can you elaborate on how the detergent is causing a dam or allowing the water to move laterally?

Apparently when I sprinkled it on it tended to clump along the ridge (on top of the ridge vent). I figured it was most efficient to allow rain water to gradually wash it away down the roof over time - like a time release sort of thing. However the ridge shingles are the weakest link of the roof in that they are flat on top. Water tends to run a little underneath the overlap of the next shingle before beginning to travel downslope. If the granuales of detergent do not dissolve, they tend to solidify and create a dam beneath this overlap - thus blocking the water from turning downslope. It now has nowhere else to go but further lateral to the nailhead of the shingle and then down beneath from there. I also have some limited daming beneath shingles even on the main 3:12 pitch roof!

Apparently when I sprinkled it on it tended to clump along the ridge (on top of the ridge vent). I figured it was most efficient to allow rain water to gradually wash it away down the roof over time - like a time release sort of thing. However the ridge shingles are the weakest link of the roof in that they are flat on top. Water tends to run a little underneath the overlap of the next shingle before beginning to travel downslope. If the granuales of detergent do not dissolve, they tend to solidify and create a dam beneath this overlap - thus blocking the water from turning downslope. It now has nowhere else to go but further lateral to the nailhead of the shingle and then down beneath from there. I also have some limited daming beneath shingles even on the main 3:12 pitch roof!

Hello. Although we see shingles installed on low slope roofs on a regular basis, in my opinion a 3:12 pitch is not recommended for this type of installation. That being said, the roof was just redone and with a couple of adjustments you should be OK. If you are having ice daming problems at the eave, you can contact a responsible roofer and ask them to install a steel starter strip along the eave of your roof with a width of approximately 24 - 36 inches. Imagine the last few rows of shingles being replaced with flat, color-coordinated steel. The metal will absorb the sun's energy and warm enough (even in very cold temperatures) to melt snow & ice which will then shed itself from the roof. Thus eliminating any ice buildup.

As far as the detergent issue goes, I would need either more details or a photo as I can't quite understand how it has caused daming. If you have a digital picture, please feel free to send it and I will try to assist you.

David Mackey, Vice President

MACWEST Steel Inc.