Having had National stables recommended to me imagine my disappointment when my roof started to leak in 3 different places after only 10 years! Onduline is supposed to have a 15 year guarantee , but they say it was an installation error and National stables say it is down to Onduline . Nobody wants to help or admit liability. So please don’t believe all that is written on websites and brochures , this 15 year guarantee is not worth the paper it is printed on , and if you are thinking of using either National stables or Onduline my advice would be to avoid both !