Ice dam - vaulted ceiling

[Eric Newbauer]

My wife and I have been going out of our minds for the last few days as we attempt to battle an ice dam on top of our three year old home. Since discovering the problem I've read as much on this subject as possible and it seems there is no single guaranteed cure, but that the best strategy for prevention is to ensure adequate ventilation and insulation in the attic. Makes sense... However, my ice dam has formed in a valley of the roof where we have a living room with a vaulted ceiling and a large entry foyer that's approximately 30 ft. high. Obviously, neither room really has an attic.

I'd greatly appreciate suggestions on how we should attempt to eliminate this problem. It's my assumption that I can't realistically do anything to the foyer as far as insulation and/or ventilation. Also, I think I'm limited as to what can be done in the vaulted living room.

I've called several roofing companies. I've even called some electrical companies to get bids on the heat tracing/cabling systems. My problem is that I haven't found much information about preventing ice dams in situations where there *isn't* an attic under the ice dam. With a lack of information I'm concerned I'm going to hire someone who will sell me a 'solution' that isn't really going to help.

[HA HA Budys Here]

Are you certian what you have is indeed a dam of ice, and not just an isolated area with little sun which hasn't melted yet?

If it is an ice dam, from your description it sounds like the dam is where the LR roof meets a perpendicular foyer roof, or a perpendicular foyer wall?

Ice dams are usually formed where snow melt re-freezes. This problem is more typical when the heat is above the heated space and the lack of heat is on the roof's edge. But it can also happen mid-roof if there's a section where heat escapes , melting snow onto a section where heat isn't escaping, where it's re-freezing.

You have to insulate the portion of roof where heat is escaping at a greater rate than the portion where heat is escaping at a lesser rate, or you must make provisions (roof de-icing cable) to melt the dam when or as it forms.

Take detailed photos of where and how the dam forms you you'll know:

-where to place de-icing cable or

-where you lack insulation

Then pick which remedy suits you best.

[RB]

I had a problem like this over a vaulted ceiling also. I have two roof surfaces that drain onto the roof above the vaulted ceiling. The consequence of this is that that roof carries about 3x the water that it would if it were not connected at the valleys on either to the other roof surfaces. My roof had WR Grace Ice & Water Shield applied up to a distance of about 5 feet from the roof's edge everywhere. In the area that collected all of the water the Ice & Water Shield should have been extended up to at least 12 feet to protect against water but it wasn't (my architect screwed up.) My roof is well insulated so snow stands on it without melting for days. That is, until the sun melts it. The snow then melts and water runs down from the top (the sun impinges on the roof only near the peak due to shading by trees) and re-freezes just above the roof edge. The process repeats and repeats over several days and then the pooling of melted snow and ice is occurring above the 5 foot line protected by Ice & Water Shield so it starts to "rain" inside the house. The only solution was to remove the shingles on this roof section, apply Ice & Water Shield over this entire roof section (about

25 feet from edge to peak) and reshingle. I could have put a heater cable on the roof but I don't care for the appearance and it won't do much if the power is out.

RB

Eric Newbauer wrote:

[AJScott]

You point out a very important point that the "insulate well solution" people apparently fail to grasp: You can insulate the shit out of an attic by filling it entirely from floor to rafter with nothing but the best, most efficient insulation known to science, but it's completely useless OUTSIDE in the gutters themselves, where the sun and warming atmosphere is melting the snow on the roof during the day (snow does melt eventually all on it own, even on the 100% uninsulated roofs of refrigerator boxes that homeless guys live in) and then re/freezing the melt water overnight.

The best preventative solution, best of all, doesn't cost a dime and is truly a do-it-yourself thing. All you have to do to prevent ice dams on ANY roof is to keep the elbowed portion of your downspouts free of ice. THIS is where, more than any other place, water accumulates and freezes upon itself -- a built in choke point, as it were. And once it begins freezing there, all the melt water behind it backs up into the gutters because it has nowhere else to go, and that's why you get ice dams.

