Introducing the Design Guide for Nail-Laminated Timber Architectural Considerations SUBTITLE

Transcription

1 NAILED IT! Introducing the Design Guide for Nail-Laminated Timber Architectural Considerations SUBTITLE Presented by Alex Minard, Architect AIBC, MRAIC, LEED AP BD+C, CPHD Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board. MAY 2018

2 The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516. Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-aia members are available upon request. This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

3 WORKSHOP DESCRIPTION Growing interest in mass timber has led to increased use not only of cross-laminated timber, but nail-laminated timber (NLT or nail-lam) a lesser known but ostensibly more common material option. NLT is created by fastening pieces of dimension lumber, stacked on edge, into one structural element with nails or screws. It offers a unique aesthetic, flexibility of form, fast erection and a light carbon footprint and is a cost-effective option for designers looking to expose wood structure. Using lessons learned from real projects, this workshop will provide practical strategies and guidance for the safe, predictable, and economical use of NLT. Discussion will include architectural and structural considerations, envelope and fabrication details, and key information from the Nail Laminated Timber Design and Construction Guide, which was authored by the speakers. 4

4 WORKSHOP LEARNING OBJECTIVES 1. Review conceptual, planning and detailing considerations associated with NLT, including MEP, acoustics, and form variation. 2. Discuss engineering procedures for gravity and lateral design, including connection design, special loading conditions, and calculating fire resistance. 3. Study the design of NLT assemblies as building enclosure elements, while evaluating ways to mitigate heat, air and water flow into and out of the building. 4. Consider how NLT is pre-fabricated and installed, along with best practices for material procurement, tools and equipment, shipping, storage, and lifting. 5

5 AGENDA 01 / Overview 02 / Conceptual Considerations 03 / Planning 04 / Details 05 / Coordination of Services 06 / Acoustics 07 / Durability

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7 OVERVIEW Nail-laminated Timber (NLT) is dimension lumber placed on edge and mechanically fastened with nails. Part of the mass timber family of products. Can be used in vertical and horizontal applications. Lightweight, low embodied carbon, low thermal conductivity. 8

8 OVERVIEW IBC 2015 definition: Mechanically laminated decking consists of square-edged dimension lumber lamination set on edge and nailed to the adjacent pieces and to the supports. ( ) 9

9 CONCEPTUAL CONSIDERATIONS Historical Use 10

10 CONCEPTUAL CONSIDERATIONS Historical Use 11

11 CONCEPTUAL CONSIDERATIONS Form: Flat Panels Most often used horizontally but can be used vertically for walls and shafts. Typically has a layer of plywood or OSB on the top face for in-plane sheer capacity. Can be used in combination with steel, concrete, or other mass timber systems. Often left exposed as a key design feature. 12

12 CONCEPTUAL CONSIDERATIONS Form: Simple Curves Creating one-dimensional curves is relatively easy. The use of dimension lumber results in a faceted curve which becomes less noticeable as the radius increases. 13

13 CONCEPTUAL CONSIDERATIONS Form: Compound Curves 14

14 CONCEPTUAL CONSIDERATIONS Form: Compound Curves 15

15 CONCEPTUAL CONSIDERATIONS Form: Compound Curves Compound curvature NLT with tight radii in the direction parallel to laminations requires the use of short lumber segments. Noticeably faceted unless CNC milled. Labor- and material-intensive. 16

16 CONCEPTUAL CONSIDERATIONS Surface Characteristics: Texture Typical North American dimension lumber is milled with slightly rounded corners in cross section, giving NLT a distinctive grooved or ribbed texture. Planing of panels or of component laminations is possible but costly. 17

17 CONCEPTUAL CONSIDERATIONS Surface Characteristics: Texture More dramatic variation of surface texture can be accomplished through incorporating different depths of laminations. Can be done for aesthetic or acoustic reasons. Sides of lumber become visible. Impacts structural capacity. 18

18 CONCEPTUAL CONSIDERATIONS Surface Characteristics: Species Any species of wood can be used. The Guide assumes the use of species listed in the National Design Specification (NDS) for Wood Construction. 19

19 CONCEPTUAL CONSIDERATIONS Surface Characteristics: Lumber Grade and Other Desired Characteristics 20

20 CONCEPTUAL CONSIDERATIONS Surface Characteristics: Lumber Grade and Other Desired Characteristics Set expectations for NLT appearance using physical samples, reference images, and clear specifications with regionally appropriate nomenclature. These should be provided to the fabricator and discussed in detail to ensure that the design intent is delivered. All construction materials and systems are susceptible to damage during transportation, installation, or by other construction activities after installation. For wood, this includes staining from water, rust, and paint; mechanical damage; and burning. Restoring damaged NLT may be accomplished by sanding, refinishing, and patching. NLT can tolerate heavy sanding and refinishing due to its thickness; however, heavy sanding tends to degrade the even appearance of the ribs and grooves of NLT. Patching poses an even greater aesthetic challenge to the ribs and grooves. 21

