Roof Ice Damming

[DRH]

Originally Posted by Blue Thunder

Just as a clarification and not really adding to the good advice above, the "bituthene" being referrred to above is lovingly referred to by contractors as "B*tchaThane" because it is a b*tch to work with. It is an extremely thick and sticky, on one side, rolled membrane that nearly all roofing contractors use these days when roofing. W.R. Grace was one of the first to come out with it in the 80's and it is on the shelf at Home Depot and Lowes as "Ice and Water Shield". It comes in rolls that are 3 feet wide similar to felt paper.

In my own personal case, I had my roof done in the mid 80's and we used this product. The standard back then was just to do one layer/run 3 feet up from the eaves. Now a days I see many roof jobs where this product is used the whole way up the roof and I opted to do this myself when I had my roof done again this past summer.

BT

Our roof is unusual with compound angles and two long valleys. We used to get leaks whenever we had heavy, wind-driven rain. Several years ago we had the roof stripped and covered 100% with bituthene (Grace Ice & Water Shield) prior to re-shingling. With the roof completely protected by the bituthene under the new shingles, we haven't had a single leak.

BTW, our contractor referred to it just as BT stated!

[LIforrelaxin]

Bituthane or Ice and Water sheld is a big neccesity. Every roofing contractor I know.... recomentds going up six feet. Now I say roofing contractor, because the are general contractors that will do roofs, and then there are guys that specialize in roofs. I have now had 3 different Roofs done in the last 5 years, in different locations. Each time the work was performed buy a roofing contractor. They all incude 6 feet in there estimates. They will do the whole thing as BT did. However 6 feet is probably more then enough. And then jsut felt above that for the rest of the roof.

Now just a little more information here. The reason the Bituthane is important is that unlike felt which will tare, thus allowing moisture through, the Bituthane, as it heats up, seals around all the nail holes, and really bonds with the shingles. Thus it creates a nice solid barrier after a summer in the sun. It will also seal up any small litte tares that happend durring an ice build up. All in all it is a great roofing product.

now back to Winni-retireds bay window. These are and always have been problematic. Much like sky lights.... as others here have said, try and find a way to get through this winter... I don't have any further suggestion on then what is mentioned here....

Then come spring have all the flashing checked, and maybe re-roof the bay window. I assume the Bay window has its own little roof. Ventilation is not an option, you just have to have a good seal around the window.

[SIKSUKR]

All good advice here. 99% of the time ice and water shield installed at least 3 feet higher than the unheated portion of the roof will prevent any water from entering if dams occur. When I reroofed 7 years ago I did to 2 courses of I&WS and also in the valleys. This fixed my ice dam leaking problem without addressing the insulation. The quick fix during the winter I had the problem was to install heat cable, even if it's not put up perfect. As soon as the cable melted down to the roof the flood gates opened and the water stopped backing in.

[sky_nh]

Lots of practical experience in these excellent suggestions. If you need a short-term solution until you get things fixed, you might do what I did.

Two winters ago I had an ice-damming problem. I wasn't able to resolve the problem right away so last winter I used the roof rake after every storm, clearing back about 10 feet from the edge of my roof. I only had to do the front roof facing west towards the sun (the back of the house is a dormer and there were no problems there). Using the roof rake took me about 15-20 minutes at most and there were no more leaking problems.

As I said, that was a temporary solution. It might work for you.

Good luck!

-- Sky

[Winni-Retired]

Off to home depot this afternoon to get a roof snow shovel and roof heater cable .. will drag off the snow then lay the cable on the roof, gutter and wrap around downspot. Mission will be to get the gutter water flowing and correct the problem in a more controlled enviroment in the spring.

I greatly appreciate the information and guidance that was offered, as we try to keep the water outside and the window dry on the inside.

Thank you all

[Lakesrider]

LOL...I'm just lucky I guess, that my North side roof is the low roof. I have a Salt Box/Cape style home. If the back was the North Side I'd have to get up on a tall ladder to clear the roof.....Yikes...I'd just move to Airizona if I had to keep doing that!

[SIKSUKR]

Though not something I would do on a longtime basis, you could also put a couple lines of rocksalt from above the ice to the roof edge to melt a pathway for the water. It worked for me.

[Grady223]

As a temporary solution, removing the gutters (aluminum I would assume) will help to allow the water to drain off easily. Then replacing the gutters with those not at the fascia but suspended below the eaves helps.

[NHBoat70]

If you are having problems this winter, purchase a roof rake to get the snow off the roof. You don't have to go all the way up, just try about half way or so. In the spring time, you should redo your roof and have the Grace Water and Ice Shield underlayment installed directly on the roof deck. My father used to break his back trying to rake it off and then when the dams did form, he basically ruined the roof by hitting it with a hammer.

