Stucco may not be ideal for cot­tage ap­pli­ca­tion

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

QUES­TION: Our cot­tage is fin­ished with vinyl and the last two feet of pony wall is pres­sure-treated wood sit­ting on a con­crete foot­ing. We want to stucco the pony wall and I am won­der­ing if one needs to use a flash­ing, slid­ing it un­der the first row of vinyl and then over top edge of the new stucco to act as a drip edge.

Some ar­ti­cles are not clear if lath is needed and whether spac­ing should be hor­i­zon­tal or ver­ti­cal. House wrap was the first step, then lath, then metal mesh and two or three coats of stucco. Also, if a drip edge or flash­ing is not used, what can be used to make a clean line? Butting stucco right up to vinyl doesn’t sound like it will look great. I know there are lit­tle holes in the bot­tom of vinyl and won­der­ing where this wa­ter will go with­out some kind of flash­ing.

I re­ally want to know if this is an is­sue, or not? Your thoughts and guid­ance would be greatly ap­pre­ci­ated.

— Steve K. AN­SWER: There are many cot­tages built with a short knee-wall or pony wall above a foot­ing on grade sim­i­lar to yours, in­clud­ing my own. While the vinyl sid­ing pro­vides good pro­tec­tion for the wall sheath­ing, there is of­ten lit­tle pro­tec­tion for this area on the knee-wall.

For­tu­nately, you have had the fore­sight to in­stall pres­sure-treated ply­wood, which should re­quire min­i­mal pro­tec­tion from the el­e­ments un­less you are do­ing this for cos­metic rea­sons, which I un­der­stand. We will ex­plore typ­i­cal stucco ap­pli­ca­tion pro­ce­dure and dis­cuss some ad­van­tages and con­cerns with your pro­posed ap­pli­ca­tion.

I am con­fi­dent that your method of in­stal­la­tion of stucco will pro­vide ad­e­quate sup­port and pro­vide a proper fin­ished prod­uct, but one com­po­nent may not be nec­es­sary. As you have stated, the first com­po­nent should be the build­ing paper or House­wrap, but the need for ad­di­tional fur­ring strips or lath is ques­tion­able. As long as the treated ply­wood you have in­stalled is in good con­di­tion and prop­erly se­cured, that should be suf­fi­cient for sup­port of the stucco wire. The wire is de­signed to be nailed or sta­pled di­rectly to the sheath­ing and pro­vide a small drainage plane or gap be­hind the fin­ished stucco, once cured. This should be suf­fi­cient and I am un­sure what added value the lath would pro­vide.

The only ad­di­tional com­po­nent needed would be finer metal mesh at the cor­ners, which is of­ten called “di­a­mond lath” be­cause of the shape of the metal grid. I don’t think this is what you are re­fer­ring to, but its in­clu­sion would pro­vide added strength to the fin­ished prod­uct at the cor­ners where it is par­tic­u­larly vul­ner­a­ble to dam­age.

As far as in­clu­sion of a drip flash­ing above the stucco, that is a very good idea. You are cor­rect that the small holes or gaps at the bot­tom of the in­di­vid­ual sec­tions of vinyl sid­ing are de­signed to shed any wa­ter that gets through the sur­face. A flash­ing in­stalled un­der the bot­tom sec­tion of sid­ing should pre­vent wa­ter from eas­ily leak­ing be­hind the stucco, pre­vent­ing dam­age. The bot­tom of this flash­ing should also pro­vide a nice straight edge for the top of the stucco, to sat­isfy the aes­thetic con­cern you have also raised.

I would also sug­gest look­ing into in­stal­la­tion of an ad­di­tional J-mould­ing at the bot­tom of the stucco to pro­vide a sim­i­lar smooth edge and pre­vent wick­ing up mois­ture from the con­crete foot­ing. This edg­ing piece should be in­stalled sev­eral cen­time­tres above the con­crete foot­ing to pre­vent cor­ro­sion and wick­ing.

While I have con­firmed that you are tak­ing the proper steps for in­stal­la­tion of typ­i­cal stucco on the knee-wall be­low the walls of your cot­tage, I have not ad­dressed the ap­pro­pri­ate­ness of this ma­te­rial for use in this area

Stucco, like most ma­sonry prod­ucts, is some­what por­ous. It can eas­ily ab­sorb mois­ture, once cured, but also re­leases it fairly quickly if there is noth­ing pre­vent­ing dry­ing. If there is suf­fi­cient block­age to proper dry­ing, the stucco will quickly de­te­ri­o­rate. Be­cause of the prox­im­ity of the knee-wall to the con­crete foot­ing and grade, this is a strong pos­si­bil­ity. Snow, rain, and ex­ces­sive veg­e­ta­tion or shade from trees will pro­mote this de­te­ri­o­ra­tion. Depend­ing on the lo­ca­tion of your cot­tage, you likely have most or all of these con­di­tions present, as well as very high rel­a­tive hu­mid­ity much of the year.

In sim­pler terms, while proper ap­pli­ca­tion of stucco will pro­vide a good aes­thetic ap­peal for the knee-wall along the bot­tom of your cot­tage, it may not be an ideal choice. A bet­ter choice would be a few good coats of ex­te­rior stain or primer and paint. If this is not to your lik­ing, mois­ture-re­sis­tant ma­te­rial such as ce­ment-based sid­ing or a sim­i­lar prod­uct may be bet­ter, but may re­quire paint­ing as well. Be­cause you have wisely cho­sen pres­sure-treated ply­wood for the sheath­ing, cov­er­ing to pre­vent mois­ture dam­age is not nec­es­sary, which will leave you more lat­i­tude in your choice of cov­er­ing for cos­metic rea­sons only.

Cot­tager has ques­tion about vinyl-fin­ished prop­erty.

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