Problematic Mansard roof- ice dams sending water inside house

[Jesse01867]

I have a mansard victorian in a suburb north of Boston that was originally built in the mid-1860s.
The house had been foreclosed, purchased by a contractor, *gulp* 'flipped', and then we bought in in August 2012.

With the massive amounts of snow we've gotten, we've developed nasty ice dams around our dormer windows on the north and east sides of the house. We've had dams before but for the first time, we are seeing water enter the house. On the north side, water is coming through the wall by the lower left corner of the window in the bathroom. On the east side, water is coming in at multiple site along a four-pane casement window.

Clearly, the acute solution is to try to block formation of dams at these sites with some vigorous roof-rake work as the snow falls.

When the first dam was removed, we discovered that the contractor's idea of a 'new roof' was to put down another layer of shingles on top of the existing ones. Legal, up to code, but lazy. Because of this, we also think that the rubber sheet designed to block water entry into the house is not present.

What are our options here?
Do we assume the whole roof is suspect and needs to be replaced?
Will a metal mansard roof help prevent ice dams in the future?
What about just replacing the north and east sides?
Are there good ways to prevent ice dam formation with a mansard roof?
I'm not sure exactly what the size of the roof is but the estimates I have come across are between $12-20/sq. foot, for upwards of $40K for a whole roof. How do mansards compare to that price point?

Any advice and insight would be appreciated.

 

[oldognewtrick]

to House Repair Talk!

Now...how old is the roof?

Did you agree to a nailover when the roof was replaced?

Who replaced the roof? A contractor or some guy in a pickup?

What were the warranty terms on workmanship from your installer.

Can you post some pics of the are?

How did they remove the ice dam?

 

[nealtw]

I think the roof was done just before they bought the house.

Ice dam material is great for dealing with ice dams when they happen. It might be far cheaper at looking at prevention instead.
Ice dams happen when the heat from the house melts the snow but the water can't get off the roof and re-freezes.
So the problem is not enough insulation and or not enough venting above the insulation to carry the heat away.
For me the first step would be to figure out the venting, as there likely is little or no insulation in there now. Venting would help in the short term.
The fix for the insulation would be to remove the interior plaster or drywall and add to the rafters so you can get a full 6" insulation and air flow above that.
If this has been happening off and on ever since a good furnace was installed there will be rot in the framing and this will be a good time to fix everything.
All this will be cheaper than a new roof and it would likely low the heating bill too.:2cents:

 

[Jesse01867]

to House Repair Talk!

Now...how old is the roof?

Did you agree to a nailover when the roof was replaced?

Who replaced the roof? A contractor or some guy in a pickup?

What were the warranty terms on workmanship from your installer.

Can you post some pics of the are?

How did they remove the ice dam?

Thanks for the welcome, ODNT.
I wasn't clear about the order of purchasing/repairs- we bought the house from the contractor that flipped it. He was also responsible for the roof 'replacement'. While he is a contractor, he seems to have been a bit lazy in the renovations.

The ice dams were removed by third parties yesterday (east side) and Tuesday (north side). Both companies went up to the roof and clear the sitting snow on the upper, lower-pitched roof and then removed the ice dams fairly completely.
We're getting more snow right now but maybe later I can get some pictures up.

EDIT: took some pictures. The first one (1066) is the window that gets the massive dam. The second picture (1067) is a different window on the same side of the house that (knock on wood!) doesn't have problems with dam build-up and water entry.

 

[Jesse01867]

I think the roof was done just before they bought the house.

Ice dam material is great for dealing with ice dams when they happen. It might be far cheaper at looking at prevention instead.
Ice dams happen when the heat from the house melts the snow but the water can't get off the roof and re-freezes.
So the problem is not enough insulation and or not enough venting above the insulation to carry the heat away.
For me the first step would be to figure out the venting, as there likely is little or no insulation in there now. Venting would help in the short term.
The fix for the insulation would be to remove the interior plaster or drywall and add to the rafters so you can get a full 6" insulation and air flow above that.
If this has been happening off and on ever since a good furnace was installed there will be rot in the framing and this will be a good time to fix everything.
All this will be cheaper than a new roof and it would likely low the heating bill too.:2cents:

Thanks for the thoughts, Neal.
We know that the insulation isn't great in this house. In fact, we had some blown in to the two bedrooms on the east side, notably around the dormer that had a MASSIVE dam build up.
With a mansard-style roof, and the lower portion with the high pitch, is it possible to have venting there? This portion of the roof is effectively the wall.
Our furnace is good and healthy. Late this summer we had some of the connections redone- the contractor installed the furnace incorrectly- and now the heating is much more effective and efficient.

