GUTTER SIZES
Plastic gutters come in three common sizes (measured as the width from lip to lip):
• 75mm (3in) – for extensions and outbuildings
• 100mm (4in) – for most house roofs
• 150mm (6in) – for house roofs of very large surface area The 150mm size carries roughly seven times the volume of water that the 76mm size can take, and three times as much as the 100mm size.
A CAST IRON ALTERNATIVE
It is still possible to buy a new cast iron guttering in several ‘classic’ profiles as a match for existing gutters, but it’s expensive and very awkward to install.