Mass Timber Technical Reference Guide

What is Mass Timber?

Overview of mass timber products and their applications, where to source mass timber for U.S. projects, and key resources for developers, building designers, and construction professionals

CLT Layups and Basis of Design for Gravity Load Applications

Using layups defined in the ANSI/APA PRG 320 Standard for Performance-Rated Cross-Laminated Timber (CLT) as the basis for design

Mass Timber Cost and Design Optimization Checklists

Use these checklists as a guide as you design, estimate, and make cost-related decisions on mass timber projects.

Key Design Considerations for Mass Timber Projects

Important considerations related to construction type, fire ratings, panel thickness, member size and occupancy.

Tall Wood Buildings in the 2021 IBC – Up to 18 Stories of Mass Timber

Looking for information on the tall wood provisions in the 2021 International Building Code? This paper summarizes the provisions as well as the background and research that supported their adoption.

Tall Mass Timber Trends and Exposed Timber Allowances

Recent code changes and jurisdictional approvals provide for greater areas of exposed mass timber.

Using Wood in Types I and II Construction

Wood framing is permitted in some aspects of all five types of construction. Types I and II construction allow fire retardant-treated wood, heavy timber, and untreated wood in certain applications.

How to Create a Vertical Addition with Mass Timber

Examines the use of mass timber in U.S. projects, including code compliance, construction type, fire-resistance ratings, structural reinforcement and constructability

Heights and Areas Calculator

Use this handy calculator to determine maximum heights and areas for buildings of various occupancies and fire protection based on 2006 to 2021 editions of the IBC.

Integrating MEPF in Mass Timber Buildings: Techniques for Incorporating Building Infrastructure Systems in Exposed Wood Structures

Explores common approaches to MEPF in U.S. projects

Concealed Spaces in Mass Timber and Heavy Timber Structures

Learn which construction types allow exposed mass timber structural elements in low-rise, mid-rise and tall wood buildings.

Shaft Wall Solutions for Light-Frame and Mass Timber Buildings

An overview of design considerations, detailing options and code requirements

Design Considerations for Poured Toppings on Mass Timber Floor Panels

Explores key topics such as thickness, reinforcement, and concrete mix design, moisture and structural impacts, acoustic performance, service integration, and fire resistance

Hybrid Design: Mass Timber Floor and Roof Panels Over Light-Frame Wood Walls

Explores construction type and fire-resistance ratings, lateral system options, and acoustic performance

Exterior Walls in Mass Timber Buildings – Part 1: Code Requirements and Commonly Used Materials

Introduces the construction types that allow extensive use of mass timber, as well as material allowances, fire-resistance rating requirements (FRRs), and common exterior wall materials used in mass timber buildings

Exterior Walls in Mass Timber Buildings – Part 2: Common Floor-to-Wall Details

Reviews common detailing options for mass timber floor-to-exterior wall intersections

Exterior Walls in Mass Timber Buildings – Part 3: Cladding Material Allowances, Types, and Support Details

Detailing considerations for brick, brick veneer, and curtain wall assemblies, including structural supports and connections to mass timber panels

Exterior Walls in Mass Timber Buildings – Part 4: Panelization

Highlights benefits of panelizing exterior walls, such as faster construction, enhanced moisture protection, and improved safety

Exterior Walls in Mass Timber Buildings – Part 5: Thermal Enclosure Design

Strategies to optimize the thermal performance potential of mass timber enclosures

Specifying Appearance for CLT, NLT and Glulam

Information for designers seeking to specify appearance for cross-laminated timber (CLT), nail-laminated timber (NLT), or glue-laminated timber (glulam)

Architectural Finishes and Mass Timber: A Primer

Covers coatings and how to choose them, protective treatments vs. finishes, best practices for protecting wood in situ, and maintenance cycles

Creating Efficient Structural Grids in Mass Timber Buildings

Although a mass timber solution may work economically on grids created for other materials, a few modifications can increase efficiencies related to member sizing and manufacturer capabilities.

Delegated Design vs. Design Assist for Mass Timber Structures

Examines these common collaboration strategies, and how each adds value to the design process

Structural Design of Mass Timber Elements: Gravity Design Examples

Step-by-step guide to the design of common gravity framing systems using CLT, NLT, DLT, and glulam/GLT

Design Considerations for Horizontal Penetrations in Glulam Beams

Guidance for designing and detailing MEPF penetrations in structural glulam beams including sizing and placement of holes as well as their aesthetic integration and fire protection

Beam, Column, and Beam-Column Stability Considerations

Explores bracing parameters for compression and bending members in mass timber and light-frame wood structures

Holes and Penetrations in Mass Timber Floor and Roof Panels

Guidance for the design of mass timber floor and roof panels with openings, including structural, fire resistance, and acoustic impacts, and tips for reinforcement.

