I have a house at 10,000’ in snow country with a metal roof. It is not standing seam, but it is the cheaper variety where most of each panel is flat and the two long edges are raised where they overlap (or underlap) the next panel. Screws with rubber washers hold it on. The ridge runs East-West. Most of the roof is very steeply pitched, so snow normally does not stay on it for long, even on the North side. But there is a shed roof dormer (only about 12’ long) on the North side of the house that intersects the steeper roof right at the ridge. The pitch of the dormer is very shallow, about 3 in 12. As a result, snow piles up on this section, all winter long, sometimes as much as two feet high. It melts back slightly at the ridge, since it is exposed to the sun in the South. The ridge is covered with a v-shaped metal vent. I am getting some water and ice coming out of the siding just below the dormer roof overhang. I believe that as the snow melts along the ridge, it pools against and up under the ridge vent until it overflows into the airspace under the roof deck.
I would like to seal the opening (about an inch high) between the vent and roof surface on the dormer side of the ridge. I would think this might stop the water from getting into the house. The roof would still be able to vent on the South side, since that would not be sealed.
Is this a good idea? If so, what do you suggest I use to fill it with? I was thinking about cutting pieces of wood for each opening and then seal them with silicone. But I also thought of just using expanding foam insulation that would be a whole lot easier.
Any recommendations would be appreciated.
Replies
Are you getting any ice build-up at the dormer eave? Your theory about water coming up under the ridge flashing may be correct but then again, it may not.
I live in Faribanks, Alaska and typically the problem we see here is caused by inadequate ceiling insulation and/or poor ventilation. With snow on the roof, a poorly insulated and ventilated ceiling/attic will cause the snow on the roof to melt and run down the roofing until it gets to the eave (which is cold on both the top and bottom) where it will re-freeze. This process builds up ice which, if left alone, can lead to a pool of water forming on the up-hill side of the ice dam. This pool of water will get under shingles and tin roofing and cause problems such as the one you discribed. Adding two rows of Grace Ice and water shield at the eave will help prevent problems from ice damming. This Grace will need to go under your metal roofing. Upgrading your insulation and providing adequate ventilation would also be another option. Something similar could be happening at the ridge but if that much heat is coming through the ridge vent, you've probably got some insulation problems.
I too question whether plugging the vent will work, but it seems to me that there is likely ice and water shiled already in place because if the water is getting in any of the three places mentioned, it is not leaking inside3, but running untill it icicles up at the eave.
You makea good point about the insulation factor contributing to roofs warm enough to create ice dams and leaks, but there is anothe possibility that comes to my mind from memories in high country Colorado where we saw cold as bad as in AK.
That is that if the roof and ridge is inadequately vented, the solar heart striking the south side could be adding just enough heat to rise through sheathing and do some modest thawing of the snow drift on the opposite side. Thus, if the culprit is lack of ventilation, then plugging the ridge vent will cause more rather than less of the same problem.
so, MEPTMORE, are there soffit vents too? how much insulation do you have? let's fix the right problem without creating another one if we can.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Lurch, DanH, and Piffin,
Thanks for your responses. I apologize for not responding right away.
I know the entire roof has ice & water shield (IW), since I saw them roofing it. It also has small (maybe 3") circular vents across the underside of the eave - one in each rafter bay. In terms of building up ice on the eave, it is built up everywhere over the entire shed dormer roof - right up to the ridge vent where it is melted down. Since nothing but the top edge against the ridge is melted, I assumed it was done by the sun rather than heat escaping thru the insulation. I know I have a bit of leakage thru the seams, which shows as a few icicles coming out above the eave fascia between the underside of the metal roof surface and the top edge of the IW. But I am also getting an icicle or two coming right out of the siding several courses below the eave. If I knew how to attach a file, I would send you a picture, as it is pretty bizarre-looking. I had thought about heat tape, but I consider that a last resort, since I will have to install an electrical outlet and it is pretty high up. Agreed, it will likely be the only solution that works, but I wanted to try my hare-brained scheme of plugging the ridge vent (on the North side only) first. Assuming I am stubborn and want to give this a try anyway, anone have any suggestions on whether or not spray foam whould be a good choice. I believe it would seal OK, but I am not sure if it is OK to have it exposed to the weather. Any thoughts?
Have you tried useing a snow rake and cutting, removing the lowest to 2' of snow. This generally provides the the snow room to melt and slide off even shallow pitches which would decrease back up into your ridge vent. Most hardware stores cally snow rakes that are safe on metal roofs.
Unfortunately, the roof is three stories high and I don't even have a ladder that tall. To get up there, I have to climb out a skylight, which is pretty dicy with snow on the roof. As for it sliding off, there are three plumbing stacks going thru that roof which is likely why it won't slide off.
