Low slope roof, gutters and water/ice damage

Thanks in advance for any help you can offer.

I am in northern Wisconsin. I have a low slope roof covered with a rubber membrane over my garage. I installed aluminum gutters at the back (low) end a few years ago, and now I notice there has been water/ice penetration along part of the gutter line.

I took off the gutters and fascia trim, carefully peeled back the rubber roof and cut out about a 3-foot-wide segment of high density fiberboard roof insulation. I am replacing two 7" decking boards. I nailed in two small blocks of wood to the rafter overhang so I had some solid wood to nail the new fascia boards (only two rafters had bad rot in 2-3 inches at the end).

Before I start buttoning it all back up, I am curious what might have caused the roof failure. Do you think the gutters create a ledge for snow to remain in place against the garage with the freezing/thawing allowing ice to push back under the rubber membrane and cause the water damage? Should I go without the gutters?

I will attach a picture of the two damaged rafter tails. The damage is out about a foot from the wall. The garage was probably original to the house, built in the 1950s.

Thanks so much for any help.

 

Is the garage heated, full time, part time, or never?
Before I forget, using deck boards, if they are treated wood, presents an issue with what fasteners you use. But that is not your question.

I don't have a good picture (mental picture) of how the rubber roof terminates at the fascia board where the gutters are attached.

Did you get a look at the ice build up during the cold weather.

Bud

 

Thanks Bud.
The garage is unheated space. I heat it a few times each winter with an LP heater maybe 1-2 times per month just when I want to do some vehicle/garage work.

When I mentioned roof decking...I was meaning untreated 1x8s to replace some damaged roofing boards.

The rubber roof is laid over 1/2" high density fiberboard insulation. It terminates at the eve overlaying drip edge at the gutter.

I will include a couple more pictures. Just am wondering if the gutters should be reattached when I put this thing all back together,,....thanks for your help. I really appreciate it.

 

Judging from the pictures, the damage looks to be over a long stretch of the edge supporting your concerns that it was a combination of the gutters and ice buildup. I don't recall you detailing how the rubber membrane terminated at the lower edge. Did it just stop or did it wrap down the full height of the fascia?

If you could give the bottom of your fascia a good drip edge and wrap the rubber roofing or some metal trim all the way down and around that drip edge such that there would be no way water could get to the fascia or roof decking. Then the only concern would be where you penetrate the fascia to attach the gutters. Then the always necessary, when possible, step of removing the snow before the ice builds up.

We get our share of ice dams here in Maine and they are a pain.

Bud

 

Thanks again Bud.

Yes...the rubber membrane terminated at the edge of the roof, glued down on an aluminum drip edge with about a 1.5-inch overhang. An aluminum fascia slid up under the drip edge and was nailed in place under the eve.

Here is a picture of the drip edge and (at the lower part of picture) the aluminum fascia pulled back to show the damaged wood.

I have this set-up around the rest of the house without any problem...The only place I had the water infiltration was on the garage with the low-slope roof.

Before I put the gutters back up on the garage, I just wanted to make sure I was not just setting it up for the same problem again... Maybe it was just an issue with the rubber roof cement failing that allowed water to get underneath...

 

That's a standard way to terminate the shingled roof, however, it was the cause of the leak. Draw a cross section and the ice accumulation in the gutter pooled the water to where it backed up under the drip edge and got to the edge of the roof. Ice dams on homes can pool and back up a foot or more in height when really bad. between the low slope and the ice dam you don't have a lot of margin.

Just my thoughts from half a continent away. But I do believe if you put it back together as it was it will fail in the same way.

Best,
Bud

 

Thanks...I might just leave the gutters off after I replace the fascia boards. I have not been able to find any drip edge taller than 2". Trying to wrap the rubber roof around to under the soffit would mean adding more membrane, wouldn't it?

I really appreciated your advice. Of course, I took the roof apart on a 70 degree day two weeks ago, not thinking we can still have highs in the 30s and snow this time of year! YIKES!!!

