Exposed timber columns, beams, and ceilings would run through every office floor of a 12-storey Bellevue tower, the first American commercial office building to use a code path previously taken only by apartments and student housing. That is according to Waugh Thistleton Architects, the London practice designing the scheme with Seattle firm Mithun, which published the claim alongside the first drawings of its debut American building.
The International Code Council permits Type IV-B buildings to reach 12 storeys and 180 feet, the ceiling set when three mass timber construction types entered the 2021 edition of its building code. Bevel is drawn at 12 storeys and 55 metres, which converts to 180 feet, and the practice says the design would maximise both limits.
“Timber is ready to take its place at the forefront of American architecture,” Andrew Waugh said of Waugh Thistleton’s first built work in the United States.
“Of the 22 tall timber buildings under construction or built, only three are commercial,” Jennifer Cover said, with the WoodWorks chief executive naming Bevel the tallest mass timber office building in the country, and saying its fully exposed ceilings took a great deal of work to get approved.
WoodWorks records the 2021 edition as allowing exposed mass timber ceilings and integral beams in a Type IV-B building to 20 per cent of the floor area, and the 2024 edition as permitting 100 per cent exposure of the same elements. Washington has enforced the 2021 edition since 15 March 2024, and Waugh Thistleton has exposed every office ceiling in the tower.
Waugh Thistleton calls Bevel the tallest mass timber commercial office building in North America as designed, and Skanska says only that the tower is expected to be among the tallest in the United States. Skanska counted a 49 per cent carbon reduction compared with a conventional building in July, and the City of Bellevue has still to approve the design.
“A standard concrete approach created narrow office floor plates and limited connectivity across the rentable area,” Craig Curtis said, with the Mithun partner reporting that the timber came in at the same cost as concrete after the team evaluated both early in the project. The timber structure allowed a side core rather than a centralised one, and Curtis calls the wider floor plates that follow a stronger leasing proposition.
“The timber will be a visible part of the daily tenant experience,” Stewart Germain said, with the Skanska director of innovation and sustainability describing floors the developer has yet to lease, and CBRE is now marketing to a single occupier.
A steel core and seismic supports carry the tower above a below-grade concrete parking structure, with Holmes holding both the structural engineering and the fire and life-safety briefs. Skanska is targeting LEED v4 Platinum, Fitwel 2-Star, and Salmon-Safe ratings on a building it has planned for full electrification, with stormwater capture, native planting, and expanded sidewalks at the base.
It comes as 44 states carry tall timber provisions in their building codes, after Florida’s Building Commission voted the same three construction types down in July against the advice of its own fire and structural experts.
Skanska expects Administrative Design Review signoff from the City of Bellevue by late summer, and construction before the end of the year. Washington’s building code council has scheduled final adoption of the 2024 edition for 16 October and set 3 May 2027 as the date it takes effect.
