Porch awnings differ to full awnings as they only attach to your caravan along the top horizontal section of your caravans awning rail.
Air Awnings have become very popular in recent years for there ease of pitching. The vast majority of these are Porch awnings and dispute the name these are available in up to an 8m length.
When measuring your caravan for a porch awning you measure the horizontal section of awning rail, before it curves around the front and back corner of the caravan. This will give you the Max. Length of Porch awning that will fit your caravan. Porch awnings only fit down the sides of the caravan using foam pads and rear pad poles that attach to the awning and help push the rear pad poles against the caravan. Some manufacturers also use a suction cup system or straps to help secure the sides of the awning against the caravan.
It is also worth looking at the position of the windows and doors on your caravan to give the optimal size of awning. Imagine the position of the awning on the horizontal rail and look at a size of porch awning that will cover the door and not obstruct windows. Sometimes due to the caravan design it is not possible to avoid the awning coming down the middle of a window but it is worth a little homework on the sizes of Porch awning available.