Historic Building Restoration, informative posts, Reclaimed Slates
Second Hand Slates | Sorting and Grading Reclaimed Roof Slates
Jul
Second hand slates
Best Practice When Using Reclaimed Roofing Slates
Reclaimed slates can produce superb roofing results, but only when they are sorted, graded and set out properly before installation. Whether you are using Westmorland, Burlington, Welsh, Spanish or stone slates, preparation is what turns salvage into a reliable roof covering.
Why Sorting and Grading Matter
Second hand slates rarely arrive ready to fix straight to a roof. Even when the slates appear consistent at first glance, reclaimed material will often vary slightly in thickness, width, length and weathered condition. That variation is part of the appeal, but it also means the slates need to be organised with care before work starts.
Proper sorting and grading make installation more efficient, help roof lines run cleanly and reduce the risk of awkward gaps, excessive cutting or inconsistent side laps. In practical terms, this process allows the roofer to use the material intelligently rather than fighting with it once the roof is underway.
In short: reclaimed slate roofing starts on the ground, not on the roof. Good preparation saves time, reduces waste and improves the finished appearance.
Two Main Approaches to Slate Sorting
How reclaimed slates are sorted depends largely on the type of roof they are intended for. Broadly, the process falls into two categories:
- Slates laid in diminishing courses – usually random sized material, laid largest at the eaves and reducing in size towards the ridge.
- Tally slates – slates of a uniform size, laid at equal gauges across the roof slope.
Both methods require grading, but the type of grading differs. Diminishing-course work focuses heavily on width, length and course planning. Tally slating, by contrast, places much greater emphasis on thickness grading and visual consistency.
Diminishing-course slates need careful sorting by length, width and usable coverage before installation begins.
Second Hand Slates for Diminishing Courses
Reclaimed slates laid in diminishing courses tend to be more random in format and are commonly associated with higher-status traditional roofs. The main types usually found in this category include:
- Westmorland slates
- Burlington slates
- Stone slates
- Welsh tonner slates
These materials are usually graded into courses rather than treated as interchangeable pieces. That means you need to understand not only slate length, but also how much width is available for each individual course across the full roof slope.
Westmorland and Burlington slates are commonly sorted into courses before fixing, with the largest pieces set low on the roof.
Reclaimed Westmorland Slates
Reclaimed Westmorland slates are random in both length and width, so they should ideally be separated by course at the point of strip if they are being salvaged from an existing roof. Doing that preserves the original logic of the roof and makes reinstatement far easier later on.
When preparing to relay them, the longest slates are placed towards the eaves. From there, the slate lengths diminish gradually as the roof rises towards the ridge. However, length alone is not enough. You also need to know that each course contains enough total width to run the full distance of the roof while maintaining proper side laps.
As a result, careful counting and course planning are essential. It is always wise to sort more slates than you think you need for each course so that the correct side laps can be maintained without compromise.
Reclaimed Burlington Slates
Burlington slates are usually handled in much the same way as Westmorland slates. They often come in larger sizes, and in many cases they are a little easier to source in useful quantities. Even so, the same rules apply: course them first, understand the available width for each course and do not begin laying until the roof has been properly planned on the ground.
Reclaimed Stone Slates
Stone slates also demand a traditional approach to sorting and coursing. Because they are natural stone and often highly variable, the process of selection, course setting and grading becomes even more important. Good stone slate roofing is heavily dependent on preparation and layout, not just on the material itself.
Welsh Tonner Slates
Welsh tonner slates take their name from the way they are typically traded: by weight rather than by piece. Like other diminishing-course slates, they are random in both length and width and must be sorted carefully before use.
These slates are often dark and heathered in appearance and have historically been associated with Penrhyn slate sources. Once graded and set out properly, they can create exceptionally strong traditional roofs with real architectural authority.
The key point is the same: random slate cannot be treated casually. If you want a good result, every course needs to be understood before fixing begins.
Random Welsh and stone slate roofs rely on disciplined sorting and accurate course planning.
Need help sourcing diminishing-course slates?
We carry changing stocks of reclaimed Welsh, Burlington, Westmorland and stone slates, and our team can help you work through likely quantities, matching and availability before your project starts.
Tally slates may be uniform in size, but they still need grading by thickness for the best finished roof.
Tally Slates | Uniform Size, Careful Grading
Tally slating is different. In this method, each slate is a uniform length and width, and all courses are set out at equal gauges. Reclaimed Welsh slates are the classic example, although Spanish and other imported slates are also commonly used in tally work.
Even though the format is more regular, tally slates still need grading. The main issue here is thickness. If thick and thin slates are mixed randomly, the roof can appear uneven and awkward, especially when viewed along the coursing lines.
Best practice is to sort the thickest slates for use towards the eaves, then move gradually into medium and thinner slates as you work up towards the ridge. This creates a cleaner, more balanced roof slope and helps the finished work look properly controlled rather than patchy.
Typical Best Practice for Tally Slates
Sort by size first
Make sure the slate batch is genuinely consistent in length and width before treating it as tally material.
Grade by thickness
Use thicker slates lower down and thinner slates higher up to achieve a more even finished appearance.
Plan before fixing
Even with uniform slates, early sorting and set-out reduce delays and improve the visual quality of the roof.
Planning and Availability of Reclaimed Roof Slates
When using reclaimed slates, planning ahead is essential. Sound second hand slates are available, but they are not limitless. Specific sizes, quantities and types can be difficult to source at short notice, particularly for full reroofing projects or specialist repairs.
That is why sourcing in advance is always recommended. If a project depends on a certain size or slate type, secure the material before the roofing programme begins rather than hoping that additional stock will appear later.
At The Reclaimed Company, we regularly hold stocks of:
- Reclaimed Welsh slates
- Burlington slates
- Westmorland slates
- Stone slates
Stock levels do fluctuate, however, so it is always best to ask early if your project requires something specific.
Choosing the Right Slate for the Right Roof
Reclaimed roofing slates are not just a material choice. They are part of a broader approach to building conservation, visual continuity and material reuse. On many projects, the decision to use reclaimed slate is driven by one or more of the following:
- Conservation requirements where original appearance must be maintained
- Aesthetic reasons where weathered roofing looks more appropriate than new material
- Environmental benefits through reuse of serviceable materials
- Matching work on extensions or repairs where new slates would stand out
When used correctly, reclaimed slates help roofs retain their character while keeping valuable materials in circulation.
