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Question DetailsAsked on 1/9/2014

Hi I have a ranch with a hip roof over hang about 3 feet vented soffit all the way around getting frost on the ply

Hip roof soffit vented all 4 sides getting frost on plywood outside temp dropped to -8f will a ridge vent help insurance company said I need one will not cover damage

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6 Answers

Voted Best Answer

If soffit vented, where is the outlet - a true full hip roof does not have gables where endwall vents could be, so if ventilation air comes into the eaves, where does it go out ? Maybe this is your problem - without ridge vents there may be no airflow through the attic and underside of the roof, hence frosting and condensation. A simple roof vent or spinning ventilator or two will not provide enough airflow to ventilate an attic. You don't say what damage you have, but yes you need ridge vents or active ventilation - ridge vents almost always better if you can do them.

You say 3 feet vented - do you mean soffit vents 3 feet wide out from the house all around, or only for 3 lineal feet on each side. If the former good, if only 3 lineal feet per side not anywhere enough.

Now a practical note - at -8F, almost all attics will have some frost on the underside of the sheathing - a light coating, not a heavy buildup. If a heavy buildup 9more than 1/8 or less) or it is leaking into the house when it thaws out, then you have excessive moisture getting up into the attic - almost always due to penetrations (around pipes, vents, drywall gaps, attic hatch, etc) so that needs to be solved or you may still have a problem in the future, with possibility of mildew and mold, framing rot, etc depending on how much water and how much ventilation you have.

Insurance company will not cover because it is considered a pre-existing condition and long-term damage, not a one-time event.

Your best bet is to get an energy auditor or architect or civil/engineer who does residential design to take a look and evaluate your situation (probably about $150-250), and determine what you can do to solve it.

Also - here is a discussion today on sheathing underside foaming that might be of interest to you (I do NOT recommend this, but someone may, even though it would do nothing for your issue) -

Also, one on possible frosting or condensation issues that might be applicable -

Answered 6 years ago by LCD


LCD's answer is correct but I have one question.

Is this a new thing that you have noticed do to the cold snap that much of the nation has had. Actually I just heard every state in the country had below freezing weather including the top of a Hawaiian volcano. If it is a new occurance it is most likely just the cold pulling out the moisture in the wood. All wood products absorb moisture from the air and that is why some doors will swell and stick durring damp weather. If you do not see any water stains on the plywood (other than those that might have happened durring rain when being built) I would think this is what it is. You probably are going to have to add a few powered or passive vents just for saving on cooling costs and to increase overall ventilation. Most likely if you just called the agent about this they were not knowledgable about construction just as I have to rely on my agent for insurance issues.


Answered 6 years ago by ContractorDon


Don talked about fresh water stains versus ones from exposure during construction before the roofing was applied - you might question how to tell.

"Original" stains, in a house tht has afed for at least a few years, will blend fairly well into the wood, rarely have distinct boundaries, and generally be a shading difference but not a dramatically different color, have a dark black or very deep brown border, or hae raised grain unless it was left exposed for a long time before roofing.

Fresh stains will typically not have faded at all, so they will have distinct dark borders, might have mildew or mold on them, will typically feel softer if you put your findernail into them, and if due to extended or repeated wetting will typically have raised grain or splitting of the surface laminate.

Don's comment on the recent cold snap is on the mark - that is what I meant when I said most houses will have a frost layer at subzero temps - not only does moisture come out of the wood due to vapor diffusion from the maybe 15-30% moisture content wood toward the extremely low humidity in the cold air and then frost on the surface, but even small amounts of moisture coming up from the house through gaps and penetrations will frost onto the underside of the sheathing and the top of the insulation because it freezes to frost as soon as it hits the cold air.