Design for Two-Way Spanning Cross-Laminated Timber

Considerations for building designers seeking to utilize CLT’s two-way span capabilities in point-supported floor systems and double-cantilever overhangs to eliminate beams and achieve thin structure depth

WoodWorks Index of Mass Timber Connections

Use this index to identify the most appropriate structural and architectural connections for your mass timber project.

CLT on Cold-Formed Steel Stud Bearing Walls: Engineering Tips for Hybrid Construction

Considerations for mass timber floor and roof panels on cold-formed steel (CFS) stud bearing walls

Differential Material Movement in Tall Mass Timber Structures

Covers reasons for vertical movement, methods of calculating anticipated movement, calculated vs. on-site verified movement, detailing options, and strategies implemented on North American projects

U.S. Mass Timber Floor Vibration Design Guide

This comprehensive guide synthesizes current design procedures and recommendations for mass timber floors and presents the results in a format that is both approachable and useful to the engineering design community.

CLT Shear Wall Options in the U.S.

Covers cross-laminated timber (CLT) and light-frame wood shear wall systems available for use now and in development

CLT Diaphragm Design Guide

Developed collaboratively with experts in mass timber structural engineering, this groundbreaking publication provides guidance for the design of CLT diaphragms used as part of wind and seismic lateral force-resisting systems.

An Approach to CLT Diaphragm Modeling for Seismic Design with Application to a U.S. High-Rise Project

This paper applies knowledge of cross-laminated timber (CLT) diaphragm behavior to practical engineering design to meet the requirements of high-seismic design in the U.S.

Construction Quality Assurance on Mass Timber Projects: Inspection and Observation

Considerations for project teams developing inspection and observation plans

Fire Design of Mass Timber Members: Code Applications, Construction Types and Fire Ratings

This paper focuses on how to meet fire-resistance requirements in mass timber projects, including calculation and testing-based methods. Companion piece to the Mass Timber Fire & Acoustic Database

Fire Design of Mass Timber Structural Members: Demonstrating Fire-Resistance Ratings of Mass Timber Products

Presents code-compliant testing and analytical methods for demonstrating the FRR of assemblies and structural members

Fire Design of Gypsum Wall Board Over Mass Timber

Fire-resistance ratings of mass timber members achieved by a combination of direct-applied gypsum wallboard and inherent timber char

Sealants and Adhesives at Intersecting Mass Timber Members

Code compliance, design impacts, and types of member and assembly intersections in mass timber buildings

Mass Timber Fire & Acoustic Database

Find fire and acoustically-rated assemblies, connections, and penetrations using this evolving database of systems compliant with North American standards.

Acoustics and Mass Timber: Room-to-Room Noise Control

This paper covers key aspects of mass timber acoustical design, including rules of thumb for optimal design, common assemblies, detailing strategies, and flanking paths. Companion to the Inventory of the Mass Timber Fire & Acoustic Database.

Designing Mass Timber Floor Assemblies for Acoustics

With careful design and detailing, mass timber buildings can meet the acoustic performance expectations of most building types.

Mass Timber Fire & Acoustic Database

Find fire and acoustically-rated assemblies, connections, and penetrations using this evolving database of systems compliant with North American standards.

Control Layer Continuity for Mass Timber Building Enclosure Design

Introductory level design guidance and effective practices for durable mass timber building enclosures

Design of Mass Timber Exposed to Weather and Wetting Cycles

Pressure treatment and other options for CLT, NLT and glulam

Mass Timber Moisture Management for Construction

Strategies for managing the unique moisture risks of mass timber building projects and developing a moisture management plan to implement during construction

Developer & Owner Resources

Mass Timber Construction Management

Mass Timber Building Insurance

Sustainability

Tall Mass Timber

Protective Design

Example Specifications for Mass Timber Panels

The example specification includes guidance on the variations and links to resources to assist in the design and specification process.

Product Manufacturers & Suppliers

Connect with these companies to source materials, products and services for your next project.

National Design Specification for Wood Construction (NDS)

American Wood Council

Special Design Provisions for Wind and Seismic (SDPWS)

American Wood Council

Fire Design Specification for Wood Construction (FDS)

American Wood Council

ANSI/APA PRG 320-2025: Standard for Performance-Rated Cross-Laminated Timber

American National Standards Institute, APA – The Engineered Wood Association

ANSI A190.1-2022 Product Standard for Structural Glued Laminated Timber

American National Standards Institute, APA – The Engineered Wood Association