 

We are melting off the latest 3" of snow we got last night, but the weather is prediction a little rain and in the 60's. I thing the trees will explode trying to bud out overnight at 60 degrees.

Tears ago I say a removable gutter where it snapped into some brackets and could be snapped out for winter to avoid the ice issues.

I am finally getting my insulation and air sealing improved to where I have minimal risk for ice dams, but when the house was first built it was a disaster. I countered that by building a makeshift 2x4 ladder up to the low slope section of my cape where I could just push the snow off with a scoop. It would take about 15 minutes to clear that slope. That is a 3/12 but I still used grippers on my shoes and a safety rope.

Being a former contractor I still have my trim bender so I would bend the piece of trim on the front of the fascia to go up on top of the roof and not jut under the drip edge. You can rent a bender or find a friendly roofer with one to make some pieces for you.

Bud

 

Gotta love houses, huh?
I used the break they have at the local lumber store a few years ago to bend fascia trim for a shed I built....If I understand you right..this picture is what you mean by bending the trim so it goes under the roof membrane....How far back under the rubber roof....5-6"? Then nail it down and then glue down the membrane?

 

That's what I was saying. The only note would be to drop the bottom below the soffit or put a down angle on it so water doesn't flow horizontally to the soffit and soak inbetween that bottom lip and the bottom of the fascia.

I dug out a picture, but basically the fascia board usually drops below the soffit to act as a drip edge. It does complicate the bending, but any innovative method that keeps the water from creeping back to the soffit.
Drip Edge Fascia Trim - Structall

Bud

 

Hi Bud.
i have sure learned a lot about rubber roofing and all the assorted products the last few weeks.
I had to do some special ordering for the underlayment and am now getting ready to button it back up, but was wondering...

I was going to lay down ice water barrier roofing underlayment along the eve.

Then the 1/2" high density insulation board.

Then the drip edge overlapped with A Roofkit 5" cover strip.....then glue the membrane back down.

I was just wondering about Roofkit 12" tape flashing...would it be useful to lay this down first with 6" covering the rooftop and the other 6" hanging down over the fascia? It seems this might create that rubber roof overhang that will prevent ice dams from backing up...Can this tapeflashing be used as the base layer taped right onto the wood, or is it for flashing over the membrane?

I hope this makes sense...
Thanks in advance.

 

I'm not that familiar with that material to say yes or no. Maybe one of the contractors will comment.

You mention an insulation board, is the garage heated occasionally and do you park snow covered cars inside. My concern is any water or snow melt must go somewhere and if not vented out, it ends up condensing on the underside of a cold roof or inside of cold walls.

Are your walls insulated and does the garage have to deal with a lot of moisture?

Bud

 

Yes...the garage might get heated up 1-2 times each month in the winter.
Yes. The cars are snowcovered.

The roof underlayment is 1/2 inch pressed board insulation....probably not more than R3 0r R4.
The exterior garage walls are not insulated. The attached house is probably insulated, but I never really looked.

 

If the snow melt doesn't drain immediately, but has to evaporate, then that humidity heads to the nearest cold surface. One of those cold surfaces could be the bottom of your roof that is covered with snow. Biting my tongue here, but could this be part or all of the moisture that has been deteriorating your roof instead of the ice dams. I'm not there to see what you see so can only ask the dumb questions.

But regardless, the snow melt needs to be considered as I have seen many garage walls, especially those with Kraft faced insulation but no drywall, where there is a layer of ice on the interior of the wall.

As for the "Roofkit 12" I did some searching and from what I saw it is just a 12" wide piece of rubber roofing and should stick well for what you propose.

Bud

 

Thanks Bud...I really appreciated your advice...I should have it buttoned up today or tomorrow.

Gotta love how they built things a half-century-plus ago

 

Careful, I was working construction a half century ago. The definition of old changes with time, now I'm just experienced .

Be sure to show us pictures when you are done.

Bud