Tran­si­tional area wasn’t planned prop­erly

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

QUES­TION: I have a ques­tion in re­la­tion to our new log home construction in Grand Beach. The crawl space is a four­foot height, sur­rounded by pres­sure-treated ply­wood. The edge of the un­treated ply­wood floor sheath­ing is ex­posed above the treated crawl space ply­wood at the ex­te­rior. Our plumber rec­om­mended cov­er­ing the com­plete out­side of the crawl space walls, in­clud­ing the ply­wood edge, with tar pa­per.

Do you agree with this rec­om­men­da­tion? Do we need to cover this wall or can we just put caulk­ing on the ex­posed ply­wood edge? In a few years we plan to cover this wall with stone. Thank you for your help. Irene Bois­son­neault

AN­SWER: While I had a small-town plumber give me good ad­vice on how to in­su­late a crawl space on a cot­tage many years ago, they aren’t us­ally re­garded as the best source for build­ing en­ve­lope rec­om­men­da­tions. I’ll com­ment on the “tar pa­per” sug­ges­tion and will of­fer my own take on your dilemma.

The ex­te­rior of the en­tire build­ing on mod­ern homes is of­ten re­ferred to as the “buildin­gen­ve­lope.”Thi­sis­no­tanac­cu­rate phys­i­cal de­scrip­tion, but il­lus­trates the mod­ern ap­proach to in­su­la­tion and air-seal­ing tech­niques, com­bined with mois­ture pro­tec­tion for the ex­te­rior. This may also in­clude the treated-ply­wood sheath­ing on the skirt­ing sur­round­ing your crawl space, if the walls be­hind are in­su­lated. Even if they are not in­su­lated, care must be taken to prop­erly pro­tect the fram­ing be­hind the ply­wood and the tran­si­tion be­tween the house floor and the crawlspace from mois­ture dam­age. While it may be part of the fi­nal in­te­grated so­lu­tion for pro­tect­ing this area from mois­ture dam­age, build­ing pa­per alone will not be suf­fi­cient.

The main prob­lem with your sit­u­a­tion, based on the pic­ture you in­cluded with your ques­tion, is that this tran­si­tional area was not planned prop­erly prior to com­ple­tion.

In a nor­mal sit­u­a­tion, the edge of the in­te­rior floor sheath­ing will not be ex­posed at the ex­te­rior but will be cov­ered with the ex­te­rior wall sheath­ing. This wall sheath­ing nor­mally ex­tends over this area by sev­eral cen­time­tres to al­low a proper over­lap­ping of the ex­te­rior com­po­nents of the wall. This should in­clude the sheath­ing fol­lowed by build­ing pa­per or Tyvec and then the sid­ing. In that sit­u­a­tion, in­stal­la­tion of build­ing pa­per or syn­thetic sheath­ing will help pro­tect the tran­si­tion area, but must also be cov­ered with proper sid­ing.

The dif­fi­culty in your home is that it’s con­structed us­ing older tech­niques com­bined with some mod­ern build­ing com­po­nents. Be­cause the walls of your home are con­structed with logs, there is no ex­te­rior sheath­ing and the logs act as the fin­ished sid­ing. In that sit­u­a­tion, there is no need for build­ing pa­per. This wall sys­tem is de­signed to shed rain­wa­ter nat­u­rally, which should drain off the bot­tom log, pre­vent­ing it from en­ter­ing the floor sys­tem.

Be­cause the edge of your sub­floor ply­wood is ex­posed, wa­ter run­ning down the log walls may wick back to­ward this area and ab­sorb into the edge of the ply­wood. Over time, this will cause the ply­wood to swell and rot. At­tach­ing build­ing pa­per to the sur­face of this sheath­ing will not stop rain­wa­ter from get­ting be­hind and caus­ing this dam­age. Un­for­tu­nately, nor­mal caulk- ing will also not be suf­fi­cient to seal this ex­posed edge, and wa­ter dam­age is still a strong pos­si­bil­ity.

The real so­lu­tion to your prob­lem is to in­stall a proper metal flash­ing be­tween the top of the floor sheath­ing and the walls above. This would have been rel­a­tively easy to in­stall im­me­di­ately af­ter the sub­floor was se­cured, but may be quite a bit more dif­fi­cult now. It may not be too late to in­stall the flash­ing now, but cut­ting or groov­ing a sec­tion of the wood walls may be re­quired. If the flash­ing is in­stalled above the floor sheath­ing and curved to de­flect wa­ter over this area and away from the crawl space walls, it should suf­fi­ciently pro­tect it from rot.

One other item that must be taken into con­sid­er­a­tion, be­fore in­stal­la­tion of the flash­ing, is the thick­ness of the pro­posed stone-wall cov­er­ing on this area. If the stone is thick enough to ex­tend be­yond the log walls, that idea should be re­con­sid­ered. If the stone is sim­ply a thin ve­neer, which will not pro­trude be­yond the bot­tom log on the ex­te­rior walls, then only the depth of the flash­ing needs to be planned. Any flash­ing in­stalled over the floor sheath­ing should ex­tend be­yond the pro­posed stone ve­neer on the crawl space walls to pre­vent wa­ter tracking be­hind this lower wall cov­er­ing.

De­pend­ing on the type of stone ve­neer used, build­ing pa­per, wire and mor­tar may also be re­quired on the treated wood wall sheath­ing prior to in­stal­la­tion. In that sit­u­a­tion, the build­ing pa­per should ex­tend up over the ex­posed ply­wood edge.

Also, any mor­tar, wire or metal lath should be in­stalled over this area, di­rectly up to the un­der­side of the newly in­stalled metal flash­ing. This will pro­tect this area prop­erly and may only re­quire in­stal­la­tion of a bead of caulk­ing above and/or be­low the flash­ing to pre­vent mois­ture in­tru­sion and dam­age to the sub­floor.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.