They also sell an electrical heat cable that is laid zig zag along the eve to speed up the melting process. Agian once the first two feet are clear of snow then the rest should come down. Or hopefully the cable may prevent any build up if turned on during a snowfall.
This weekend I will try to see if I can install an outside outlet somewhere near the eave so I can put in some heat tape. It doesn't cost that much, so I might as well give it a try.
Does anyone know how to attach a picture to this discussion?
It might make more sense if you could see it.
I have attached a couple of pictures
Unfortunately the pictures don't show a whole lot at that angle (really need a shot from roof level -- possibly a telephoto from a neigbor's upper story window or a nearby hill), but what I see looks like "normal" ice damming where the water runs down the warm roof until it hits the cold eave.
Did you notice the long icicles on the siding? The just appear several feet down the siding from the soffit. Perhaps it is water running down the inside surface of the roof decking and then running into the wall between the siding and sheathing. I believe I will go with yout suggestion on the heat tape, since I can easily do that from the roof. If that doesn't work, I'll rent a scaffold and tackle the soffit vents.
The icicles on the siding occur because water is backing up where it's dammed at the eaves and working its way through seams in the roof. This suggests that the dam is fairly low on the roof -- ie, "normal" ice damming on the eaves. If the dam was higher up you'd get most of the water on the ceiling. Instead it's running down the inside of the outside wall.
I installed heat tape on that roof over the weekend, so I suppose sometime this winter I will see if it solves the problem. Thanks again for all your help.
How did the heat tape work?
I am having a similar problem here in southern IN where we just got blasted with a bunch of snow. it's not typical for the area so i don't know if i want to make the investment. however, it sure would be nice to know I could do something to prevent the gutters from freezing and causing water to run down the side of the house (and inside).
Also, if anyone else sees this message i would enjoy reading responses...my problem is on the southern exposure of the house where the sun melts the snow...this is an old style home with gutters staight against a gutterboard...no soffit....crown molding supporting gutters.
Cheers
check in the attic and make sure the insulation is over the outside plate
is the house ballon framed ?
Crosscutter55,
The original section of the house is balloon framed. Interestingly, This is where the main problem is.
I can't see the roof plate to tell if insulation is on top. The second story of the house has a 5 ft kneewall. From the attic it appears that there is wood blocking between the rafters where the florr meets the ratfers.
Any ideas on how I can "beat' the melt. I would like to minimize damage if possible. I saw some old threads suggesting snowrakes. I think that will work for the snow of the roof but my gutters and downspouts have ice blocks ready for some ice carving!
Cheers,
Cliff
ice daming is caused by the cold and hot air mixing at the points where the roof rafters meet the plates when the home is framed conventionaly. however the same effect can happen with ballon framing
i am no expert on this but i have exsperinced it on some homes & once the insulation was over the plates ( or solid blocking ) the problem stopped also snow & ice sheild on the roof is another thing that i have done ever since i had the first problem
I lived in Wisconsin for a while and they had a solution to ice dams. When it's coming down you don't have the problem so stay inside or go out in it and blow snow. After it stops you take a long pole and put a light board on it so you can lift it up on the roof from the ground. You just pull the snow off the roof on the south side. It's usually only in a couple of places above windows or where the insulation is thin.
It gives you an oportunity to get out of the house and play in the snow.
Sometimes the simplest solution is a roof rake. Lets you get the snow off the roof, so that it can't melt up there and cause trouble.
Here's another trick for dealing with ice dams.Carefully remove all the snow you can with a roof rake. If an ice dam has started to form at the edge of the roof, take some old panty hose, cut the legs apart, and fill each leg with enough ice melt salt so the sock is 2-3" in diameter. Lay out the legs over the ice dam -- every 2-3 " feet is more than enough. the salt will melt the ice down to the roof, creating a channel for water to escape as it melts. I tried this for a client last winter; it looked pretty odd, but it worked very slick. At least it immediately stopped the interior leak, and there was no apparent damage to the shingles.
You have to keep your roof cold. Venting does this. Sometimes builders use vented drip edge to bring cold air in at the bottom. The vented drip won't work when it's covered with snow. So hopefully you have soffit vent that works from under the overhang and doesn't get blocked.
Once you have cold air coming in at the bottom you must allow it to have a path to run against the underside of the roof (this keeps the roof cold) this path should be above the insulation (which is keeping the heat away from the roof surface) and continue to the top, hopefully a ridgevent, where it moves out. Any warmed air that escapes and
enters this venting path will only help the air rise (as it is warmed) to the top and escape, this process continually pulls replacement air from the bottom- cold fresh air that keeps passing along the bottom of your roof. As long as your roof is cold you don't get melting.
The roof rake is a good idea though, because eventually the sun's going to come out and warm everything up and start melting the snow. When it gets cold again the ice starts to build so when the melting starts again, if you don't have ice and water barrier under the roof shingles the water will back up behind the ice and find a path under the shingles.