Apart from the roof issue, I am now wondering what sort of damage may have happened from the water entering the walls.

Is it possible to get good venting and insulation with a mansard roof? Will we lose living space (will the walls be 'thicker') if we install this venting to get a layer of cold air in between the house and the roof?

How do you think your suggestion would compare price-wise to a new roof? We were quoted $6K to redo ONLY the east facing side of the house (the longest side, for what it's worth).

 

[Big Red]

Yes, neal is right-on. Anytime you have ice damns and ice hanging from gutters, the reason is that the attic is too warm. You HAVE to keep the attic cold thru adequate insulation and eliminating places where heat escapes into the attic from light fixtures, or wiring that pierces into the attic. Be sure to caulk any areas of heat escape before adding insulation. I've never dealt with this type of roof so you have to do some research on the best way of ventilating it and maybe the advice of a good contractor who has worked with this roof style. At the very least, I would think a number of roof vents would be needed on the upper roof area.

 

[oldognewtrick]

Remember, ventilation is a two part equation. You have to add intake at the lower point of the roof and exhaust at the upper point on the roof. Merely adding exhaust vents will not do anything for air circulation.

 

[nealtw]

Remember, ventilation is a two part equation. You have to add intake at the lower point of the roof and exhaust at the upper point on the roof. Merely adding exhaust vents will not do anything for air circulation.

Oldog: That looks like there would be common area at the lower sofffet, so maybe a few vents there would be enough. If the top singles of the lower roof were removered is the somesort of continues vent to put there instead.
Then for the upper I was thinking of vented drip edge for the bottom and regular vent for the top unless the ceiling goes right up to the top, then a ridge vent. What do you think.
I don't see step flashing beside the dormers.

Adding more room on the inside for more insulation would add about 3" to the walls inside. Not sure you have room in the dormers for that.

 

[Jesse01867]

Guys,

Thanks for your thoughts on this. I know it's going to be a big pain in the bank account but I want to make sure this gets fixed and fixed right.

A factor that I hadn't considered until roof/attic insulation was brought up was the complicated situation in our attic space.
1. The mansard roof is a second roof. There is, in some regions, an intact first roof, with shingles still attached.
2. The space between the first (older) and mansard (newer) roof is taken up by a lot of HVAC duct work and a large air handler (we have 2-zone heating/cooling so I presume this piece of equipment controls the heated/cooled forced air.
3. When I took a peek at the attic space yesterday, I saw that there is literally zero insulation in the rafters of the roof. From what Neal and Olddog have said it sounds like this is leading to a very warm space below all this snow (another ~2 feet today, hooray!) that is driving the formation of the ice dams.

For now, the best we can do is to try to clear the roof asap.

The images I attach show:
-The roof rafters barren of insulation
-A view straight up at the roof showing the rafters (2x8s?) with no insulation
-a pile of insulation sitting on some of the HVAC stuff
-the airhandler which is mounted to the first, older roof

So. Clearly this space needs insulation. We actually a company out to try to seal the space a while ago to try to get an energy rebate and they basically said they couldn't do it.
Can this space be insulated?
It sounds like we need a new roof and insulation. Can the insulation be added from the outside if the roof is replaced?
Assuming this all works, this should help the upper, flatter region of the roof. Will we still need to better insulate the lower, steeper portion (i.e., effectively our second floor walls)?
The get the proper air flow with lower and upper venting, it sounds like we will. Can this be added from the outside?

Thanks again, everyone.

 

[Jesse01867]

I don't see step flashing beside the dormers.

