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.
With metal lining one big problem that can happen is the seams breaking or expanded due to the expansion and contraction of metal. This can leave room for leaks to seep into the wood and also into the interior of the home or building. Metal linings can also become rusted or corroded if not maintained with a coating that can protect from rust and corrosion. There is another option in lining them to help with a smoother draining system so they do not get clogged and do not need new metal lining as often as some materials do; this would be to use a EPDM or PVC membrane that is waterproof and the seams are hot air welded so they leave seams absolute to any leaking.
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.