So -- once you start seeing snow begin to melt at ground level (driveways, stair railings, the deck, etc.), disconnect your downspout at the connection *above* the elbow (for most people, that's the point just below the main gutter hole leading to the downspout) to keep the melt water from accumulating. Makes sure the hole stays free of water/ice re-freezing, too. Most people just poke at any thin ice forming hole with a long pole once it starts to form and it's really thin. Then reconnect your elbow and downspout to their original state once the snow is gone from your roof so the whole downspout can do its job once it starts raining. You'll undoubtedly end up with a major patch of ice right beneath the open spout/gutter that you'll have to dose liberally with rock salt or chemical melt so nobody breaks their neck slipping on it, but an ice dam on the ground won't f*ck up your roof.

Not pretty or glamorous a solution, but it beats the hell out of sticking wires in your gutters, at any rate.

AJS

[Chris Lewis]

According to AJScott :

Adequate ventilation doesn't require an "attic", it simply requires an air gap and air flow from the eave ends up to vents - usually soffit vents and "mushroom" vents or strip venting at the peak.

If there's an air gap between the insulation and roof sheathing, you will probably just need to ensure that the eave ends have venting and a strip vent at the top.

If your cathedral ceiling is "solid" (no air gap betwixt insulation and roof sheathing), the only relatively inexpensive solution is going to be heating wires on the surface of the roof over the eaves. A much more expensive one is to tear off the shingles, lay 2x lumber as another "layer" of rafters, and then sheath it again - providing venting at both the eave ends and peak.

Ice dams generally have NOTHING whatsoever to do with gutters and downspouts. Otherwise, you'd not see ice dams on buildings that don't have gutters. I assure you, ice dams do form on buildings without gutters too - ask me how I know.

It's purely a matter of when the surface of the eaves is colder than the upper roof, and certain temperature ranges cause the upper roof snow to melt and run off (or even rain), refreezing on the eaves _before_ it gets to the gutter.

Even perfectly clear gutters and downspouts will not prevent most classic cases of ice damming. Even heater cables in the gutters/downspouts will not prevent most classic cases of ice damming.

[Chris Lewis]

According to AJScott :

That will come as a big surprise to those who do get ice dams and don't _have_ gutters/downspouts.

[HA HA Budys Here]

AJ that's a crock of shit.

What about ice dams that form 5' above the gutters when the gutters are perfectly clear?

What about homes and other buildings with no gutters to clog at all?

[AJScott]

If it's a crock, post a photo of one.

AJS

[AJScott]

Those would be icicles, not ice dams ;)

AJS

[Chris Lewis]

According to AJScott :

We were too busy mopping up the inch of water on the floor and hacking channels thru the ice on the roof to take pictures. No gutters.

This may suffice instead, examine the first diagram:

That web site is pushing foam as "the" solution, so, the remediation is somewhat one-sided.

This is a better reference:

I quote: "Contrary to popular belief, gutters do not cause ice dams."

The _definitive_ source - general treatise on how to handle roof leaks, final section on ice dams:

Yet more:

In my garage, we had the definitive experiment. The garage has no gutters, but has insulation and vapor barrier, and is occasionally heated.

A few years ago, two areas of the vapor barrier embrittled (UV light streaming thru window reflecting onto ceiling), cracked and sections "fell open".

When the building was heated, hot air went thru the punctures and heated the roof near the bad spots. Surface snow melted and ran to the eaves which were much colder and it refroze. Classic ice dam formed on top of eaves in just those areas, with huge icicles as well.

Fortunately I identified what was happening before water backup was a problem and made sure that the heat was turned off except for very brief intervals.

Last year I repaired the bad sections, and it's been trouble free since.

