Get­ting to the root of ice damming

Winnipeg Free Press - Section G - - HOMES - ARI MARANTZ

QWe bought a house in May and were in­formed there had been an ice dam last win­ter, which caused some leak­ing inside the house. This cor­ner now has peel­ing paint, and when we re­paint, it soon peels again. What can we do to rem­edy this? Do we need to open the wall to make sure it is dry? Bruno Klassen An­swer: While it may be a lit­tle pre­ma­ture to be ad­dress­ing this is­sue this early in the win­ter, there is a chance any ice dams that have al­ready oc­curred could melt and leak inside dur­ing a mid-sea­son thaw. Tak­ing ac­tion now may pre­vent a re­cur­rence and al­low you to suc­cess­fully paint, once the weather warms up. Typ­i­cal ice damming, nor­mally at the eaves, is due to a com­bi­na­tion of fac­tors. The first one, which may be the most rec­og­niz­able to most home­own­ers, is the amount of snow on the roof. The snow on the roof pro­vides the raw ma­te­rial for this phe­nom­e­non. Ice dams are caused by melted snow, which runs down the roof un­der­neath the snow­pack and freezes at or near the eaves. If there is no snow on the roof, there is no like­li­hood of any ice damming. So the first thing to at­tempt in pre­vent­ing this from oc­cur­ring is to re­move any ex­cess snow from the roof. This may only be safely ac­com­plished with a plas­tic shovel on a bun­ga­low with a mod­er­ate to low pitch, but can also be at­tempted on other roofs from the ground with a proper roof rake, de­signed for this pur­pose. Re­mov­ing ex­cess snow will help min­i­mize the size of the ice dam but will not get at the root causes. Other vari­ables in the cre­ation of th­ese win­ter nui­sances are the pitch of the roof and the di­rec­tion they face. Very low sloped roofs have a much higher rate of ice damming for a cou­ple of rea­sons. The most ob­vi­ous one is that flat­ter roofs will drain more poorly and will be sub­ject to thicker snow ac­cu­mu­la­tions. The other rea­son is low-slope roofs typ­i­cally have less airspace be­tween the top of any in­su­la­tion and the un­der­side of the roof deck. This makes them warmer and more dif­fi­cult to prop­erly ven­ti­late. Very steep roofs are also more prone to ice damming, sim­ply be­cause they of­ten have long val­leys, with small eave­stroughs at the bot­tom. Th­ese troughs and down­spouts can be­come over­whelmed with melted snow. This wa­ter will then ac­cu­mu­late at the colder area at the bot­tom of the val­ley and can cause sub­stan­tial ici­cles and dams. This is the style of roof that may ben­e­fit the most from fre­quent snow re­moval. While the above fac­tors may con­trib­ute to the size of the icedamming prob­lem, they are not the main is­sue to ad­dress. The main cause of ice damming is warm air and heat es­cap­ing the liv­ing space into poorly in­su­lated and ven­ti­lated at­tics. This warm air can cause the tem­per­a­ture of the roof sheath­ing in the at­tic to rise above freez­ing, even on the cold­est days. As this heat trans­fers through the sheath­ing and roof­ing, it may be enough to melt the un­der­side of the snow ac­cu­mu­lated on the roof. This will be ex­ac­er­bated on very sunny days, where the heat from the sun will cause the snow to warm fur­ther, in­creas­ing the amount of melt­ing. Once the sun sets and the tem­per­a­ture inside and out­side the at­tic drops, this wa­ter will freeze, cre­at­ing the ice dam. This may go on day after day un­til the weather warms up con­sis­tently enough to cause the ice it­self to melt, of­ten caus­ing leak­age inside the home. Be­fore at­tempt­ing to re­pair any dam­aged paint in the cor­ner of the room where the ef­fects of the ice damming are seen, you must make an at­tempt to min­i­mize the war­mair leak­age that is caus­ing the is­sue. This may in­clude open­ing up the walls to see what dam­age has been done in the past, but the main area to ad­dress is the ceil­ing and at­tic above. Due to nor­mal air move­ment in your home, the ceil­ing is the area where most warm air will leak through the build­ing en­ve­lope. Pre­vent­ing this is a com­bi­na­tion of es­tab­lish­ing a good air/vapour bar­rier and hav­ing suf­fi­cient ther­mal pro­tec­tion and ad­e­quate ven­ti­la­tion in the at­tic space above. There are meth­ods of es­tab­lish­ing both a high in­su­la­tion level and a good air/vapour bar­rier, but ac­cess­ing the area where the prob­lem is oc­cur­ring is the key to re­me­di­a­tion. Get­ting into the at­tic space above the area where the leak­age from the ice dam is caus­ing prob­lems will help iden­tify where the de­fects lie. Hir­ing a knowl­edge­able in­su­la­tion con­trac­tor or a build­ing-en­ve­lope spe­cial­ist to in­spect the home and at­tic should be the first step. They should be able to pro­vide you with a so­lu­tion, which may in­cor­po­rate blow­ing in high­den­sity polyurethane foam in­su­la­tion, up­grad­ing with more con­ven­tional cel­lu­lose fi­bre in­su­la­tion, or other ap­proaches to min­i­mize warm air leak­age into this area. Once you have im­ple­mented their rec­om­men­da­tions, re­pairs to the dam­aged paint can take place. In some cases, it may be eas­ier to ac­cess and fix the de­fects above the ceil­ing by par­tially re­mov­ing it, which will al­low re­moval of any dam­aged or wet ma­te­ri­als that are pre­vent­ing proper ad­he­sion of your paint. Ei­ther way, you may have to par­tially re­move the wall and ceil­ing cov­er­ings in the prob­lem­atic cor­ner to as­sess the ex­tent of the dam­age be­fore go­ing fur­ther. While it may seem like the peel­ing paint is a su­per­fi­cial is­sue in the cor­ner of the room where the prob­lem is show­ing up, the real cul­prits are above and out­side this area. Im­prov­ing the air seal­ing, in­su­la­tion and ven­ti­la­tion in the at­tic should pre­vent fur­ther ice damming and leak­age, al­low­ing the wall to dry out or be prop­erly re­paired so a proper cos­metic fix can be done. Ari Marantz is the owner of Trained Eye Home In­spec­tion Ltd. and the past pres­i­dent of the Cana­dian As­so­ci­a­tion of Home & Prop­erty In­spec­tors — Man­i­toba (cahpi.mb.ca). Ques­tions can be emailed to the ad­dress be­low. Ari can be reached at 204-291-5358 or check out

his web­site at trained­eye.ca.

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