Seeking advice: Correcting water dam issue


#1

I’m about to embark on getting quotes on my roof (no I’m not a tire-kicker, I just want to choose someone I can trust and therefore I want to have at least a base level of knowledge).

Have had ice dam issues and water entered into house. Roof is a split-level (pyramid hip + gable) on ~40 year old house. Shingles are approx. 12-13 years old and show discolouration (algae from forest behind house?) Underside of decking is showing discolouration as well, probably due to lack of proper ventilation. At one point there was a Bathroom vent venting into attic, but that has been corrected.

After inspecting the attic, discovered insulation touching the roof under-deck, so thermal bridging is likely occurring…and probably the cause of the ice dams in two locations. There’s not that many soffit vents either (two on one side of the gable and one on the other side since the Kitchen is an overhang; and two on each side of the pyramid hip). Currently, square vents are used. The pitch is not that steep (not sure what the actual pitch is), so getting into the attic to install baffles is not possible (and/or certainly not a pleasant task).

Here is what I am thinking (based on reading this forum):

a) Remove entire roof including decking.
b) Cut/install more soffit vents in existing wood soffits
c) Install baffles
d) Install 5/8" plywood (a bit stronger than code)
e) Inspect/seal flashing around chimney
f) Install “water and iceâ€Â


#2

Pictures of house?


#3

I would not Ice and water the entire roof, just the bottom 6 ft, and baffles can be installed and more vents in soffits after bottom row of ply is removed…that is exactly what I did for a customer w/the same style house…also I&W in the valleys.


#4

[quote=“RD”]

**Shingles are approx. 12-13 years old and show discolouration (algae from forest behind house?) **Underside of decking is showing discolouration as well, probably due to lack of proper ventilation.

If discoloration is the only “Shingle Related” issue, have you considered a roof cleaning product to eliminate the algae and other foreign growth? Here is a link to one product I was referred to: roofreviver.com/

At one point there was a Bathroom vent venting into attic, but that has been corrected.

After inspecting the attic, discovered insulation touching the roof under-deck, so thermal bridging is likely occurring…and probably the cause of the ice dams in two locations. There’s not that many soffit vents either (two on one side of the gable and one on the other side since the Kitchen is an overhang; and two on each side of the pyramid hip). Currently, square vents are used. The pitch is not that steep (not sure what the actual pitch is), so getting into the attic to install baffles is not possible (and/or certainly not a pleasant task).

You could have the Smart Vent Intake ventilation product installed as a Mid-Roof application to be above the point where the insulation is in contact with the roof decking. Here is a link to that application:
dciproducts.com/html/midroof.htm

Here is what I am thinking (based on reading this forum):

a) Remove entire roof including decking.
b) Cut/install more soffit vents in existing wood soffits
c) Install baffles
d) Install 5/8" plywood (a bit stronger than code)
e) Inspect/seal flashing around chimney

I would make sure that New Sheet Metal Flashings are included if the inspection during the estimate warrants it.

f) Install “water and iceâ€Â[/quote]


#5

The shingles are 12-13 yrs old, but are they shot already, or just discolored?
The discoloration of the plywood on the inside is almost certainly due to the venting of the bathroom into the attic. Why are you replacing the plywood again?
Purchase “algae resistant” shingles. Only a few $s more per sq, GAF or IKO, both are a decent product.
I differ from Ed on the issue of “closing off the gable vent” but as he points out it is a contentious issue. HOWEVER, baffles, soffitt vent, turbo vent, ridge vent, and vents on the gables all working in conjunction w/each other will probably cause some consternation/confusion.(…you got something against air?)
If you end up having as much ventilation as you indicate then I don’t see a problem with I+W shield on the whole roof.
You say it is a “pyramid” style roof, this being so then the pitch is likely fairly low (unless it is a very small house) and must be accounted for.
Do not remove the insulation. In colder climates warm air in the attic space is a major cause of ice damming due to the melting of the snow when it hits the roof then freezing as it runs down and passes the eave where the cold air hits it, and begins it’s climb up and under the shingles.


#6

Lets not forget insulation. fixing the ventilation problem is only half the battle. Adding insulation will help alot. You will need a R value of 49 for your climate. If you can limit the heat in the attic ventilation will take care of the rest.


#7

Thanks everyone for your advice. Very much appreciated. True professionals.


#8

We had an energy audit done and we were advised that the amount of insulation is fine.


#9

They appear discoloured, but from what I have gathered here, will need to re-roof in order to get the soffit vents and baffles installed properly.

The house is split-level: pyramid hip on one level and gable on the other. The bathroom vent was in the hip attic. However, the discolouration is both within the hip attic AND the gable attic…so black discolouration (mold?) is due to more than just the bathroom vent it appears. Figured it is best to replace all decking at this point.

Was thinking of removing it only to get in and seal off any sources of heat leaking into the attic from within the house. The insulation would then be replaced…or perhaps a spray foam type used.

Thanks for your advice.


#10

Thanks for the response guys.

The reason I was thinking that the entire roof needs an Ice and Water Shield (at least on the gable section) is that at certain times in the Winter, the snow is piled up in a drift that goes up well beyond the bottom six feet of shingles in two areas on the gable. Figure it would be cheaper to play it safe rather than have to pay again for internal water damage repairs that I’m faced with now. Perhaps it is overkill? Is this generally not advised because it may cause another issue (and perhaps void a warranty)? Or is it just not deemed necessary?


