What Do Slate Selections Mean – And How to Choose the Right One
If you’ve ever asked yourself, “What do slate selections mean?”, you’re not alone. With so many types of slate terms flying around, from Ultra to Premium to Standard, it can be confusing to know what types of slate you’re really buying. Worse, there’s no formal industry-wide definition for these grades, so every supplier uses slightly different language.
At Independent Slate Supplies (ISS), we believe in clarity, so here’s a straightforward breakdown of what slate selections are, what you can expect when choosing a product from the ISS portfolio, how they differ, and how they should influence your choice of slate.
Types of Slate – What Are Slate Selections?
Slate selections describe the quality, consistency, and expected performance of natural roofing slate. All of the slates we supply, whether Ultra, Prime, or Commercial/Standard, are tested and meet or surpass key UK performance standards for water absorption, thermal cycling, and sulphur dioxide resistance. Only slates labelled “T2” under British Standard tests may not conform to every UK benchmark and can show a higher risk of oxidisation.
Because slate is a natural material that varies from quarry to quarry, selections help you understand what to expect in terms of sorting, handling, installation time, and final appearance. There’s no single trading standard across the market; for example, other suppliers use terms like Best, First, or Classic to convey similar ranges of quality.
Our Types of Slate Selection Categories
Ultra Slates
Premium Selection
What does this mean? The finest slate available from top quarries, with extremely consistent thickness, flatness, and colour, and minimal variability.
Why it matters: Faster sorting, lower wastage, simpler installation, and a cleaner final look.
Who it suits: Roofers who want efficiency savings and a high-end finish.
Expected wastage: ~5%
Guarantee: Typically between 50 and 100 years.
Price point: Towards the higher end.
These slates are equivalent to what some suppliers call “Best” or “Excellence” grade.
Prime Slates
Mid-Range / Classic Quality
What does this mean? An excellent all-round slate with more natural character and variability than an Ultra.
Why it matters: Requires slightly more sorting and grading but can deliver outstanding appearance and performance.
Who it suits: Experienced roofers who value a balance between cost and premium looks.
Expected wastage: ~7.5%
Guarantee: 50 years
Price point: Mid-range.
This aligns with what some suppliers might call “First Selection” or “Mixed” grade.
Commercial / Standard Slates
Cost-Effective Choice
What does this mean? A reliable slate that meets core performance standards but has more natural variation and requires more sorting.
Why it matters: Greater sorting time and potential wastage, but excellent value for projects where cost is key.
Who it suits: Roofers comfortable working with less consistent slates and prepared to invest extra time on site.
Expected wastage: ~10%
Guarantee: 30 years
Price point: Towards the lower end.
Some suppliers use names like “Classic” or “Standard Grade” to describe similar slate grades.
Brazilian Roofing Slate
Brazilian slate, commonly classified here as Commercial/Standard due to increased brittleness, remains one of our best-selling slates thanks to its long-term performance and consistent appearance once installed.
What does this mean? A consistent slate that is more brittle than slates from other countries of origin.
Why it matters: Requires some degree of sorting and grading on site but can deliver a fantastic appearance upon completion.
Who it suits: Experienced roofers who understand how to work with more brittle slates and are looking for excellent value projects with a strong final aesthetic.
Expected wastage: ~10% (hook-fixed) / ~15% (nail-fixed)
Guarantee: 30 years
Price point: Very good value for money.
Despite the low price, complaints are rare and, due to the good consistency and appearance of the stone, it requires similar sorting and grading to that of a Prime slate.
Types of Slate Guarantees
It’s worth mentioning that some importers promote extreme guarantees on basic slates to upsell their products, with no intention of honouring them. At ISS, we aim to be as honest as possible, reflecting the minimum expected lifespan of each slate. In our next publication we will cover guarantees in detail, including how you are protected and where you may be exposed.
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We hope this provides useful clarity and encourages people to think more carefully about their slate selection, rather than focusing solely on price.
If you’d like to discuss a specific project or concern, give us a call; one of our team would be happy to talk it through with you.
Don’t Judge a Slate by its Appearance!
Here are some examples of Ultra, Premium, and Standard slates, see if you can spot the difference…
