each block. From about 1900 onwards, sheathing was more likely to be continuous, and jacks and walk-boards were used to scaffold the roof as the slate were installed. It was preferable, therefore, that the slate were thicker and could withstand foot traffic.
So a new slate in an old roof presents a problem. It is generally thicker than the existing slate. When installed it forces the surrounding slate upwards. A misstep by the roofer or time alone will cause these surrounding slates to break. A reclaimed slate of matching thickness, however, solves the problem.
Given that the use of reclaim as a repair slate 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 could be Virginia or Peach Bottom slate, the most durable of the domestic slates. 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 in 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 patina of history, industry and commerce. The value of both these roofs is that they will endure another one hundred years.
Quarries may object to the use of reclaim, since it undermines the sale of new slate. However, given that reclaim is used primarily for repair work, it might also be argued, why use a hundred-year slate in a roof that has only twenty years of life remaining? Some quarries have taken the initiative and deal in both new and reclaim.
There are other challenges in the reclaim process: judging the quality of slate can be difficult.
One time I discovered a treasure trove of Peach Bottom slate, in Chanceford, Pennsylvania. 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, the ring had gone. A tap with a hammer produced a dull thud! Stored in a basement for twenty years, this slate had dried out completely, but at the first opportunity soaked up water like a sponge.
In the past people gave away “old” slate. Nowadays 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!), carrying slate down a ladder, sorting, palletizing, hauling and counting.
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. It contributes extra value and should be compensated. Likewise, using good reclaim for re-roofing is worthwhile. It is the “look” of a slate roof that attracts most customers. Reclaim has an instant one hundred year “look” that is very pleasing to the eye. What it takes is a lot of hard work and a measure of good luck, like most business.