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Background: A bay window has been having ice dam issues for the past couple of years. I think the water is coming in through the space between the gutter and the fascia. That space is just on the inside edge of the bay window. I see water dripping from that space on each side of the bay window, so I assume it must also happen inside the bay window.

I still can't tell the dripping only happens during winter melt, or also during rain storms. I seem to hear "tick tock" water dripping during rain storms as well, but it's hard to tell, and there does not seem to be enough to cause water damage inside. I got insulation added to the attic, which perhaps improved the ice dam issue a bit (or maybe it was just the weather this winter), but there was still a bit of water dripping from the bay window frame inside the house.

2 winters ago, when the ice dam issue was at its worst, there was a bit of water damage in the kitchen ceiling, which is more or less at the same height at the base of the bay window.

bay window with unvented soffit underneath bay window with icicles

I am getting the siding redone around the bay window (to add flashing at the top of the siding and bigger flashing at the top of the window, which will hopefully prevent water from coming in). Also possibly add insulation (its always cold around that bay window area in the winter). The soffit under the bay window is currently unvented (as shown in the picture). The contractor said there is no need for ventilation there and they usually install unvented soffits.

Question: Should I get vented soffits installed, so that water has an easy way out (instead of going towards the kitchen ceiling?) Could that cause issues, or even if vented soffits do not do anything, they at least won't do any harm?

  • It's difficult to tell from the photo, is the top of the bumpout against the soffit above? Based on the photo, it looks like water is getting behind the gutter. This could be because of ice dams, improper gutter placement, or missing/poorly installed drip edge. – Tester101 Apr 27 '16 at 15:18
  • Draining water through a soffit is treating a symptom. The disease will be rotting away your home, meanwhile. Fix the water problem. – isherwood Apr 27 '16 at 15:57
  • @Tester101 Yeah, the contractor will look at installing / replacing drip edge. Could you please elaborate on how improper gutter placement could cause this, so I have another thing to ask? – Jimmy Apr 30 '16 at 11:35
  • @isherwood One theory about the cause of the ice dam there is that there is heat escaping from the poorly insulated bay. Once the siding comes off we'll make sure there is proper insulation. But vented soffits at the bottom could also help the bay remain cold, thereby also reducing the chance of an ice dam? – Jimmy Apr 30 '16 at 11:37
  • @Tester101 Yes, the top of the bay is right against the soffit above it. I'm not sure it's even possible, but would it be a good idea to have a bit of a sloped roof put on so water dripping through soffit (or from behind the gutter) slide down instead of inside the bay... – Jimmy Apr 30 '16 at 11:42
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Vented soffit below the window will allow air in, and will reduce the effectiveness of insulation. Other than that, it wouldn't cause a problem, but you're already concerned about the cold near the window.

You should focus on how the water gets in, and prevent that from happening in the first place. It should be fairly easy for your contractor to tell what's been happening once the siding is off. It's hard to tell how things were flashed around the window from your pictures, but it doesn't look like how I'd have done it.

When you have an ice dam, the real concern is water being pushed back up under the shingles. If that's happening, water could be dripping down the internal structure, and vented soffit below the window wouldn't help anyhow. Again, it should hopefully be easy to tell once the siding is off. If you haven't already, mention the water in the house to your contractor, and show them where you've seen it.

  • The ice dam only seems to be dripping in that bay window, so I'm not sure it's actually going under the shingles. I looked inside the attic during the ice dam and there seemed to be ice between the top of the fascia and roof. As far as I could reach towards the edge I couldn't feel water on the underside. I'm hoping installing (or fixing) a drip edge will resolve that. The roof is 3 floors up, so it's not easy for me to look from the outside :( When estimators come for the job they never seem to want to go up a ladder, so they just look from the bottom and guess. – Jimmy Apr 27 '16 at 15:53

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