Was bal­cony wa­ter­proof­ing OK?

Out­side ex­perts say Berke­ley tragedy in­ves­ti­ga­tion should fo­cus on the wa­ter bar­rier and drainage.

Los Angeles Times - - THE STATE - By Rong- Gong Lin I I and Lisa Girion ron.lin@latimes.com Twit­ter: @ ron­lin lisa.girion@latimes.com Twit­ter: @ lis­a­girion Times staff writ­ers Javier Pan­zar in Berke­ley and Paige St. John in Sacra­mento con­trib­uted to this re­port.

As of­fi­cials in­ves­ti­gate the sud­den col­lapse of a Berke­ley bal­cony last week that killed six and in­jured seven, out­side ex­perts say it’s ob­vi­ous what hap­pened: Wa­ter got into the bal­cony and didn’t get out, rot­ting the wood that kept it in place. The big ques­tion is why. Berke­ley city of­fi­cials gave no timeline for the re­lease of find­ings on why the bal­cony col­lapsed.

But out­side ex­perts ex­am­in­ing ar­chi­tec­tural draw­ings and pho­to­graphs of the fifth- floor bal­cony’s rem­nants say there are a num­ber of is­sues in­ves­ti­ga­tors should fo­cus on.

“We would want to look at what the wa­ter­proof­ing sys­tem is on that bal­cony,” Taryn Wil­liams, a civil and struc­tural engi­neer in San Fran­cisco who in­ves­ti­gates struc­tural and wa­ter­proof­ing fail­ures, said in an in­ter­view last week. “We also want to look at if wa­ter does get in, is there a way for it to get out?”

Another ques­tion: Did the wa­ter­proof­ing on the deck — a thick layer of sticky as­phalt topped with black plas­tic — have any gaps?

“Is it sealed? And how ef­fec­tively is it sealed? And how many lay­ers of re­dun­dancy are there within that seal?” Wil­liams said.

Her em­ployer, Simp­son Gumpertz & Heger, was later hired to in­ves­ti­gate the bal­cony’s col­lapse, and said she could not com­ment fur­ther.

The f irm de­clined to say who hired it.

Be­fore the col­lapse, there should have been warn­ing signs easily no­ticed by an in­spec­tor on a rou­tine main­te­nance sched­ule, one ex­pert said.

“Bal­conies just don’t fall off a build­ing like what we saw with­out hav­ing a few years of de­te­ri­o­ra­tion,” said Bill Leys, a for­mer deck wa­ter­proof­ing con­trac­tor who now in­spects decks in San Luis Obispo for his com­pany, Deck­Ex­pert. com.

“The com­mon man or woman walk­ing on a bal­cony might look at it and see a lit­tle crack and say, ‘ No big deal,’ and in my mind, I say, ‘ Oh, my God. How much dam­age is un­der­neath?’” Leys said.

He said he was stunned to see an im­age of the col­lapsed bal­cony’s un­der­belly.

The wooden sup­port beams were so de­cayed along one edge they had mostly van­ished.

Leys said the deck may have been built f lat, in­stead of at a slight an­gle. “It has to have slope in it to shed wa­ter,” he said.

He also said the ar­chi­tec­tural plans he re­viewed omit­ted an im­por­tant layer in the deck — a plas­tic, dim­pled “drain mem­brane” that puts a gap of air be­tween the con­crete deck sur­face and the wa­ter­proof­ing mem­brane layer cov­er­ing the sheet of ply­wood on top of the wooden sup­port beams.

With­out a gap of air roughly 1⁄ 4- to 1⁄ 2- inch thick, wa­ter that is ab­sorbed into the con­crete gets stuck next to the wa­ter­proof layer. That would pro­vide ideal con­di­tions for dry rot fun­gus to grow.

Leys said he sus­pected that the wa­ter­proof­ing mem­brane had been punc­tured, al­low­ing wa­ter to soak into the wood.

He said he has seen decks with “mas­sive prob­lems un­der­neath” be­cause wa­ter had seeped in through a small crack and gone un­re­paired for years.

“But wood is cel­lu­lose. It’s a sponge. It soaks up wa­ter,” he said. “It is go­ing to re­main trapped there for some time.”

Fi­nally, Leys said, bal­conies that have stucco sur­round­ing them should have vents to air the wood out if they get wet.

He didn’t see them in the de­sign or in photos.

Given the mas­sive wa­ter in­tru­sion present, “It prob­a­bly still would’ve dry rot­ted, but at least it would have had a bet­ter chance,” he said.

Leys said there would have been ways to rem­edy the sit­u­a­tion dur­ing con­struc­tion.

He said if he were con­fronted with a f lat deck, he would have used a dif­fer­ent tech­nique that can add slope and also pro­vides wa­ter­proof­ing.

Gene St. Onge, a civil and struc­tural engi­neer in Oak­land, said the sit­u­a­tion un­der­scores the im­por­tance of reg­u­lar in­spec­tions to iden­tify wa­ter- in­tru­sion prob­lems in roofs, bal­conies and decks be­fore they get worse.

“There had to have been a lot of stains and warp­ing to show that wa­ter is get­ting in there. If main­te­nance com­pa­nies are do­ing their job, they should be go­ing around and check­ing these things,” he said.

Mark Boster Los An­ge­les Times

CON­STRUC­TION CREWS re­move pieces of the bal­cony that col­lapsed in Berke­ley, ex­pos­ing what ap­pears to be dry rot lum­ber. The col­lapse killed six peo­ple and in­jured seven just a few blocks from UC Berke­ley.

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