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Question DetailsAsked on 10/4/2014

Are soffits needed to fix an ice dam problem?

I have ice dams forming on several areas from the roof. A ranch built in 1940s, there are no soffits around the house, but there are a few vents on front and back of house. The brick is being affected. The contractor suggested putting soffits for ventilation in these areas. The attic also has very little insulation. The other contractor suggests putting an elecrtic ventilation system in attic. I also have a back porch roof, not flat, but not much slope. One contractor wants to put a rubber roof. The other contractor suggests a polyglass type roof that squirrels and racoons won't chew. I live in a large wooded area. Please advise. Thanks

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2 Answers


In a soffit less home a continious roof mounted soffit vent near the bottom can be installed. Put a ridge vent at the top of the roof to allow air to escape, and you will almost certainly solve your ice damming problem. Adding insulation to your areas reccomended level is also a great idea, In Omaha it is an R40, you call your utility company to find out same and get a referal for a ventilation contractor for the non soffited roof. If your attic is finished they now sell foam insulation that can be retrofitted into existing cavities. On the porch for a less than 3/12 pitch an edpm rubber or even better a standing seam metal roof (sold at Menard's etc) would be a great and less expensive idea.

Jim Casper Old Weatherizer and Gutter Cover Contractor

ps see my blogs for ideas if you do not want to clean those pesky gutters


Answered 5 years ago by jccasper


When you mean soffits, I think you mean eave vents - open screened gaps in the spaces between the rafters at the top of the house walls. Soffits are the horizontal decorative (hopefully vented) panels that conceal the underside of the roof overhang like the first picture in this link -

The second picture with the open rafters shows eave vent holes in the blocking between the rafters, which hopefully would be insect screened. Depending on the earthquake, fire and wind/hurricane codes in your area and the types of roof trusses you have, sometimes you can reduce the blocking heights, drill holes in it, replace it with open spaces with metal brackets to brace the rafters - you will need a structural engineer to tell you which can be done in your case if you do not have substantial open space at the eaves now.

Soffits reduce the airflow through the eaves and out the ridge vent (the most effective energy-economic attic ventilation method) and from a building health standpoint are a bad idea but many people want them for appearance purpoes, so in that event they should have the maximum open space possible, with insect (and fire if recommended) screening. Because the openings in soffits restrict air flow quite effectively, the total open area should be farmore than the eave vent / ridge ventopen area so they do not unduly restrict airflow into the attic.

Soffits related to roof icing can work either way - in situations like I have with a significant sun exposure under the roof overhang, just the sun shining on the wall can create substantial winter and spring heat that then rises up under the overhang and melts the snow, causing icing on days when the ari temp is quite cold and also when the sun leaves that area every day. In that case, soffits, especially if angled upward toward the outer edge, can deflect some of that heat and actually make for less roof melting. In general however, they restrict airflow so you get less cool air being drawn into the attic as the hotter attic air goes out through the ridge vent by convection, so in general they are a detriment rather than beneficial in this situation.

The primary reason for roof icing is excess heat coming from the underside of the roof - usually via air leaks into the attic or inadequate attic insulation. You can find a ton of comments on attic insulation and heat/moisture control in the Home > Roofing and Home > Insulation links in Browse Projects, at lower left.

It should be noted that in some cases roof icing cannot be economically prevented, only controlled and maybe drained by using thaw cables, because there are instances like the solar heated wall I mentioned, long winter sun exposure south or west exposures that thaw during the day just from the sun and then freeze at night, very long roof runs where any water falling or forming at the top freezes in the snow pack before it reaches the gutters, and conditions where frequent alternating freezing and thawing days or rain on thick snowpack cause icing under the snowpack on the roof, so in may cases it is a case of mitigating rather than stopping the problem - the main reason ice and water shield is required by code at the lower edge of the roof in snow climates.

In your case, since you say the attic has little insulation, I would say your prorities should be effecting eave ventilation (if feasible - you can provide photos of eave area from outside and also inside attic if possible using the upper left yellow icon above the Answer box in Answer This Question below your question) if you want an opinion on this from the contributors here (and you might also say what area of the country you live in); and adding insulation in your attic once all penetrations from below are sealed off.

It may well be an energy audit by an Energy Auditor and insulation design would be in order for you to determine a optimum insulation arrangement, because it is possible to overdo it both from an economics standpoint and it is also possible to cause moisture problems in your attic insulation by over-insulating.

Answered 5 years ago by LCD

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