If you are building a kit summerhouse and it is supplied with felt you can simply buy rubber and use that instead.
If the supplier is also erecting it ask if they will use rubber that you supply instead of the felt they will supply. Would you be willing to pay a few quid extra for them to do it?
You may also have to sign a waiver to absolve them from any responsibility if the roof leaks at some future date.
we are buying it, we did ask about a rubber roof and and she just said no its felt and we left it there suppose we could ask, we know a roofer who could do it for us if it was straight forward just go over the top i would like him to start dismantling anything.. thanks
I fitted my roof felt from side to side with a 4" overlap and a bead of sealant in between the layers.
It stood up to a tremendous thunderstorm a few weeks ago when we experienced flash flooding on the roads.