[Chris Lewis]

According to AJScott :

No, they would be ice dams

[AJScott]

Look, nobody (including me) is going to argue against the benefits of proper insulation (especially in eave cavities) to prevent heat loss thru the roof, which melts snow faster. (Fact that even the best insulation is a moot point once the sun and cold night air starts doing its business is beside the point.) BUT -- fact is, ice dams most characteristically occur in gutters (which you can't insulate), and unless there's 2-3 feet of snow on the roof, ice dams that cause significant damage (6" or more thick) by pushing under the shingles and sheathing and leaking into the structure don't characteristically occur on houses without gutters. They often do, however, on houses with gutters. True as you say, gutters themselves don't *cause* ice dams. They are, however, the #1 facilitator of ice dams.

As one of your cited sources states, providing proper drainage is enough to prevent the problem, which is what I stated earlier as well. Keeping gutters free of debris and your downspouts free of ice clogs, and clearing snow back 3-4 feet off the eaves after a major snow and not letting icicles accumulate along the edge line (on unguttered homes) will prevent destructive ice dams in the majority, if not all, cases.

AJS

[HA HA Budys Here]

I wonder...

If the solution is de-icing cable installed UNDER the roof sheathing in areas where the potential for a problem exists.

[Chris Lewis]

According to AJScott :

The true facts are that ice damming is caused when the roof over the eaves is below freezing, and the rest of the roof is above freezing. Gutters have very little to do with any of that.

When you add melting snow (or sometimes even rain), the water runs down the roof, and freezes/builds up on the eaves _before_ it gets to the gutters. Especially if it has to get through snow buildup on the eaves.

While the gutter can accentuate/accelerate the problem, a severe ice damming problem will happen regardless of whether the gutter is clogged, empty, or completely non-existant.

If there is significant amounts of snow on the eaves, it won't matter whether the gutter is clogged, empty or completely non-existant, because melt water can't get to the edge of the roof.

When you see a house with snow build up on the eaves with the rest of the roof bare, that's an ice dam about to/already happening.

_Most_ of the buildings I see with ice dam problems and consequent water leaks _don't_ have gutters at all.

They're not referring to gutters. They're referring to drainage from above the _eaves_. Not one of those sources makes any significant reference to trying to keep gutters clear.

Okay, if you (can) clear the eaves (of snow and _ice_) consistently _too_, yes, you can prevent ice dams.

Sometimes. But in some weather situations, it can make it worse, because by uncovering the eaves (removing the snow), the roof on the eaves will no longer be insulated by the snow - making it possible for the eave and main roof temperature to be even wider apart.

Having the eaves and gutters clear doesn't mean that you can't get ice build up. If it's below freezing, and melt water runs over the eaves, you will get ice build up _before_ it gets to the gutters.

This further requires considerable active maintenance. In occasionally highly dangerous situations (you want to shovel snow/chop ice in the middle of the night during freezing rain on a third floor roof? Didn't think so).

One snowfall/melt/refreeze (or just freezing rain) cycle that you miss in the middle of the night can completely screw you for the rest of the season. Unless you want to take an axe to the ice. And replace shingles by the wheel barrow load next spring.

It's simply not practical to _rely_ on this for effective protection in any place where ice damming is a frequent occurance. It just damages the roof for little benefit.

Read the CMHC reference.

[Chris Lewis]

According to HA HA Budys Here :

That could help, but probably not quite as effectively as cable on top of the roof - more direct application of heat.

Eave cables are always a last resort. And in order to preserve sanity in your electric bill, should only be turned on when ice buildup is beginning to occur.

Gutter cables will seldom do anything at all. You have to have the heater cable "cut" a channel thru the ice buildup on the _eaves_ so that water can drain out - whether it goes over or thru the gutters (if present) doesn't matter[+] - much.

The CMHC reference I posted talks about a whole host of things that people have thought to try, and whether they work or not.

[+] Icicle buildup over the edge of the gutters themselves is nothing to worry about (short of them ripping the gutters off), provided you can prevent water buildup on the eaves and consequent wall/ceiling/roof damage.