Thanks everyone for the comments. I improvised on the roof rake concept and used the brush for my pool which extended 16 feet. Took a lot longer than a couple of minutes though!
I'll work on the insulation/ventilation issue. The debate I'm having with myself is "do I bother to correct something that will only impact the house every 20plus years?" i must admit that i don't wnt to go through that again. Several doors in the house aren't as smooth operating as they were prior to the water getting in.
Thanks again!
Hello:Low rafter heels are part of the problem, very often: because you can't fit much insulation in there -- and even *less* when you put in the air baffles like you are supposed to! The air has to be able to move (by heat syphon) from the soffit vent (or drip edge vent) up the roof to the ridge vent (or to the gable end vents).Ever do this on a hip roof? Where you are supposed to notch the tops of the jack rafters to vent them, one bay into the other, on up to the ridge? Has anybody tried putting "ridge" vent on the hips; at least part way down?Bituthene/Ice & Water Sheild is your friend...Neil
Thanks for the thanks, don't forget though the ventilation isn't just to minimize
ice damns. Hot humid air is also circulated out in summer, dampness from dew
point in winter. So the whole venting issue is about more than ice damns.
Also, fiberglass insulations R- Valur is cut in have if it gets damp.
Hello:Yes, and one of the other major benefits is the lifetime of the asphalt shingles is extended...because they are kept cooler. And the house stays a little cooler, too, if the attic is cooler -- which can ease the load on the A/C, which would lower your electric bill.Neil
Your pictures look like a hip rood with no ventalation in the soffit is this the case? When you have that kind of ice build up I would look at the air flow in the attic space, does this happen every winter?
Excuse me, on further examination there is venting in the soffit but I don't think it is enough. On my hip roofs, if this a hip roof, I have continuous vented vinyl or metal soffit.
If you have ice building up over the entire roof, that's your problem. It sounds like heat from the inside is melting the snow, due to a lack of ventillation.
I am considering putting some of that 2" foam board on the inside surface of the sheetrock ceiling and then covering that with T&G. Perhaps that will add enough insulation to help avoid the melting.
It'd be surprised if that fixed it. Ventillation between ceiling and roof, and sealing air leaks from conditioned space to "attic" are the real "biggies" here.
OK, I am confused. Several of the posts indicated inadequate insultation might contribute to the problem. So why wouldn't more insulation help?
It's not insulation per se, it's the leakage of heat from the "conditioned" space up into the "attic", warming up the underside of the roof.
I would presume that the ceiling in question is already insulated to a reasonable degree (eg, several inches of fiberglass on top). Adding another inch or two won't make much difference. At this stage there's probably more heat "leaking" into the "attic" area via gaps along the tops of stud walls, wire and pipe penetrations, etc, than is coming through the insulated ceiling.
Also, once a modicum of insulation is in place, and the worst penetrations are sealed, improving ventillation (to get the heat out of the attic) will likely be more effective than just pouring on more insulation.
Maybe a continuous vent along the eave instead of the small circular vents would help
Heat escape and lack of required ventilation is the cause of your problem.
You don't have to be a rocket scientist to calculate the needed amount of ventilation required. Usually with a roof pich of more than 2/12 , you need a minimum of 1 sq ft of vent for every 300 sq ft of attic floor area. 2/12 or less requires approx 1 sq ft for every 150 sq ft of attic floor area.
The calculated total is split 50/50 between incoming(soffit) and outgoing (ridge)air
Those 3" circular vents that you have are pulling in about 7 sq inches ,LESS the restriction of the design louvres and the small screen (if any) that boils down to less than 4 sq inches of "free area" each. Thats hardly no air at all. At that rate, you would need approx 40 of them in order to obtain just 1 sq ft of incoming ventilation. The ridge vents are calculated the same, so many sq inches to the linear foot. (less the restricted area)
btw, is your attic area floor level well insulated to eliminate any air escape?
And if it is, you can never have too much soffit and ridge ventilation
(but as you know, you can have too little.)
It is a bathroom and closet under this shed dormer roof, so all of the space is heated.
OK, my math is pretty rusty. But if the area under the shed dormer roof = about 150 square feet of floor space. So I guess I need 1 square foot of ventilation split between the ridge and eave. I don’t think the ridge is a problem since there is a continuous vent, but the eave has only 8 circular vents, and I believe you are saying I need about 20.
I doubt that plugging the vent will work. If the ice builds up high enough to be over the seams between panels, water will leak through the seams. (It will also leak around the washered screws, if the "head" is high enough.) I suspect that this is the more likely path the water takes, not up through the vent.
Plugging one side of the vent might help, though, by preventing warm air from inside from melting the snow. But likely, as you say, the sun is doing the lion's share of the "work" here.
It might be that heat cables are the only viable solution, unless you are up to removing the snow regularly.