Our ClassicBond porch roof kits are a modern alternative to traditional roofing felt with major added benefits.This kit has been designed with the correct components to be fit to a Porchwith a flat roof.The Membrane size is the same as mentioned in kit size, you will need to ensure you have enough overhang. For a Porch roof you will need to add 300mm to the Width and 300mm to the length. For example, if your roof is 3.5m length x 5m width, you will need a 3.8m x 5.3m minimum kit size.Please Also note EPDM Is designed to be laid over Osb3/Timber Boards and should not be overlaid on to existing roof surfaces over such as Felt/Asphalt.