Two websites: The first one is your solution and the other one is a local newspaper article about ice dams and some solutions.

http://www.graceathome.com/pages/roofing.htm

http://www.citizen.com/apps/pbcs.dll...WS02/703059790

[jmen24]

Only a couple of things to add.

Winni, you stated that you have two gable end vents and a ridge vent, but no mention of soffit vent. If you in fact have venting in your soffits, you need to remove the two gable end vents, they are disrupting the airflow in the attic. Gable vents are an inefficient form of creating cross ventilation and I say that only because most are completely undersized to create enough air flow to satisfy demand for removal. Soffit vents and roof vents work together to allow a proper flow of hot air escaping the roof and not creating warm air pockets that melt the snow on the roof. If you do not have soffit vents then you have what you have, it would not be cost effective to have someone install them.

You also mentioned that you have six inches of insulation on the attic floor. Is this blown in (loose, wool looking) or fiberglass batt. And are you sure there is only one layer.
The reason I ask is loose insulation and fiberglass batt at a thickness of 6" is only R-19 of insulating value. NH PUC Code on current residential construction is R-38, that is 12" of standard fiberglass or loose fill and just under 7" of high density foam.
If it was my house and this was an issue that I had, I would have foam insulation installed in the rafter bays and eliminate the insulation on the attic floor. The foam gives far supperior insulating values and does not require ventilation between the insulation and the roof. You will also get at a minimum of a 10 year warranty on this product and it will never change in R-value as loose and fiberglass will.

As far as installing Bitumen on your roof, one it sounds like you only have an issue with the bay window, so deal with that unless the roof is in terrible shape on the rest of the house.

Installing Bitumen on the entire sub-surface of a roof is commonly known in the trade as protecting against a poor installation. Most roofing manufacturers will not honor their warranties on the shingles if they have been installed over nothing but Bitumen. They main reason is that the Ice and Water shield heats up more than Tri-flex 30 or felt paper (not much felt being used these days but you still see it from time to time), this causes the shingles to breakdown prematurely. Industry standard for installation of Bitumen is 6 feet off the eaves and 3 feet out of the valleys, it will also typically be installed in areas of complex roof line meetings or up cheek walls on dormers (with standard step flashing above to protect the membrane.

(I am not trying to say anyone else did a bad thing by having Ice and Water installed over the entire roof, but these are a few things that you may not have been made aware of at the time.)

As far as shoveling off a roof to clear an ice dam, there is one important thing to know when it comes to ice dams. Ice dams form when melted snow or ice runs down the roof and comes in contact with freezing cold air. If you rake off the bottom 4 feet of snow, the ice dam will move up the roof 4 feet. If you are going to clear the snow off your roof, do the whole thing, it will be easier in the long run (having to do it all winter) as the ice pockets will be slim to none. If you are not interested in climbing on the roof to do this than ask and family member or neighbor that is. Good hot soup throughout the winter is allows a fine payment in my book as long as things are held in this capacity, don't try to pay a contractor with a bowl of soup if you have to hire someone.

The possible main cause for the issue with your bay window is a lack of insulation within the bay roof itself (unless the bay roof is an extention of the main roof above), contact an experienced finish carpenter as this can be remedied from the inside, but make sure they are aware of what you are looking for and know how to properly insulate the space, there is no ventilation in a bay window roof, so you will want them to install a 2 in foam board layer directly touching the roof sheathing, then LOOSELY pack fiberglass insulation into the remaining cavity. If fiberglass insulation is crushed below the thickness stated for the R-value then it will loose its insulating quality. Just like wearing layers of clothing, you will be warmer by wearing loose fitting layers than wearing 6 shirts under a jacket.

Make sure that the leak issue is resolved first, it is always easier to determine the source of a roof leak from below the roof than above. Roof repairs can be perfomed in the winter so this is an issue that can be resolved before spring.


Good luck with resolving your issue.

[no-engine]

Just to add a statement to posts. You must have efficient soffit vents, with free flow of air. The insulation should never contact under side of roof.
The "attic" space should be as close to the outside temps as possible.
With combination of insulation and ventilation, that will happen.

If it becomes necessary to replace roof shingles, I found that metal roofing was my solution! I researched, and selected a contractor who does only roofing; there are no nails or grommets visible; no fasteners are exposed. The exact term evades me: installation starts on one end and the pieces cut & crimped on site are layed together like clapboards starting at bottom. The strips are about 20" wide, starting at eaves and up to ridge or a valley.

I was fortunate that my roof had only one layer of shingles, so the new roofing went down on top, and I was not liable for removal & disposal of old materials! There is bad info out there. It did cost me more that re-roofing shingles, but not twice. One really needs to do homework for their particular situation. I have a few areas of very low pitch, and I used to shovel it off; NOW I never ever plan to go up and shovel roof! Because I selected a color which absorbs the least heat, in the summer, the spaces to not heat up as much as before.

I vote for my own safety, and after having two major leaks, I have no leaks.