Ice Dams


  #1  
Old 01-21-07, 12:04 PM
M
Member
Thread Starter
Join Date: Jan 2007
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
Question Ice Dams

Have a 7 year old shingle roof. Had a major ice dam this year which resulted in interior water damage. We added more insulation into attic. We are looking into a new roof. In an attempt to avoid ice dams - is a metal roof the best choice? The current roof is constructed plywood sheeting - we were informed that the screws do not bite into the roof adequetly, hence we should add strapping to ensure properly secure the metal.

Question: is a tin roof superior at avoiding ice dams?
Question: is there a huge risk in not adding strapping?

Any suggestions greatly appreciated.
 
  #2  
Old 01-21-07, 12:47 PM
T
Member
Join Date: Aug 2000
Location: USA
Posts: 15,047
Upvotes: 0
Received 2 Upvotes on 2 Posts
Metal roof is more likely to contribute to ice dams. You do not see many metal roofs in New England where winters are very cold!

In addition to having enough insulation in the attic, it is important to have enough ventilation. Sealing all gaps around perimeter of attic and around pipes, vents, etc. is important from keeping warm, moist air from entering attic. The idea is to keep the heat down below where it is needed.

Here is an article that will help you understand ice dams:

http://www.extension.umn.edu/distribution/housingandclothing/DK1068.html
 
  #3  
Old 01-21-07, 03:22 PM
Join Date: Mar 2005
Location: USA
Posts: 5,651
Received 1 Upvote on 1 Post
Ice Dams

It is not the choice of roofing materials that create ice dams. It is poor insulation and ventilation. In some rare cases, a roof/valley/exposure combination will create ice dams that can only be cured with slip sheets ot heat tape. Since yours is the first in seven years, it does not sound like fall into that category. - Were you talking to an impartial person or someone that sells and installs roofs/.

I have seen many metal roofs perform very well in northern states-MN, MI, WI, Akaska and in Ontario.

Frequently, sheets of metal are applied over shingled roofs that have problems. This allows the dam to slide off - a 'band-aid' approach, but has been used.

Before you just jump to a different roofing material, make sure you have insulation in the RIGHT PLACES and enough soffit and roof VENTS.
 
  #4  
Old 01-21-07, 04:40 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 17,505
Upvotes: 0
Received 1 Upvote on 1 Post
Wink

Many people install self-sticking rubberized sheets under roof shingles wherever ponding of water against an ice dam is possible: above the eaves, around chimneys, in valleys, around skylights and around vent stacks. The theory is that if any water leaks through the roof covering, the waterproof underlayment will provide a second line of defense. The material is sold in 3-foot x 75-foot rolls for about $80/roll. These products adhere directly to clean roof decking. Roof shingles are nailed to the deck through the membrane. The membrane is self-healing and seals nail penetrations automatically. W.R.Grace (Ice and Water Shield), Domtar (Eaveshield) and Bird all make competitive products.

Metal roofs are common in snow country so they must work! Right? Steeply pitched metal roofs in a sense thumb their nose at ice dams. They are slippery enough to shed snow before it causes an ice problem. However, metal roofs are expensive and do not substitute for adequate levels of insulation.
Like has been said its not so much in what you have on the roof . Or Like here code calls for snow stops on all metal roofs. So that can cause a ice dam But if did right the metal roof wont leak .

 
  #5  
Old 01-21-07, 05:35 PM
W
Join Date: Dec 2005
Location: USA
Posts: 2,944
Received 2 Upvotes on 2 Posts
The water and ice membrane that Ed is talking about is required by code in my area. The stuff is also great for flashing window and door openings during nrew construction.
I was born and raised and currently live in New England. When I was a kid metal and slate was the material of choice. Now they are hardly ever used, not because they are inferior materials but because they are more expensive than asphalt shingles.
 
  #6  
Old 01-21-07, 06:14 PM
T
Member
Join Date: Aug 2000
Location: USA
Posts: 15,047
Upvotes: 0
Received 2 Upvotes on 2 Posts
Thanks for clarifying why metal roofs are not used so much in New England. I recently read a survey of most used roofing materials by region of the country. Metal ranked lowest in New England.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: