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May 23, 2016

$56M Denny Hall renovation finishing in August, six months ahead of schedule

By BENJAMIN MINNICK
Journal Construction Editor

Photos by Benjamin Minnick [enlarge]
Denny Hall is the oldest building on the main UW campus.

Up in the attic of Denny Hall on the University of Washington campus, Robbie Lund pointed overhead to a maze of wooden beams and proclaimed that no one had seen them since the 1890s.

Lund, a superintendent with BNBuilders, has been working since July 5 on a $56 million renovation of the oldest building on campus.

Lund said those attic beams were covered with 2 to 3 inches of plaster by the time the original wood, brick and stone building was finished in 1895.

Crews from BNB stripped the plaster and have been installing insulation and drywall to create a two-story loft in the fourth floor and attic for teaching assistants as part of the renovation. This time the beams are not being covered.

In the un-lofted south attic, crews replaced a “crude” air-conditioning system — which Lund said was more like a swamp cooler — that was installed in a concrete bathtub-like enclosure during the mid-1950s.

The new 26,000-pound air-handling unit had to be hoisted, piece-by-piece, into the space for assembly. That operation took about three and a half weeks.

Crews removed two massive 7-by-14-foot ducts from the old system that dropped down to the fourth floor and exited out the back of the building through giant louvers. Lund said part of the fourth floor, unusable with the ducts in, is being turned into lab space and windows are being installed in the openings where the louvers were.

This part of the attic is being turned into a loft for teaching assistants.

Lund said work in the upper floors has been tedious at times. For example, workers installed 10,000 seismic clips to connect existing wood elements (and a few new elements) to one another for added support. Each clip required up to 12 screws.

Ugly past

BNB started the renovation by gutting the 86,400-square-foot building in an effort to reverse past “improvements.”

The mid-1950s renovation had closed up an open central staircase and skylight atrium, shrunk the lobby, changed building access points and broke an auditorium with 38-foot ceilings into two floors of offices. The old renovation also failed to fortify the building or add any insulation.

For the new staircase and skylight atrium, crews cut out a center section of the building while simultaneously installing a shoring tower to support the weight of the building. Lund said it took more than four months to design the tower and a month to build it. It was tricky to design because existing and new building elements had to be taken into account.

Crews flew the stairs in through the skylight opening using a crane, and then installed the 16-by-20-foot skylight made up of 16 panes that follow the building's roof line.

Seismic support comes from 14 shear walls made of concrete and rebar that run the height of the building. Crews drilled into existing masonry and epoxied rebar into the blocks to tie the new shear walls into the building.

Lund said the old lobby was about 10 feet wide and the new one is close to 50 feet. The space is being brightened up with whitewashed wood panels on the walls and polished concrete floors.

Robbie Lund points out a shear wall that made window sills much deeper.

A long open space on the third floor is being transformed into an active learning lab with 24 video monitors.

An audio lab with recording studio is being created on the first floor. The studio is essentially a floating concrete box that sits on rubber isolators.

Lund said they couldn't restore the original auditorium because the university would have lost about 40 offices.

Ironically, the 1950s renovation may have saved the building: Lund said the UW wanted to demolish the building back then, but found it cheaper to renovate it.

Blast from the past

Exterior work has been a little less extensive.

Crews found about 30 sandstone blocks on the building's base had delaminated due to water intrusion and plants growing on them. Lund said the blocks were mined from a quarry near Wilkeson in Pierce County that had since closed, but they convinced the owner to reopen so they could get matching replacements. Undamaged blocks were sandblasted.

Water in the basement was tracked to a leaking foundation. Lund said they shotcreted around the entire stacked stone foundation, then applied waterproofing and installed a drainage system. Additional shotcrete was applied below the main entry stairs for reinforcement.

To fight future water intrusion, BNB installed a concrete box-like maintenance strip around the building to contain vegetation.

While digging out around the foundation, crews uncovered a stone block near the main steps that had 1861 chiseled in it. Lund suspects the block may have come from a building on the university's original campus in downtown Seattle.

Technology boost

Jason Limp, BNB project executive, said there are about 25 drawings of Denny Hall from the 1890s, and drawings from the 1950s renovation “were all over the place.”

To figure out what was going on with the building, BNB took laser scans of every room while soft demolition was underway.

Limp said the scans allowed them to avoid 500 to 600 potential conflicts, resulting in fewer request-for-information filings and lower costs.

The scans also revealed some brick walls that were two layers thick instead of three. BNB fixed that with shotcrete and rigid insulation.

“We've been fortunate in this building that we haven't had surprises that are game-changers,” Lund said.

The scans also reduced the amount of on-site labor needed to fix or modify the installs in the field, according to Lund. “It came out right the first time,” he said.

BNB was originally hired for the renovation in 2008, but the recession hit and the UW put the project on hold. At the time, BNB had a third party take laser scans of the attic.

Foundation work unearthed this block thought to be from the UW’s original downtown campus.

Limp said the old laser measurements took weeks to scan, download and interpret. Newer technology takes less than a day to do the same work.

The modern equipment is helping BNB finish on Aug. 1, six months ahead of schedule, according to Limp.

Lund said collaboration between the design team, BNB and its trade subcontractors also helped to compress the schedule.

BNB is working under a $34 million GC/CM contract. Portland-based Hacker, previously known as THA Architecture, is the architect.

Other team members are: Glumac, mechanical engineer; Travis, Fitzmaurice & Associates, electrical engineer; PCS Structural Solutions, structural engineer; Coughlin Porter Lundeen, civil engineer; and Site Workshop, landscape architect.

Denny Hall houses offices and classrooms for the College of Arts and Sciences, including the departments of Anthropology, Classics, Germanics and Near Eastern Languages & Civilization. It also is home to college's Language Learning Center.


 


Benjamin Minnick can be reached by email or by phone at (206) 622-8272.


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