De­signs kept rain out of condo projects

Storm wa­ter sys­tem passed test

Calgary Herald - Calgary Herald New Condos - - New Condos - CLAIRE YOUNG

There’s over­land flood­ing, such as that re­cently ex­pe­ri­enced by great swaths of Calgary when rivers over­ran their banks.

And then there’s the kind of dam­age that hap­pens when base­ments or park­ing garages get wet be­cause nearby sur­face wa­ter from rain has seeped through the ground into foun­da­tions.

With the kind of rain Calgary saw lead­ing up to the great flood in June — 78.6 mil­lime­tres in two days — some home­own­ers were wor­ried this wa­ter would en­ter their base­ments.

But two multi-fam­ily builders in Calgary had projects with de­sign ele­ments that helped keep struc­tures dry from the heavy rains.

Avi Ur­ban re­ceived a Calgary Award in June for en­vi­ron­men­tal achieve­ment. The hon­our was given for the com­pany’s in­no­va­tive storm wa­ter sys­tem at its Vic­to­ria Cross town­home de­vel­op­ment in Cur­rie Bar­racks in the city’s south­west.

The storm wa­ter sys­tem col­lects rain­wa­ter and di­verts it into chan­nels be­tween build­ings.

The wa­ter then col­lects in an un­der­ground cis­tern, where it is fil­tered through var­i­ous lay­ers of ma­te­rial and fi­nally ab­sorbed into the earth with­out feed­ing into the city’s storm wa­ter sys­tem.

Cather­ine Lough­lean is the chair­woman of the condo board for part of the Vic­to­ria Cross de­vel­op­ment, where she lives with her hus­band and five chil­dren.

“We have had no flood­ing,” says Lough­lean.

“We have three build­ings in our condo. Each build­ing has a sump pump and the wa­ter is pumped away from our build­ings to­ward the cen­tre of our back­yards, which is then car­ried off into our own drainage sys­tem. None of it ac­tu­ally goes back into the city wa­ter sys­tem.”

She was cu­ri­ous to see how it would fare through the heavy rains.

“This has been a fan­tas­tic test to see how this has worked,” says Lough­lean.

Mike Bucci of Van­cou­ver­based Bucci De­vel­op­ment Ltd. says his build­ings in Calgary — in­clud­ing Tribeca in Mis­sion, Xenex on 12th Av­enue and Next in Bridge­land — all came through the heavy rains dry.

Two de­sign con­sid­er­a­tions con­trib­ute to keep­ing it that way: keep­ing wa­ter out of a park­ing struc­ture, and us­ing rain­screen tech­nol­ogy to help the build­ing dry out prop­erly.

“We go to great lengths to make sure we have a dry parkade,” says Bucci, who is vice-pres­i­dent of de­vel­op­ment.

“All of our build­ings are de­signed to ac­com­mo­date a lot of sub-sur­face wa­ter move­ment. I know a lot of de­vel­op­ers have the view that it’s OK for the walls to be damp from time to time. We go to quite a length to make sure that never hap­pens.”

Bucci’s parkade en­trances are raised two feet (61 cen­time­tres) above side­walks, pro­vid­ing a bar­rier to keep rain­wa­ter from flow­ing into the parkade, while also cre­at­ing a sense of sep­a­ra­tion of pub­lic and pri­vate space.

“That would have helped a lot of build­ings — two feet is a lot,” says Bucci, adding that higher en­trances are not a de­fin­i­tive flood-preven­tion el­e­ment that would keep out all over­land river flood­ing such as what some parts of the city ex­pe­ri­enced.

Heavy rains can also raise the wa­ter ta­ble be­neath a build­ing, which is an­other way wa­ter can come in con­tact with foun­da­tions and cause leak­ing.

Bucci’s lat­est build­ing, Ven, is planned for Sun­ny­side, an area with a high wa­ter ta­ble, says Bucci. The site is at the bot­tom of McHugh Bluff, where wa­ter runs down when it rains.

“Rather than just re­ly­ing on the con­crete (foun­da­tion), we’re go­ing to over­size the ex­ca­va­tion for Ven and take the shoring walls — the tem­po­rary walls — and make them out of solid con­crete and drive them down deep, deep into the bedrock; way deeper than we would nor­mally do.

“Those con­crete shoring walls will form a per­ma­nent cut-off wall, which will al­low all the wa­ter com­ing off the hill­side to part around our site, rather than just re­ly­ing on the usual damp-proof and water­proof of the parkade walls. We’ll have this ex­tra layer to push the wa­ter away from the parkade.”

It will cost $800,000 to $900,000 more than a typ­i­cal parkade struc­ture due to this ex­tra pro­tec­tion, he says.

Bucci De­vel­op­ments has brought its ex­pe­ri­ence build­ing on the rainy West Coast to Al­berta, in­clud­ing rain­screen­ing on its ex­te­ri­ors to help its build­ings dry out af­ter a rain, help­ing to pre­vent mould from grow­ing.

“We come from a wet, trop­i­cal cli­mate, ba­si­cally,” says Bucci.

“We know that even in Calgary’s en­vi­ron­ment, you need a rain­screen assem­bly. Your rain, even though it doesn’t last as long, it hits so much harder.”

Rain­screen­ing pro­vides an airspace be­hind the ex­te­rior cladding. It pro­vides a sec­ond drainage plane, so that any wa­ter that gets be­hind the sid­ing — vinyl, stucco, or other — can still run down.

Se­condly, it’s a dry­ing mech­a­nism, re­ly­ing on the chim­ney­ef­fect of hot air ris­ing and draw­ing air up through the space.

“There’s air con­stantly be­ing pulled through that airspace that is dry­ing out the build­ing,” says Bucci.

“Even if you do get hit with a mon­soon rain­storm, the prob­lem with a face-seal sys­tem (with no airspace) is that the mois­ture just sits there un­til Au­gust, when it fi­nally gets baked out of the build­ing. With a rain­screen assem­bly, im­me­di­ately the air flow gets go­ing through there and dry­ing out the build­ing.”

Homes by Avi

A draw­ing of Vic­to­ria Cross by Avi Ur­ban, which won a Calgary Award for its storm wa­ter sys­tem.

Bucci De­vel­op­ments

The Ven pro­ject in Sun­ny­side is de­signed to keep out wa­ter.

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