If it is capped tight, it is no longer in use and that keeps rain and birds out of the pipe. If it has a cap that is above the pipe like an umbrella, it is for the same reason and to let fumes or exhaust out.
A pipe extended above the roof level is a soil pipe.
Rain has the potential to splash about 8 inches vertically. Check with the local fire code for the required height above a roof for a stove pipe. Typically fire codes will require the opening of the stove pipe to be at least 2 feet above the highest adjoining roof area.
Lead flashing.
TERRA COTTA ROOF
It has a retractable roof.
shack
If your policy has coverage for accidental water discharge, the resulting damage would be covered but only after the owner has repaired the damaged pipe. If your pipe busted as the result of a covered peril such as fire, wind hail etc (see your schedule of covered perils) then the pipe itself would also be covered.
like a boss
first you have to calculate the circumfrance of the 4 inch dryer pipe. Then once you have calculated that you must do the answer times by the hole in which is designated in the roof. This answer will then tell you how easily it will actually be to fit the dryer pipe through the roof. if the answer is higher then 10 you must make the hole in the roof larger. Then reed it through and lock it in place. Then you can dry as many things as you like.
Generally there is no need for a roof jack in a porch roof. If the porch ceiling will be covered you could run a vent through the roof.
It is called a gutter.
B-vent pipe.