Very well respected local 30 year family firm NFRC Craft Roofer, Master Roofer & member of building regs. competent roofer sign off scheme has quoted for new roof using Chinese slates or using 50% existing slates and rest from reclamation - property is 1935 semi with Welsh slate. I firmly questioned proposal for Chinese slate and roofer has given assurance that the product they use is superior to good quality Spanish slate and will have better lifespan than reusing existing Welsh. As mentioned, this company is very well respected and I really could not imagine them risking their reputation by giving dodgy advice. However, everything I read re. Chinese slate makes me very nervous. I want a roof that will outlive me so I'm keen to know what others think re. existing Welsh vs Chinese that comes well recommended - and with 75 year quarry guarantee and 10 year builders guarantee.
Is sounds like you have found a really good firm to do the work, so as experts their opinion should carry some weight. Please make sure that the warranties that you are given are insurance backed, as anything else is not worth the paper they are written on.
As you probably are aware, there is considerable variation in quality between quarries even in a relatively small geographical area, so I am sure that there is some excellent quality Chinese Slate, although I couldn't tell you which ones are!
Often in these situations a second opinion in the from of some more quotes can really help. You can get a recommended local roofer here:
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