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  • 1

    Building Enclosures for

    Nail-Laminated Timber Buildings




    Disclaimer: This presentation was developed by a third party and is not

    funded by WoodWorks or the Softwood Lumber Board.

  • 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.

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    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 footprintand 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, enclosure and fabrication details, and key information from the Nail Laminated Timber Design and Construction Guide, which was authored by the speakers.

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    Workshop Learning Objectives

    1. Review conceptual, planning and detailing considerations

    associated with NLT, including MEP, acoustics, and form


    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

    moisture transfer 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.

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    The Building Enclosure & Considerations for NLT

    Energy Codes & Insulation Requirements

    NLT Roof Assemblies

    Site Moisture Management for Roofs & Floors

    NLT Floor Assemblies

    Air-Barriers and NLT Detailing


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    Building Enclosures for NLT

    Focus for NLT Guidelines for Building Enclosures is on NLT Roofs and Exposed Floors/Soffits + Construction Moisture Considerations for Roofs and Floors

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    Building Enclosure Design Fundamentals

    Primary function of the Building

    Enclosure/Faade: Separate the

    exterior & interior environments

    Protect mass timber during

    construction & in-service

    Serves functional and aesthetic &


    Controls heat, air, and moisture

    transfer along with noise and fire

    Designed to accommodate building

    movement, structural loads, initial &

    seasonal wood movement

    Key passive design element for a

    sustainable & energy efficient


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    Building Enclosure Design Fundamentals

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    NLT as Part of the Building Enclosure

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    NLT as Part of the Building Enclosure

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    NLT Construction & Floors

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    Properties of NLT & Building Enclosures

    Water Control

    Protect NLT from wetting and

    condensation: Dry = Durable

    Thermal Control/Insulation

    Wood provides some thermal

    resistance, but additional insulation

    still needed in assemblies/details

    Vapor Control

    Wood is a vapor barrier, no

    supplemental VB needed

    Consider drying by design & material

    placement in NLT assemblies

    Air Flow Control

    NLT is not an airtight material

    supplemental materials & details

    needed for air barrier system

  • 13

    Properties of NLT and Building Enclosures

  • 14

    US Energy Codes & NLT Building Enclosures

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    IECC 2015

    Roof, Insulation

    Above Deck

    Min. Eff. R-value

    IECC 2015

    Floor, Mass*

    Min. Eff. R-value

    8 35.7 18.1 (19.6)

    7 35.7 18.1 (19.6)

    6 31.2 15.6 (17.5)

    5 & 4C 31.2 13.5 (15.6)

    4 A/B 31.2 13.2 (13.5)

    3 25.6 13.2

    2 25.6 9.3 (11.5)

    1 20.8 (25.6) N/R

    Based on Maximum Effective Assembly U-value Tables (402.1.4 (2015)), Group R, Residential Building R-values if different shown in brackets (higher)*Assumed Mass definition, NLT w/ concrete topping

    Minimum Prescriptive Energy Code Targets for NLT Roofs

    and Exposed Floors in Commercial Buildings IECC 2015

    Note: Confirm state by state & municipal requirements depending on year of energy code adoption

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    Insulation Contribution of NLT Panels

    Minimum R-values for Roofs ~R-20 to R-35+

    Minimum R-values for Floors ~R-9 to R-20, except Zone 1 (N.R.)

  • 17

    Roof Assembly Design Considerations

    Conventional Roof Assembly

    Protected Membrane Roof Assembly (Inverted Roof)

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    Conventional Roof Sloped NLT Panels

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    Conventional Roof Sloped/Tapered Insulation

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    Conventional Roof Sloped Over-Framing

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    Protected Membrane/Inverted Roof

    Sloped Structure

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    Protected Membrane/Inverted Roof

    Sloped Over-Framing

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    Protected Membrane/Modified Inverted Roof

    Membrane Tapered Insulation

  • 24

    Managing Site Moisture Temporary Moisture

    Management Systems (TMMS)

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    Site Conditions Where TMMS Systems Are Beneficial

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    NLT Considerations Panel Sheathing & Joints

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    Site Moisture Management Fundamentals


    Keep NLT as dry as possible during shipping and


    Consider site tarping and other means to keep NLT

    dry during inclement weather

    Have a moisture management plan!


    Protect NLT will appropriate temporary moisture

    management system (TMMS) next section


    Keep water from ponding on NLT panels, drain or

    squeegee/vacuum standing water from panels onsite


    Promote drying with natural or mechanical means

    when NLT does get wet

    When covered with impermeable materials may

    need to remove to accelerate drying

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    Selecting Temporary Moisture Management

    Systems (TMMS) By Climate Risk

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    Temporary Moisture Management Systems

    High Protection, All Climates/All Seasons

    Field Membrane:

    Factory applied, fully-

    adhered, vapor

    impermeable waterproof

    membrane on sheathing

    Serves as temporary roof

    and later Air Barrier/Vapor


    Joint Treatment:

    Fully adhered/torched or

    welded field membrane

    laps immediately onsite

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    Temporary Moisture Management Systems

    Moderate Protection, Climate Index 70/ All Seasons

    Field Membrane:

    Pre-coated moisture-

    resistant bonded water-

    repellent coating in


    Joint Treatment:

    Taped with flexible

    flashing membrane or tape

    Other Considerations:

    Proprietary coated


    May have limited exposure

    time to ponding water

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    Temporary Moisture Management Systems

    Moderate Protection, Climate Index 70/ All Seasons

    Field Membrane:

    Fully adhered ponding

    water resistant vapor-

    permeable membrane

    applied to sheathing

    Joint Treatment:

    Taped with flexible

    flashing membrane or tape

    Other Considerations:

    May have limited exposure

    time to ponding water

    May be susceptible to

    damage or adhesion

    failure during construction

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    Temporary Moisture Management Systems

    Moderate Protection, Climate Index 35/ All Seasons

    Field Membrane:

    None Exposed OSB or

    plywood sheathing

    Joint Treatment:

    Taped with flexible flashing

    membrane or tape

    Other Considerations:

    Limited exposure time to

    ponding water

    Joint treatment may be

    damaged or non-bond during


    Water sealers could improve

    water resistance of sheathing

  • 33

    Temporary Moisture Management Systems

    Low Protection, Climate Index 35/ Dry Seasons

    Field Membrane:

    None Exposed OSB or

    plywood sheathing

    Joint Treatment:

    None Exposed Sheathing




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