One of the roofers that came to remove the ice dams saw no flashing.

 

[nealtw]

I'am thinking you can make repairs to the roof and venting and then look at insulation. From the attic space you might be able to dig into the old roof and see what the rafters are and what insulation is there.

 

[nealtw]

Can you see ow the new roof was atched to the old roof or did the open up enough to set the new roof the same as the old.

 

[slownsteady]

3. When I took a peek at the attic space yesterday, I saw that there is literally zero insulation in the rafters of the roof. From what Neal and Olddog have said it sounds like this is leading to a very warm space below all this snow (another ~2 feet today, hooray!) that is driving the formation of the ice dams.

You don't need insulation between the rafters as long as you have insulation between the joists ( above the living space).

 

[schlich]

due to the limited space in there i think removing the ceiling in the dormers and have spray foam put in would take care of the problem yes it a hit to the wallet now but i could turn into a bigger hit later and it would give a complete air seal so hopefully no more problems

 

[nealtw]

due to the limited space in there i think removing the ceiling in the dormers and have spray foam put in would take care of the problem yes it a hit to the wallet now but i could turn into a bigger hit later and it would give a complete air seal so hopefully no more problems

Maybe, but not so fast That lower roof is so steep it should never be bothered with ice dams, I see two maybes and maybe both are at work here. If there is no flashing on the sides of the dormers, water has a free run, foam inside won't stop it from soaking the wood structure and then it will never dry out, the other is the window of the dormer should be over the roof, but I bet you have almost a flat area just outside the window.:hide:

 

[slownsteady]

I think Neal is onto something. With a pile of snow like that around the base of the windows, it's no wonder they leak. Every time it snows, that area needs to be cleaned of snowfall. Shouldn't be too hard, just open the window and push it off.

 

[Big Red]

They'd have to be powered vents

 

[Jesse01867]

Hi everyone, thanks for your thoughts and comments about my leaky roof.

To try to summarize, it sounds like there are three different problems here:
1. Lack of/inadequate venting
2. The roof itself- no flashing
3. Lack of/inadequate insulation

From what was written here, it also sounds like those problems are best tackled in that order, although a new roof or roof repairs should be coupled to proper venting.

The insulation would be the hardest job. We have had two companies out to try to work on this last spring. One company, once they saw the space with the false roof and air handler said they couldn't do anything. Another company came out and added *some* insulation above two rooms. They said it was sealed but I sort of have to question that given what's happening. I wish I could remove the old roof. The air handler is mounted to it so I'm not sure who could do this (contractor? Insulation companies?).

In the meantime, I'm trying to keep snow build ups away from the windows to prevent ice dams but the ultimate source of the water is the upper, flatter region of the roof which I can't reach with my roof rake.

 

[nealtw]

To try to summarize, it sounds like there are three different problems here:
1. Lack of/inadequate venting
2. The roof itself- no flashing
3. Lack of/inadequate insulation

From what was written here, it also sounds like those problems are best tackled in that order, although a new roof or roof repairs should be coupled to proper venting.

It would be nice to save the roof, I have suggestions for the roof and maybe Oldog can tell us if they are possible.

If the ice dams are on the upper roof , that is caused by heat coming off the top of the lower sloped wall.
I think we could figure out soffet vents for that .
1. might be just drilling say 3" holes in to the overhang of the upper roof between each rafter.
2. If there is a common area there , so air can travel along and then go up between the rafters, then maybe a few bigger holes with screen.
3 If 1 and 2 don't seem possible or just ugly there are vented drip edge but that goes under the first row of shingles.

A few box vent across the back of the house near the peak.

Looking at the rafters in the new upper roof, are they 2x6 or 2x8?

I think some of these options can be done without distroying the upper roof.

We will have investicate the window dormers, I think there could be flashing there with more shingle added just for looks, if not there could be bigger problems there, but I think a good roofer could fix that up with out a full re and re.

 

[oldognewtrick]

It looks from the photos that there is a bit of a overhang at the pitch change. May be as simple as adding starter vent along that edge and ridge vent on the peak. IF the is ice and water shield on the upper low slope..