Our cast-iron guttering is, apparently, too shallow on the facia side. So...during heavy downpours, rainwater fills the gutters to capacity (we have a large steeply pitched hipped roof with guttering all round). It then overflows down the facia causing the wood to rot. We don't want to replace the guttering or the facia boards with plastic (hate plastic!). We have heard of a product which consists of strips of PVC sheeting (yes...I know it's plastic!) in lengths of about a metre and about 30cms wide. Each strip, about 10cms in from the long edge, is angled at about 20 degrees. This sheeting is slipped under the felt (and tiles of course) all round the roof with the angled edge exposed and dipping downwards into the guttering providing a barrier to backflow. I hope this is a clear enough description.
Would you recommend using this product to solve our problem? Or would doing the same with roof felting do just as well?
Any suggestions would be greatly appreciated.