21 PLANNING 22

22 PLANNING Building Code NLT is a combustible material and a code-compliant structural system for buildings with varying heights, areas, and occupancies that allow for Type III, Type IV, or Type V construction. For Type IB and Type II construction, NLT can be used as a heavy timber element for unoccupied roofs in accordance with IBC Table 601, footnotes b and c. 23

23 PLANNING Building Code NLT is a combustible material and a code-compliant structural system for buildings with varying heights, areas, and occupancies that allow for Type III, Type IV, or Type V construction. For Type IB and Type II construction, NLT can be used as a heavy timber element for unoccupied roofs in accordance with IBC Table 601, footnotes b and c. 24

24 PLANNING Building Code Type IV Construction: Floors ( ) Minimum 2x4 construction, covered with flooring, wood structural panel, or particle board. No concealed spaces. Roofs ( ) Minimum 2x3 construction. Interior Walls ( ) Minimum 2x4 construction. Exterior Walls ( ) Only if lumber is treated with fire retardant and minimum 2x6 construction. 25

25 PLANNING Building Code Type IIIA and VA Construction: Fire resistance ratings via IBC > > NDS Chapter 16 char calculation. Type IIIB and VB Construction: No fire-resistance calculations required for floors, roofs, or interior walls unless they are providing separation among occupancies. 26

26 PLANNING Building Code Prescriptive structural assembly ( & ) Or use a similar engineered solution. 27

27 PLANNING Structure NLT spans only in one direction (cannot be supported on columns alone). Typical spans range from up to 12 for 2x4 laminations to for 2x12. Maximum spans may be governed by vibrations rather than strength. Load transfers should be accomplished through supplementary framing. To reduce floor/ceiling assembly thickness, NLT can be mounted flush with the top of beams. NLT can also be suspended below the bottom of beams, with a raised floor system concealing the beams. Concept design rule of thumb: NLT can cantilever one quarter of its backspan length. Expansion joint widths should be considered in parallel with structural detailing requirement, fabrication tolerances, and installation tolerances. 28

28 DETAILS Exterior The architectural details for NLT carry the same considerations as for other building materials and systems. Wood construction detailing practices should be followed. Some details may resemble those used for other materials. Grooves between laminations can affect appearance and performance of construction details. 29

29 DETAILS Interior When a wall, door frame, or other linear element butts up against the underside of NLT, the gaps created by the grooves and the space between laminations must be considered for fire, acoustics, and aesthetics. 30

30 COORDINATION OF SERVICES Mechanical ducts, plumbing & fire protection pipes, and electrical conduits may be expressed on the building interior. Surface-mounted. Suspended. Penetrations through NLT must be coordinated with structural engineer. 31

31 COORDINATION OF SERVICES Services may be concealed. Above panel. Chase within panel 32

32 COORDINATION OF SERVICES 33

33 ACOUSTICS 34

34 ACOUSTICS Interior Space Acoustics Diffuse reflection of sound waves through staggered cross section layup. Introduction of sound-absorbing material further reduces echoes and improves speech intelligibility. 35

35 ACOUSTICS Inter-space Sound Control Transfer of sound between adjacent spaces takes two forms: airborne sound (such as speech or music) and impact sound (such as footfall). STC and IIC Testing Data for NLT Floors NLT assembly performance could be estimated by subtracting three from either the STC/IIC or FSTC/FIIC values of a CLT assembly. 36

36 DURABILITY Ultraviolet (UV) Light Where NLT is exposed to UV, its color will fade unless a suitable coating is applied. Coatings with higher pigment amounts typically resist UV longer than clear. A continuous film coating will likely develop cracks between laminations. A penetrating finish may not crack, but concealed faces of laminations will not receive the coating. 37

37 DURABILITY Moisture Exposed end grain at the edges of NLT is most susceptible to moisture, leading to swelling and distortion of the laminations. Moisture trapped between adjacent laminations or between laminations and sheathing, can impact the durability and lifespan of the NLT. Unplanned moisture exposure during construction can delay project and negatively impact quality of the work. 38

38 IMAGE CREDITS All images used in this presentation are from the Nail-laminated Timber U.S. Design & Construction Guide v1.0, with the following exceptions: Details (Exterior): Construction Progress Photo, Perkins+Will Acoustics: University of British Columbia Centre for Interactive Research on Sustainability. Architecture by Perkins+Will, Photograph by Martin Tessler Durability (UV): Pitt River Middle School. Architecture by Perkins+Will, Photograph by Michael Elkan Durability (Moisture): Samuel Brighouse Elementary School. Architecture by Perkins+Will, Photography by Nic Lehoux 39

39 QUESTIONS? This concludes The American Institute of Architects Continuing Education Systems Course Alex Minard 40