Stains in at­tic not al­ways cause for con­cern

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

QLast win­ter I took a look into the at­tic and no­ticed black stains and wa­ter marks on a por­tion of the sheath­ing ma­te­rial. This sum­mer I cleaned the por­tion of the black stain with a dry mop, as much as I could reach from the hatch open­ing. While the black stains are ei­ther mould or just black dust from at­tic in­su­la­tion set­tled on the wet sur­face in win­ter, I am con­cerned with the wa­ter marks. Are they from mois­ture too or from a pos­si­ble leak? I prob­a­bly had an ice dam this win­ter in that area of the roof. I would ap­pre­ci­ate your opin­ion. Thank you in ad­vance, Eu­gene. An­swer: Of­ten our homes may ap­pear quite prob­lem­atic, es­pe­cially to the un­trained eye, but in re­al­ity, what’s oc­cur­ring may not be much of a con­cern. At­tic stains may fall into this cat­e­gory, de­pend­ing on the sever­ity. Al­most all at­tics in homes more than 25 years old will have some mois­ture stains on ei­ther the sheath­ing or the fram­ing. In a rea­son­ably well-in­su­lated and vented at­tic, stains may ap­pear due to con­den­sa­tion. This hap­pens due to trapped damp air, of­ten in the late fall or early win­ter. When this hu­mid, rel­a­tively warm air can­not es­cape the at­tic space be­fore the tem­per­a­ture drops, con­den­sa­tion can oc­cur on the cold­est sur­faces in the at­tic. Those of­ten are the un­der­side of the roof. When this phe­nom­e­non oc­curs, the sheath­ing or fram­ing may be­come slightly wet on the sur­face. If the tem­per­a­ture drops be­low the freez­ing point, of­ten at night af­ter the sun goes down, this mois­ture will freeze. Look­ing up into an at­tic in the days or weeks af­ter the first few sub-zero days will of­ten re­veal a layer of white frost in some ar­eas. This frost will nor­mally melt on warmer win­ter sunny days, but may re­oc­cur at night when the sur­face tem­per­a­ture of the roof drops. Also, a heavy layer of snow on the sur­face of the roof will in­su­late the sheath­ing and may keep the frost from melt­ing, al­to­gether. If the frost does melt, it will fur­ther wet the wood in the at­tic, stain­ing it. Small stains may only be this sur­face mois­ture bleed­ing out min­er­als or dirt from the wood and are of­ten brown­ish in colour. Th­ese stains may turn darker in colour over the years, as the frost/melt cy­cle re­oc­curs. In many cases the con­tin­ued wet­ting of the sheath­ing will cause it to rot, but that may take sev­eral years or decades, de­pend­ing on the at­tic ven­ti­la­tion. The other two pos­si­bil­i­ties for the stains in the at­tic are ex­cess air in­tru­sion from the liv­ing area in the home and leak­age through the roof sur­face. If the at­tic floor is poorly in­su­lated or air sealed, warm air can cer­tainly leak in from the heated liv­ing space and cause some ma­jor mois­ture is­sues. That may be vis­i­ble through your at­tic hatch by a trained pro­fes­sional as much more than a few stains. The re­me­di­a­tion for that is­sue is more com­plex and will be left for an­other dis­cus­sion, as it has been ad­dressed many times in pre­vi­ous ar­ti­cles. Roof leak­age can of­ten be seen as dark black stains, con­cen­trated and ra­di­at­ing out from one or more in­di­vid­ual lo­ca­tions. Th­ese are com­monly seen un­derneath roof vents, plumb­ing stacks, vent hoods and around chim­neys. If th­ese iso­lated spots are seen away from th­ese roof pen­e­tra­tions, then the roof may be dam­aged and leak­ing. At­tempt­ing to clean the wood sur­faces in your at­tic is a fu­tile ef­fort. While you may have suc­ceeded in re­mov­ing some sur­face dirt or mould, that will not help ex­tend the life of this ma­te­rial if it con­tin­u­ally gets wet. If the stains are only sur­face ones, caused by pe­ri­odic frost ac­cu­mu­la­tion, there is no need to do any­thing. If your at­tic has rea­son­able ven­ti­la­tion, it should pre­vent the frost or con­den­sa­tion from re­main­ing in that space for more than a short time. As long as the wooden fram­ing and sheath­ing is al­lowed to dry af­ter a brief wet pe­riod, dam­age may not oc­cur, ex­cept af­ter many years. I com­mend you on at­tempt­ing to be proac­tive in pre­vent­ing a prob­lem within your at­tic, but your re­me­di­a­tion meth­ods are mis­guided. Rather than at­tempt­ing to me­chan­i­cally re­move some stains, which will be dif­fi­cult and use­less, fo­cus­ing on re­duc­ing the mois­ture in the at­tic area makes more sense. En­sur­ing sof­fit vents are not blocked or painted over and roof vents are un­dam­aged and cleared of snow is a much more wor­thy ef­fort. If you did have ice damming it may be a sign there is a prob­lem with th­ese is­sues, so im­prov­ing them will be more worth­while. See­ing some stains on the un­der­side of the roof sheath­ing, or fram­ing, may not be a cause for se­ri­ous con­cern. Clean­ing them off man­u­ally will not be worth the ef­fort, but fur­ther im­prove­ments to in­su­la­tion and ven­ti­la­tion may pre­vent the prob­lem from get­ting out of hand. If the stains are very dark, iso­lated, and ra­di­at­ing out, hir­ing a pro­fes­sional to re­pair or up­grade the roof may be nec­es­sary. Ari Marantz is the owner of Trained Eye Home In­spec­tion Ltd. and the past pres­i­dent of the Cana­dian As­so­ci­a­tion of

Home & Property In­spec­tors — Man­i­toba ( Ques­tions can be emailed to the ad­dress be­low. Ari can be reached at 204-291-5358 or check

out his web­site at trained­


Owens Corn­ing's At­tic Stair­way In­su­la­tor is a tent made from in­su­lat­ing ma­te­rial

and re­flec­tive foil that cov­ers the stair­way open­ing.

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