Unless you have a thick enough buildup to drip onto and wet the insulation when it melts, have it running down the underside of the sheathing and rotting your soffits and fascia board, or have frost all over the interior of the attic, while it is certainly "undesireable" it usually does not cause lasting damage, except to anything you might have stored up there. In very cold areas - upper Great Lake states, North Dakota and upper Montana, and much of Canada and Alaska this type of frosting occurs every year. As long as it does not constantly wet and dry the wood, but rather occurs in fall and lasts till spring or only occurs during extreme cold snaps as is likely in your case, I would not worry unduly about it. BTW - frost like this can cause a light cottony thin layer of mildew on top of insulation, ESPECIALLY on top of blown in cellulose (my main beef with using cellulose) as it supports mold growth (being an organic material)- if this is not persisent into the warmer seasons and does not involve mold growth or rot of the wood, it is not a good thing but also not catastrophic, and normally nothing is done about it. Of course, if this happens, you don't want to be waliing around or working up there without good respiratory protection, and of course your clothing should be immediately washed after such activity.

As far as minimizing the frost - 1) ventilation for the attic (preferably ridge vents in your case, but forced ventilation at the peak worke pretty good in hip roofs too, because all the air is flowign to a shorter ridge than in a normal peaked roof house), and 2) getting any gaps in the vapor barrier (continuous heavy plastic sheeting that should have been applied to the bottom of the attic floor joists before the sheetrock ceilings were put up), all penetrations (around wiring and electrical boxes, ducts, fan boxes, light fixtures, and pipes), and any leaking exhaust ducts sealed up to minimize the amount of moist air making it into the attic.

Answered 6 years ago by LCD


I don't know how long the ridge is on your hip roof but most homes around here with a 4 sided hip design don't have much of a ridge so you'll likely have to look into other forms of vetilation at the top of your roof. Code varies from region to region on how much ventilation you should have. I'd imagine it is a lot less in your area than ours in Texas. Consult a general contractor or insulation contractor with knowledge and experience on this issue. Also, your utility company probably has someone whose job is to advise people on energy savings, which this also falls under. Their services are often free.

Answered 6 years ago by Todd's Home Services


Thank you for the info I live in Connecticut no leaks in warm weather. Had the house for four years never seen a leak Had a roofer come out today said I had two layers of shingles and no paper down also said need to vent the ridge and pull back insulation from soffits thank u guys or lady's again big help

Answered 6 years ago by Jager77


Two layers of shingles is not inherently bad, assuming the second layer was put on because of aging of the first layer, properly applied so they lay down flat and are not all warped and deformed, and was not put on to cover up significant leaks. No paper means no tarpaper (roofing felt) or roof underlayment under the shingles, so you have no protection over the sheathing (plywood) if you do get leaks through the roof, or more commonly around roof penetrations first. Not fatal, just very bad construction practice, and means your roof is likely to leak here and there (maybe not dramatically) before the shingles age out, as water seeps down through shingle cracks, nails, etc. and does not have an underlayment to carrry it down to the eave edge of the roof. The double layer actually helps you here (maybe why it was put on ?), because any first layer leak has a very good chance of running back out to the roof surface on top of the first layer before it can reach the sheathing.

When I say not dramatically leak, many times a small roof leak is not a major problem unless it rots the sheathing, especially if not at a penetration. Leaks at duct and pipe penetrations tend to run right down the duct or pipe, and pretty much directly into the house. They also tend to be larger than leaks due to cracked or isolated missing shingles or leaking shingle nail holes. Shingle leaks that do penetrate the sheathing (usually at sheet joints) commonly do one of two things - if large, or if small and run down the underside of the sheathing then hit an obstruction like a sheet edge or a rafter, they can drip off onto the insulation; or if small can run down the underside of the sheathing, held to the underside by surface tension so may drip a bit along the way or not drip at all, run down to the fascia and then down the back side of the fascia, typically rotting it and the fascia edge and any wood soffit. Of course, if there is bug screening at the eaves that stop the flow, then it drips down that - either outside the wall, or down into the wall if it terminates

Minor drips (a quart to a gallon size per rainfall, maybe) commonly get largely soaked up by the insulation, and if larger can pool on the vapor barrier on top of the ceiling drywall, but if small may dry out after the winter or after the rain stops and never even be noticed, escept for maybe a bit of surface white or gray mildew. Larger leaks, of course, will come out somewhere - usually first noticed as ceiling drywall staining, staining at the top of a wall, or by coming down through a light fixture in the ceiling, depending on where it comes down into the insulation, and where the closest exit point is to the low point of the vapor barrier or drywall sheet it comes onto lies.

