Iced over and leaking porch roof

[Adkjake]

Maybe I should have left well enough alone. Had no problems last winter, (1st year in the house) but a few weeks ago, after several heavy snowfalls piling up,
I shoveled off the low pitch roof over the porch. There was 16 to 18 inches of snow on the roof. This is an unheated porch, used to be just screens, but last fall I enclosed with vinyl windows and doors. The other day after some additional snowfalls and some thaw - freeze cycles, it iced over, and with the thaws started leaking like crazy. There was a 2 or 3 inch deep ridge of ice a few inches wide where the steep roof meets the porch roof and another one at the drip edge. The whole roof, including the porch is architectural shingles, only 4 years old.

Come spriing, I"m thinking of taking the shingles off the porch and putting down rolled roofing, and leaving it alone over the winter. Hell, the house has been here 30 years thru many winters and the porch hasn't caved in yet, no sag at all in the beams or floor. Would this solve my problem? If not, suggestions? The pix below should give a better idea of my situation.

 

[semipro]

I'd suggest you consider putting a self-adhesive roofing membrane on the whole porch roof. Grace is one manufacturer. Whatever roofing you chose goes over that.

 

[peakbagger]

By the looks of the pitch, you are far below the minimum pitch for a shingled roof. A DIY fix is to strip the porch roof as well as 3 or feet up the main roof , install WR Grace ice and water shield and recover with shingles. The shingles act as UV protection for the Ice and water shield. Alternatively have a metal roof put on.

 

[Adkjake]

Wondered about that. How would you transition from the shingled main roof to the metal roof on the porch?

 

[Hogwildz]

Agreed. The pitch on that porch roof is way too low to shingle without Ice & Water shield.
If you want to do the metal, I would still Ice & water shield underneath. The metal roofing can be terminated to the upper roof several ways.
1. Bend the panels about 1' to 18" to follow the pitch of the upper roof. With the ribs this can be difficult.
2. Make a proper channeled flashing the top edge of the metal roofing would slide into, you would seal the end to the channel real well with a good caulk like urethane caulking. The a counter flashing would extend about 18" up the steeper roof, down onto the porch roof about 1' or so. This is more complex, but more proper detail to flash the transition.

You could also cover the porch roof with fully adhered rubber roofing and merely extend it up the steep roof 18" and shingle the steep roof back in over top(you will have to do the last step of shingling back in no matter what you do).

Roll roofing is garbage, I am warning you right now you will regret using it. Its is at best used for sheds, and does not last long.

 

[Adkjake]

Hogwildz, thanks for the advice. Sounds like you know more than a little bit about roofing. Do you think I might have created the problem
by shoveling the snow off that section in the first place? Like I said, its been there 25+ years, thru some heavy winters, and it is solidly built.
It's only an 8ft run for the rafters from the header over the windows to where they meet the main roof. 2X8s, 24" on center, 4X4 framing.
The roof faces northeast and has several white pines towering over it, so gets no sun. Maybe I should have left the snow and the natural
insulation it provides.

I'm with you and others on putting down ice & water shield, but why so down on rolled roof? I've had it on my lake cottage which has a similar
porch roof, and knock on wood, no problems. And it sits on plain old felt paper. Problem location too, as this section of the porch is overhung by
big cedar trees, we're constantly trimming them, sweeping off needles and twigs, and cleaning moss. Has held up so far.

There area number of houses in the area with similar construction, think I'll talk to some neighbors on what they have on the porch roof, and if they
shovel or not.

 

[Reggie Dunlap]

I'd fix whatever is causing the ice dam before tearing the roof apart. All shingled roofs will leak when water ponds behind an ice dam, especially on a shallow pitch like yours. The new roof is just as likely to leak as the one you tear off. Grace ice and water barrier may help some, but how do you know it's not already under there?

You have an ice dam because heated air is melting snow on the steeper roof. The dam forms at the intersection of the two roofs because the (unheated) porch roof is colder than the main roof.

If you are going to fix anything fix the cause of the ice dam instead of masking the symptoms. To do that it looks to me like you need more, or better, insulation in your roof. The upside to re-insulating is lower heat bills and a tighter house. The downside is it may be expensive.

Corrugated metal roofing will leak just like shingles if enough water backs up. The water finds it's way through the panel overlap. Rolled roofing may be better if the seams are sealed very well, but I rarely see rolled roofing last very long. Rolled roofing has mostly been replaced by EPDM rubber membrane on shallow pitches.

Yes, your porch is probably too shallow for shingles, but they are already there and they are not the cause of your leaks.

 

[Adkjake]

The house is pretty tight and well insulated. Plus, because of how it is built, can't really add much insulation. If you look at the first pic, you'll see there is no attic. The top floor is two bedrooms. There's about a 3 foot high knee wall built at each end where the slope comes down, with a 3 or 4 foot wide crawl space behind it. There's six inches of pink inslulation between the rafters and tounge and groove ceiling, also under the floor in the crawl space.

The knee wall is just particle board faced with paneling, I could insulate behind that, would that help?

 

[Reggie Dunlap]

In this climate even 12 inches of fiberglass isn't enough to prevent some melting on the roof. It's almost impossible to install fiberglass with no gaps or voids, and this let's heat out to melt the snow on your roof.

