I am a resident in a block of flats. During the recent heavy falls of snow the top floor flat suffered from water leaking through the ceiling. The source of the water was from melting snow in the gulley between two piched roofs (see photo) . As the snow melted the water could not escape because the gulley was filled with snow. As the water level rose it passed through the ventilation gap between the lead flashing and the slates and flowed over the edge of the lead flashing and onto and through the ceiling of the flat below. The comment from the roofing company who came to inspect the roof was that it was due to adverse weather conditions, but they were unable or unwilling to offer a solution.
Can anyone suggest a solution that will keep the water out, but allow the roof to be ventilated. The flats are 10 years old. I should say that heavy rain is not a problem.