Home>Discussions>EXTERIORS>Green ice and icicles on roof
4 posts / 0 new
Last post
b_r
Green ice and icicles on roof

I’m completely baffled.

I’ve got what looks like a green ice damn above my gutters creating green icicles on my house. I’ve attached two photos: one long shot and one close up. In fact, the ice is getting greener and what looks like it started on one side of the gutter now is present all across the gutter. I also feel like there is a lot of it, probably a couple of inches thick running 40 feet or so.

I have a gabled roof and the front has clear icicles, but the back is dark, green. None of my neighbors have green icicles. The roof has two chimneys, a vent stack, several vents, and a roof vent. The only thing that has changed this year was I installed gutter guards to block the leaves this summers.

I just have no idea why the ice is green and what is causing it?

Timothy Miller
Re: Green ice and icicles on roof

Howdy appears that down spouts are a way from this corner in your photo. Consider adding another down spout close to this area so the water drains instead of pooling in the gutter. Is this the N exposure of the home- water freezing and pooling in the gutter may be issue again another down spout may resolve the isse. Are ya sure the gutter is not blocked with debris so this area is not draining?

b_r
Re: Green ice and icicles on roof

This is the south side of the house. As you noticed there is ice damming going on. The gutters are clean and do a good job in higher temperature of clearing the water; this was January when it was 10 degrees outside and that portion of the house is poorly insulated.

I handled the ice damming by using the tip on TOH where you fill a stocking full of calcium chloride (I used magnesium chloride) and tossed it up perpendicular to the gutter so that it would try to melt a channel in the dam for the water to escape. I went through a half a dozen pairs of pantyhose and a bag or more of salt, but I think I kept just ahead of it so that it didn't seep through the roof!

But, what my original question was about was the dark green color of the ice on this portion of the house. On the other side of the house, the ice wasn't colored. This stuff was green, and, as the winter wore on, it eventually cleared itself up. Strange.

ed21
Re: Green ice and icicles on roof

Even though the gutters are clear, are you sure they don't have standing water in them long enough at times for algae to grow.
Over time as the water evaporates then pools again, dried algae could build up and then with the ice damning and runoff the dried algae mixed with the water and dripped out.
If so adjusting the pitch and/or adding a downspout should help.
Just a guess.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.