Box gutters or built in gutters, are most commonly found on commercial buildings like schools, apartments and other business buildings, as well as older and historic homes. These gutters are actually part of the roof instead of being attached to the roof. The majority of box gutters are made of wood and extend past the wall.
Box gutters are normally lined with metal. Some though do not have anything lining it so they tend to have more issues quicker because of the wood becoming damaged and rotting. Box gutters can be more of a pain to deal with when they become damaged, leak, and need cleaning since a lot of the box gutters for most buildings are higher up. Sometimes they are more than 3 stories up so they tend to get neglected in a regular maintenance check. Built in gutters along with aluminum gutters have to be kept clean of debris and make sure they are in good working condition. If you begins to notice any over flow or leaking, they need to be attended to pretty quick.
The membrane also protects your gutters and helps with a smooth lining to help water flow continue and any possible debris flow as well. Just like how water on Duro Last roofs run off quickly due to water proof material being slick compared to other roofing materials where the water can absorb. A 2 piece compression used to help force water to drip off the 2 piece compressions instead of over the front of gutters or back onto the building.
Because these gutters are high up and pretty much unseen a majority of the time, they can be neglected from maintenance cleaning and repairs. But due to them being built-in and your roofs draining system, they are an extremely important part of your roof system and must be cleaned and maintained.