Chinese Slate: is good quality?

03/02/2022

Chinese slate is a popular type of roofing slates around. Its relatively low cost makes it a popular choice for many roofers and their customers. Chinese slate has been available to UK customers for just over twenty years, and in that time, its reputation has had its highs and its lows. This is the third article in our series on roofing slates. You can read about Brazilian slate here, and local Delabole (or rag) slate here. These articles are helpful if you are trying to make decisions about which slate to use in your roofing project.

What is slate made from?

Just like Brazilian and rag slate, Chinese slate is a naturally-found material. It is made from clay, sand and volcanic dust (which makes up mudstone and shale). This mudstone, or shale, is heated and pressurised at low temperatures as more sediment, rocks, water and other natural materials cover it over.

We know slate to be mainly grey, though depending on the various minerals and chemical compounds found in the sediment, slate can look black, red, silver, green or purple. This variation in colour and form is part of what makes slate so aesthetically pleasing, as well as strong, weather-resistant and easy to work with.

Click here to read more about the fascinating geology of slate.

Why does Chinese slate have a bad reputation?

It’s a great question. Over the years, Chinese slate has been regarded as a low-grade roofing material. But why is this?

As Chinese slate started being imported into the UK, a few Chinese quarries sold ‘fading slate’ to the British market. You may have seen ‘fading slate’, as it is also common in low-grade Spanish slate. You will be able to identify fading slate by its light grey colour, and maybe tinges of brown, almost like the slate has rusted. Becuase a few quarries were selling this fading slate at ‘full price’, customers and contractors were unable to tell which slate was high quality, and which slate was low quality. Customers and contractors alike were very upset with the poor quality of this slate, and so the culprit quarries were shut down. Chinese slate is now more regulated, and every batch of slate imported is of British Slate standard.

Chinese slate is now fairly reliable, and any poor quality, fading slate that you see out-and-about will have probably been installed before this material was strictly regulated.

What are the characteristics of slate from China?

In 2020, the Chinese slate industry discovered a seam of slate that is of better quality than that from previous seams. This slate is similar in its cut and finish to Welsh slate, and so Chinese slate can offer a similar look for a little less than slate from Wales. Chinese slate, like Welsh slate, has a vivid colouring and a tactile texture. This means that as well as looking good on a roof, Chinese slate can look great on your kitchen floor too!

Why is Chinese slate cheaper than some other slates?

It’s partly to do with how Chinese slate is cut. With other slates, there is often waste rock, but Chinese slates are cut in such a way that reduces waste rock.

So are there any drawbacks?

The slate is imported from China, and because of this, some customers would prefer to use slate that has come from quarries a little nearer to home, such as Welsh slate or rag/ Delabole slate. This is sometimes a more sustainable and eco-friendly option, and supports local economies and jobs.

Do we use Chinese slate?

Bristow and Reeve don’t use Chinese slates often, if ever; we can’t always trace the health and safety regulations for the quarries to make sure that the workers are being fairly paid and treated well. Slates from Chinese quarries are still often cut to irregular thicknesses, which can make them difficult to work with, costing more time and money. This is why we don’t tend to use Chinese slates.

Do give us a call if you would like to find out anymore about our materials, suppliers and roofing practice.