#11

I+W shield is NOT a vapour barrier as opposed to 15/30lb felt, therefore it will not allow any moisture trapped under the roof to escape as the felt would do, subsequently some contractors advise against it. Of course, expense is a factor also. Your choice of shingles will answer your question on warranty issues.
The reason I+W shield only covers the first 3/6ft of the roof is that ice will seldom climb that high before it is noticed and dealt with.
The pitch of your roof is directly related to this subject. If it is a low pitch, typically below a 3/12 then you SHOULD encapsulate the whole roof. If it is over 3/12 (south LA, up there it is probably steeper) then you should be ok. Snow sitting on the roof will not leak through the shingles but as I said previously will increase the chances of an ice dam if the attic space is not effectivly insulated. Your concern indicates that you want this done right, so check this issue. Google “CALCULATE ROOF PITCH”.
Very easy.
Good luck


#12

Ice can backup under the shingles.

I+W shield IS a vapour barrier


#13

That’s what I meant to say, “Is a vapour barrier as opposed to 15/30lb felt which isn’t” which if you take the paragraph in context is obvious, Thanks.

Yes ice will back up under the shingles which is entirely my point but SNOW WILL NOT LEAK THROUGH THE SHINGLES.


#14

oh sorry i was just gettin a sip a tea in sunny florida.

gweedo.


#15

OK, so I’ve received two quotes. One recommends 20 feet of ridge vent for the gable roof (side-split house with gable and hip). The attic floor space is 20’x 25’ so 550 sq feet.

Using the NFA calculation (/300, x144) need 264 sq in of ventilation. Using 50/50 rule, that would mean 132 sq in of exhaust. The ridge vent product has a rating of 18… so would need 7.3 linear feet of ridge vent (if I’ve calculated this correctly).

Some additional soffit vents will be cut in to get 6 x 26 NFA = 156 inflow.

Given that the recommended 20 feet of ridge will give 360 outflow, won’t this be a problem with the exhaust being more than twice the inflow?

Roofer #2 quoted 2 normal square vents, but didn’t specify the NFA ratings…so I’ll need to have him elaborate.

Advice much appreciated. I want this job done right…

BTW, Roofer #1 is 60% more expensive than Roofer #2 (and I’m going with reputable companies with 20+ years experience, not fly-by-nighters! Wow!


#16

It sounds like you have more money than you know what to do with.

like your replacing the decking just for fun.

You replace the plywood decking because it is rotten(direct water damage) or because it is too weak to walk on.

And no, do not close off the existing gable vent.

I have a feeling some “lucky” roofer is in Big trouble…


#17

Not “just for fun”. There’s significant mold as a result of a bathroom fan venting into the attic for many years before we bought the house. Also, damage from two significant ice dams. We want the job done right. And done once!

Okay, that’s contrary to the opinion of others on this forum and the manufacturer. But thanks for the opinion.

Not sure what you are implying here.


#18

I have a hard time believing that.
Respectfully, I would need to see it to believe it.

so you replace that particular wood, not the entire roof.
but it sounds like you might be a slight germ-a-phobe
(No disrespect intended)and i understand that and the ONLY way you will be able to sleep at night is to do what you are doing.

So i guess it is a fact then, huh
go ahead and remove ventalation from your roof.
I’m sure it will make it better.
I disagree with most roofers in my area about certain roofing practices.
I dont know if it will be the same in this forum of nationwide contractors.

Not sure what you are implying here.
yeah you do…


#19

It was recommended to close a gable vent to allow the ridge vent to work as designed. The ridge vent and additional soffit vents will increase overall ventilation quite adequately.

Do you always post snarly comments, or am I just a “lucky” poster?


#20

You must close the gable vent if you are putting in a ridgevent otherwise it will create a short circuit sort of deal. If you are really worried about ventaliation being a problem try to find a company that has been certified by the Air Vent Corp. I do believe they are the biggest company regarding that issue and from going through the courses you gain a lot of knowledge about creating a proper air flow. Two square vents will never be enough for a house of your size. Putting in the soffit vents will help the problem dramatically if paired with a continous ridgevent. When we redo the soffit we use vented soffit the whole way though. Probably just a preference although we had a huge amount of icedamming up here in Wisconsin last winter and none of the roofs we did last summer had any ice dams all because of proper air flow. You should run the ridgevent from one end of the ridgeline to the other end. (We go completly end to end because it seems to look nicer). Also, what were in both of the quotes? Such as the materials they were planning on using among other things.

Never I+W a whole roof. One of the bigger companies did that to a roof just a year ago and now the roof is already shot and guess who gets to give them a new roof and fix it. The reason being the icewater does not allow the roof deck to breathe obivously creating more problems. I was also told by a GAF rep that I+W up 6 feet makes no difference in preventing the problem. The only thing it helps is to make them more money. Maybe just another preference thing.

"roof-lover wrote:
I have a feeling some “lucky” roofer is in Big trouble…
and you replied
Not sure what you are implying here.

I am sure he means that he believes you will become a big headache and problem to whatever roofer you decide to have do your house.

Hopefully all my rambling helped something.