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High-Rise Wood Building EnclosuresBUILDINGS XIII – CLEARWATER BEACH, FLORIDA – DEC 8, 2016
GRAHAM FINCH, MASC, P.ENG, PRINCIPAL
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Drivers for Taller & Larger Wood Buildings
What is Unique for Enclosure Design?
Lessons Learned from Larger Wood Buildings
Case Studies of Tall Wood
Overview
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Why Taller Wood – Why Now?
Building codes are rapidly changing to
allow both larger and taller wood buildings
across North America
5&6 storey wood-frame (stick-built) now
allowed in many N.A. jurisdictions
Even taller & larger mass timber buildings
being constructed as alternate code
solutions (Canada and the US)
Many precedents in Europe and Oceania
Significant research, testing, and current
interest in taller wood buildings
Growing use of new wood products
including cross-laminated timber (CLT)
Wood seen as a sustainable and renewable
resource with bonus carbon storage
1900s era Tall Wood Buildings Across North America
2016 – UBC Brock Commons, Student Residence – Currently the Tallest Wood Building in the World, 18 storeys, 53m
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Mass Timber is Beyond Stick Framing
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It Borrows a Lot from Heavy Timber Framing
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And Borrows a Bit from Pre-Cast & Tilt-Up Concrete
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And Combines Pre-fabrication & Panelization
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And Utilizes Concrete & Steel Systems Too
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Some Precedents – Europe, Australia & North America
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The Future – From Concepts to Planned Projects
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What Makes Taller Wood Buildings Unique?
Greater use of engineered mass timber components
Alternate structural systems (post/beam, engineered panels, infill components)
Unique & new connections, interfaces & details
Hybrid steel-wood-concrete structures
Longer & heightened exposure of large wood components to rain and weathering during construction
Is not the same as stick built mid-rise wood-frame, but is also different from high-rise steel or concrete structures
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Mass/Heavy Timber – Engineered Materials
Taller structures require heavier timber & engineered lumber components
Cross Laminated Timber (CLT)
Glulam
Laminated Strand Lumber (LSL)
Parallel Strand Lumber (PSL)
Laminated Veneer Lumber (LVL)
Nail Laminated Lumber (NLL)
Many tall wood structures will also incorporate steel and concrete
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Lessons Learned
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What is Unique about Enclosures for Tall Wood?
The Need for Speed
Desire to install and close in a floor weather-tight in few days to protect wooden structure from weather
Preference towards offsite prefabrication – no time for multiple trades sequentially working onsite at once while structure is being erected quickly above
Be accommodating of inclement weather
Ensuring Long-Term Durability
Keep wood dry as possible during construction
Allow wood that does get wet ability to dry out
Extra care with assemblies & details
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Key Considerations for Wall Assemblies?
Wood studs/panels may or may not be used – steel-stud, pre-cast concrete, aluminum window- or curtain-wall all possible
Where wood is used – think “high-rise” durability
Exterior insulated & keep wood warm & dry
Continuous self-adhered air/water barriers
Drained & ventilated rainscreen claddings
Use of non-combustible materials
Careful use of impermeable materials
Connections & allowances for potentially larger movements
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Key Considerations for Roof Assemblies?
Biggest challenge is keeping heavier timber elements dry during construction & ensuring long-term durability
Heavy timber components can be challenging to dry out if able to get too wet during construction
Pre-protect/waterproofing horizontal wood in factory with the right membranes or immediately onsite
Consider designs which allow for redundancy and drying potential
Only consider conventional or protected membrane (inverted) roof designs over mass timber – keep wood dry
Conventional roof with tapered insulation over wood joists
Protected membrane roof over vented & tapered structure over CLT
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Protection of CLT & NLT Panels During Construction
Pre-applied torch applied roofing membranes applied to
horizontal panels in factory
Laps torched onsite immediately after installation
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Protection of Wood During Construction - Finland
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Lessons Learned: Keep Wood Dry & Use Appropriate Materials
Key Lessons: Don’t use paper faced insulation in contact w/ damp wood & drying through more than one layer of plywood can be too slow
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Lessons Learned: Care with Temporary Roof Membranes
Key Lessons: Be very careful with selection of temporary roof membranes on flat roofs – peel & stick can be a double edged sword
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Lessons Learned: Protect NLT from Wetting But Not Too Late
Key Lessons: Do not treat wood floors/roofs like a concrete slab - do not let nail-lam get wet & do not assume it will dry out fast enough on its own…
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Case Studies
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Bullitt Center, Seattle – 6 storeys, ~76’
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Bullitt Center – Exterior Enclosure
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Wood Innovation Design Centre – 6 storeys, ~97’
Michael Green Architecture (MGA)
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Wood Movement at WIDC - Measured
Overall building height ~97 ft – continuous glulam columns/CLT core walls with glulam beams/CLT floor panels
Glulam columns 6 tall floors – total ~ ½” (0.04%) longitudinal shrinkage/compression
CLT core walls 6 tall floors – total ~ ¾” (0.06%) longitudinal shrinkage/compression
5 ply CLT floor panels (6.5”) ~3/16” shrinkage in thickness (3%)
Initial wood moisture content of 14% dried down to a low of ~ 4%
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Wood Innovation and Design Centre Enclosure
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Wood Innovation and Design Centre Enclosure
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Wood Innovation and Design Centre Roof
R-40+ Conventional Roof Assembly – 2 ply SBS, 4” Stonewool, 4” Polyiso, Protection board, Tapered EPS (0-8”), Torch applied Air/Vapor Barrier(Temporary Roof), ¾” Plywood, Ventilated Space (To Indoors), CLT Roof Panel Structure (Intermittent)
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Wood Innovation and Design Centre
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UBC Brock Commons – 18 Storey, 180’
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UBC Tall Wood - Façade Design Criteria
Fast installation – 1 floor/day & water tight to
protect structure Thermally
Efficient, >R-16
effective walls
Inexpensive, <$50/sqft of
surface area for walls/windows
installed & finished
Installed without access to exterior –no sealing or
finishing
Pre-installed cladding & windows
Durable & High-
performance
Resistant to water & able to install in
rain
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The 4 Façade Contenders!
Pre-Cast Concrete Sandwich Panels
w/ Punched Windows
Steel Stud Framed Panels
w/ Punched Windows
Wood Stud or CLT framed Panels
w/ Punched Windows
Aluminum Window-wall
w/ Opaque Spandrel Panel Walls
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Design, Mock-up, Testing, Fabrication, Installation & Commissioning Process
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Tall Wood Structure – CLT Flat Plate with Glulam Columns
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Tall Wood Structure – Floor Moisture Protection
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Site Installation – Prefabricated Panels
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Key Prefabricated Panel Connections
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