With a second floor cathedral ceiling it's tough to access the rafter bays to re-insulate. To do it right you need to remove the sheetrock and use spray foam. Or you could use fiberglass with 2" Celotex sheets over the rafters. Either way will give you a high R value roof with no air infiltration. Cost will be roughly the same if you hire someone to do it. And your heat bills will go way down.

The point I'm trying to make here is that if you are going to spend money to fix the leaking problem spend it on insulation, not on roofing.

 

[seige101]

The knee wall is just particle board faced with paneling, I could insulate behind that, would that help?

If i am reading that right and my crude diagram on the picture there is no insulation behind that knee wall, that would be a major cause of the ice dam, heated air is escaping right into your crawl space and causing that roof melt whatever snow/ice is on it. The water is then freezing when it hits the cold porch roof. Insulating this wall would help significantly!

 

[Adkjake]

Good job, that's pretty darn close to where the wall is. Should have done that in my post. I checked the crawl space this morning, it was -3* here this morning and I wouldn't say the crawl space was especially cold. There are a couple of rolls of leftover insulation in the space, I will have at it.

 

[Reggie Dunlap]

There are two ways to insulate the space behind the kneewall. Probably the best way is for the roof insulation to continue down to the floor plate. This way the actual kneewall doesn't need to be insulated. If insulated this way that area should be warm.

Or, the kneewall and the floor below are insulated. In this case that area should be cold.

 

[Hogwildz]

Adkjake, Yes I roofed for a living for 13 years. Done everything from cedar, slate, hot, torch down, rubber(EPDM), metal, and even old craft styles such as copper and hand form old school standing seem terne-coated.
A roof can appear to be installed completely perfectly, but be missing a crucial element as in your case most likely missing ice & water shield, and have ice damming & leak problems. Other are poorly installed and have anything from obvious flaws to hard to find leaks.
If it was properly underlayed with ice & water, it would not be leaking, period, I don't. I don't care what anyone says. I'll bet if you take those shingles off, it has nothing but felt(tar paper) or nothing.

If you did not have problems in prior years, with similar amounts of snow load, I suggest checking for any damage or holes you might have accidentally created when you shoveled the snow off this year.
Again, if it was not leaking in previous years, and just started this year, obviously something has changed. If the roof is old enough (forget if you said how old it is), it may finally be deteriorating to the point of leaks starting to show up. If fairly new, then you best check for something caused by shoveling. Regardless, that low slope a roof should have been completely covered in ice & water shield. Years back, before I ice & water shield, we would have to shorten the courses down to 4" exposure. the extra overlap was required by the manufacturers back then to obtain warranty. Sometimes this worked, other it didn't. Soon thereafter, they stopped warranting any pitch under a 4 or 5 I think it was. Most common is a 6 to 9. But the older homes had very steep pitches. As do some new ones these days.

Roll roofing is just not good for the house you live in. I have torn many many squares of this crap off, and it always deteriorated at a more rapid rate then shingles or any other form of roofing.
Back in the 80's it was popular to lay it in valleys and leave open valleys(shingles not overlapped or weaved, kept about 6" or more apart), as it could be had in colors matching the shingles. Problem is, the valley roll roofing would fall apart & crack and leak like crazy. My parents let the builder that did their house use the crap, and guess what happened? Yeap, same as it always does, cracked, split valley roll roofing now letting water leak into the valley and all along the house inside as it ran down. If there is felt underneath, it may not leak for a lil while, but eventually it will.
This is why I am strongly against roll roofing on a house, it truly is garbage as far as houses go. Sheds, cabins, etc? sure why not. Still won't last long. You won't get no 15, 20 years out of it. Doubt much more than 5 to 8 yrs before troubles start in some cases.

Bottom line, ice & water under there, then anything can be put on top and it will not leak whether it dams or not.

Not easy to tell if ice and water under near the transition without pulling a few shingles.
To check at the eave is easy, just lift the last course up and look underneath. Bet you find only tar paper or less under there.

 

[Reggie Dunlap]

Hog-I agree with most of your points. I'm a builder in an area with a lot of cold temps and deep snow, perfect conditions for ice dams.

These days we usually cover the entire roof with ice and water shield, but I still look at it as the last defense. I've seen it leak. Think about it, it's got nail holes through it every 12 inches from the shingles above. Yes it's supposed to seal around the nails but it doesn't always work like that. If he's going to spend the time and money to tear the roof off to install ice and water he might as well use that money to fix the insulation that is causing the problem in the first place. It doesn't leak when it rains, only when there's an ice dam.

I've also seen new, perfectly installed shingles leak from ice damming. Especially on shallow pitches. When you have an ice dam a foot thick there can be deep water behind it. Shingles just aren't designed to keep out ponding water. Ice dams create an unusual situation where water actually moves uphill as the dam grows. All roofing materials other than EPDM are designed to shed water as it travels downhill.

I've done all sorts of things to prevent leaks on tricky roofs. Like you I've shrunk the exposure down to 3-4 inches. I've put 16" strips of ice and water shield on over every course, as well as over the sheathing. They all help prevent leaking from ice dams, but proper insulation prevents them from forming in the first place.

Another thought here is that the leak is probably happening on your upper roof, a few feet up from the intersection with the porch roof. It's not getting through your ceiling till it gets down to the porch. Maybe there's a course of ice and water above the porch that doesn't overlap the porch shingles properly?