[AJScott]

True. Iciles are harmless, unless one falls off a high place and spears you in the skull. Iciles just mean you have a 6" block of solid ice in the gutter.

AJS

[AJScott]

(snip)

I take this opportunity to point out the obvious: If it's below freezing, there won't *be* any melt, silly rabbit. You speak as if this melt water flash-freezes once it hits badly insulated eaves even before it reaches the gutters. Not so, Sparky. The problems begin to happen when the temps just start getting into the 30-degree area daytime and go back to the 20s nightfall.

The problem with gutterless eaves seems -- when temps or the sun is high enough to cause melt -- to be that a tiny ridge of ice from the melt is formed at the edge of the eave at night when it gets much colder, thereby creating a very thin "catch lip" that remains fairly frozen the following day. The next day, melt water rolling off from the higher elevation runs across the frozen lip -- most of it draining off, but some of it freezing atop the present ice -- and slowly but surely begins to thicken and create an even taller lip that the melt can't flow over. Consequently, the melt water has nowhere to go but back up the roof and beneath shingles and sheathing. Obviously, people with 1-2 feet of blizzard snow on the roof will have higher odds of seeing a severe ice dam problem develop than someone with only an inch or so.

(snip)

AJS

[HA HA Budys Here]

Sure there can be! On a dark roof, it could be 30 degrees but snow is melting (slowly) dut to strong sunlight, and running down the dark portion until it hits under the snow near the eves, or the cooler clear eves themselves (could be shaded by a doghouse window or whatever) Also snow can melt when it's below freezing simply because heat is escaping over the heated portion, but no longer freezing once that trickle of water passes the heat envelope and gets closer to the eves. And that can occur all night long or all day long.

That is an ideal ice-dam condition, but there are other conditions that cause it to happen.

[Chris Lewis]

According to AJScott :

I guess I don't have to ask whether you were born this ignorant. Clearly you're working quite hard at ignoring everything, including the definitive stuff from the CMHC site.

If an building has air leakage into the attic and/or poor ventilation between the eaves and attic (ie: no soffits whatsoever), the eaves will be colder than the main roof. If the main roof is above freezing, and the eaves below freezing, you _will_ have melt of any snow, and drainage down to the eaves.

But some of it will. Especially if there's any ice or snow already there. Especially on shallower roofs. Especially with asphalt shingles slowing down the drainage. It builds up over time.

Unless you want to keep getting on the roof and destroying shingles to keep it clear, resolving the ventilation problem is the only useful solution to consider.

The _worst_ possible time is when the temperature is staying a few degrees below freezing for a long time, but the temperature of the main roof (due to heat leakage) is just above.

A properly ventilated attic will not ice-dam no matter what the outside temperature does. If the attic isn't properly ventilated, it will only remain ice-dam free by continuous (and destructive) active snow/ice removal.

I know what I'd pick.

That's too ridiculous to even comment on.

Nonsense.

With properly ventilated attic/eaves, the snow build up is irrelevant.

On our house, we typically accumulate as much as 2-3 feet of snow on the roof. It's properly ventilated, so there's _never_ the slightest bit of ice or icicle formation, even with gutters 100% plugged with snow.

The ventilation is so good that the snow on the roof lasts a week or two longer than the snow on the ground in the spring and the roof/attic/ceilings/walls stay bone dry.

Except in that garage where the vapor barrier disintegrated in two places. Major ice damming while the garage was heated. Resolution? Certainly not clearing the garage gutters, because it didn't have any. Shovelling the roof? Well, yeah that'd work (at the expense of destroying the shingles), but fixing the vapor barrier was a lot easier, and stayed fixed.

If you wanna come visit, I can take you on a tour of all the gutter-less buildings with water damage due to ice dams. Not because of dozens of freeze/thaw cycles, but because of simple hot roof/cold eave problems.