Sounds like the roofer who came out was honest with you and did not try to upsell you on a new roof automatically. If your insulation is blocking the eaves, like it sounds like he saw, there is no way airflow can get up into the attic. Therefore, this needs to be held back - with eave baffles or air scoops (or lots of other names) - here is link to images showing baffles and how they work -

Then, as discussed before, you need a way for that ventilation air to get back out of the attic - ridge vent (there are extra large opening size ones and also ventilation celestories designed for short gables), can do ridge vents at the peak and also along the top part of the gabled ridges like this, -

or even ridge vents combined with a cupola with all-around louvres to let the air out but keep rain/snow out - like this

One suggestion if you do a cupola - the baffles or louvres, if open enough to actually provide good ventilation, let some rain and snow in - so I suggest one of two things - double-layer baffles or louvers with drainage to the outside over waterproof materials (like plastic) between the two layers to intercept blown wind and rain and drain it right back outside (preferred method); or putting an open-weave woven geotextile inside the cupola, standing clear of the inner surface, leading down to a deliberate ice and water shield drain pan around the inner base, and leading off under the coupola bottom edge onto the roof, to drain off any water that comes in through the louvres. This is more common in Europe, probably starting as an easy retrofit to existing cupolas. Makes for sort of an air-permeable shower curtain effect. Will NOT work in very cold climates, because will frost up solid. I have also seen people cover the inside of the louvres with poly mesh drainage mat (looks much like the mesh-type roll-out ridge vent material, which would also probably work if spliced wider), draining right back outside under the louvres. The key is to keep wind blown rain from coming in the louvres and right down into the atic, like happens with most brands of roof turbines, passive roof vents, and similar devices.

Also - before thinking cupola, check zoning/land use regs - many limit building height to normal 2 story house height, and would require a variance for a cupola. Cupola cost around $500-700 installed for prefab fiberglass or plastic (best), or $1000 plus if wood (not so good, due to weathering and rot and frost accumulation issues).

Thought on cost - eave insulation trough/attic baffle installation, assuming normal doable (but never fun) access - about $10 each installed if being done along with other work by same contractor. Ridge vent about $5-12/LF - decent brands, rigid type (not roll-out mesh junk) typically close to $10/LF when all is done.

Answered 6 years ago by LCD


Here is something you may have missed that I have found on a lot of roofs in the Chicago market. Do you have a exhaust fan in you bathrooms? If so where are they vented? Several homes have the exhaust fan blowing into their attic and most homeowners don't have a clue. This is one of my check list items when I sell a roof to inspect roof deck and proper ventilation of the bathroom exhaust fans to go through the roof deck or side wall. If your bathroom vent is blowing into the attic every time you take a shower the steam is blowing into your attic. The steam would then freeze and coat the roof deck rafters and anything else that is in the attic with ice or frost. So please check this to ensure you don't fix the wrong problem and then have to fix it again.

Next - Where does your insurance company say the don't owe for damages? Your insurance company owes for direct physical damages that occur per event. So if you have ice in your attic and that has thawed causing damage to the house or personal property then they owe for that. How ever they do not owe to fix the problem unless it occured during the event like a tree branch feel in the same event causing snow and ice to enter the attic.

It's like car insurance if you are in an accident and someone hit your car they only owe for what was damaged in that accident. So if your car had a small dent or rust spot right next to the new dent the insurance company is not responcible to fix the old rust or dent just the damages occured in the accident.

I hope this helps trouble shoot your frosty attic, and helps with the insurance company.

Best of Luck

Richard Jeziorski

Liberty Roofing & Siding Inc.

Answered 6 years ago by LibertyRoofing

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