ufp06a

Designing Floor Systems with Engineered Wood Joists

Course Sponsor

Designing Floor Systems

with Engineered Wood Joists

Universal Forest Products, Inc. 2801 East Beltline NE

Grand Rapids, MI 49525

616-365-6608

E-mail

[email protected]

Web

www.ufpi.com

Course Number

ufp06a

2007 Universal Forest Products. The material contained in this course was researched, assembled, and produced by Universal Forest

Products and remains their property. Questions or concerns about the content of this course should be directed to [email protected].

An AIA Continuing Education Program

Credit for this course is 1 AIA HSW CE Hour

Ron Blank & Associates, Inc. 2009

Please note: you will need to complete the conclusion

quiz online at ronblank.com to receive credit

An American Institute of Architects (AIA)

Continuing Education program

Approved Promotional Statement:

Ron Blank & Associates, Inc. is a registered provider with The American

Institute of Architects Continuing Education System. Credit earned upon

completion of this program will be reported to CES Records for AIA members.

Certificates of Completion are available for all course participants upon

completion of the course conclusion quiz with +80%.

Please view the following slide for more information on Certificates of

Completion through RBA

This program is registered with the 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 or Ron Blank & Associates, Inc. of

any material of construction or any method or manner of handling, using,

distributing, or dealing in any material or product.

An American Institute of Architects (AIA)

Continuing Education program

Course Format: This is a structured, web-based, self study course with a final exam.

Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour Completion Certificate: A confirmation is sent to you by email and you can

print one upon successful completion of a course or from your

RonBlank.com transcript. If you have any difficulties printing or receiving

your Certificate please send requests to [email protected]

Design professionals, please remember to print or save your certificate of completion after successfully completing a course conclusion quiz. Email

confirmations will be sent to the email address you have provided in your

RonBlank.com account. Please note: you will need to complete the conclusion quiz

online at ronblank.com to receive credit

There are many factors to consider when designing a floor system

with engineered wood joists. Review the design strategies, code

requirements, different types of engineered floor components, and

their capabilities and limitations.

Course Description

Course Objectives

Upon completion of this course the design professional will be able to:

List the factors to consider when designing floor systems

Explain the appropriate design strategies for code requirements and client

satisfaction

List the types of engineered floor components, their capabilities, and limitations

Explain the Engineering, design, and support available from manufacturers

The advent of engineered wood framing

components has impacted floor system and

subsequent building design

Engineered products use wood fiber more efficiently and permit the use of

former waste fiber for new structural components with greater strength than solid sawn lumber.

New configurations with I shapes and triangles result in products with greater strength than solid sawn lumber.

Because of this new strength, design

professionals now have greater design

flexibility and opportunities for designing

larger open spaces.

This new strength also produces new

construction efficiencies through fewer

components and faster installation.

Impact of Engineered Wood

on Floor System Design

Designing floor systems

with engineered wood

components requires new

considerations by design

professionals.

In addition to safety considerations addressed

by the model building

codes, user comfort and system performance with

regard to deflection,

vibration and sound

transfer must now become

integral factors in

designing floor systems.

Designing floor systems with engineered wood

products requires attention to three sets of

considerations:

1.Requirements of the applicable model building code with regard to safety factors.

2.Practical considerations including product availability, ease and speed of installation, and design flexibility.

3. Comfort factors that may have impact on the physical and psychological well-being of those who will occupy or visit a

building.

Lets look at the various design considerations within each of these categories.

Design Considerations:

Building Code Requirements

Design Safety Factors:

Length of Span Loading Conditions Deflection Criteria Joist Spacing Fire Endurance Seismic Performance Local Regulations


Safety Factor: Length of Joist Span

Length of span, while not specified by the building codes, is certified and

published by joist and truss manufacturers and is recognized by the model

building codes in product evaluation reports. Published spans may be used

by design professionals within the specified loading and spacing

parameters.


Safety Factor: Length of Joist Span

Length of the joist span is determined by the designers space concepts and the locations of bearing points in a structure. Designers often relocate bearings to accommodate span capabilities. Once a desired span has been identified, it must be considered in context with loading conditions, deflection characteristics, joist spacing and bearing size. Consult manufacturers literature and software to confirm the appropriate joist span for given conditions.


Safety Factor: Loading Conditions

Three types of loads may apply to any floor system:

Live Loads Dead Loads Special Loads (Line, Point, Area) Live Loads are temporary loads and are defined by the building codes according to the intended use of the structure. Dead Loads are permanent loads and are comprised of the actual weights of materials that make up the floor/ceiling system. Special Loads are permanent and are actual design loads occurring on confined areas of a floor system.



Live Loads:

Live Load conditions consider temporary loads uniformly

applied to the floor system (people, furniture and moveable

items) and are specified by the building codes according to the

designated function of the space, i.e.:

Residential Living Spaces: 40 PSF Office Use: 50 PSF Retail Use: 80 PSF Assembly Areas: 100 PSF



Dead Loads:

Dead Loads are permanent, non-moveable elements (floor framing and

decking, ceiling finish, mechanical systems, insulation, etc.) and loading is

determined by the sum of the weightsper square footof all these elements. Dead Loads are applied uniformly to the floor system.

Common design practice uses standard Dead Load factors of 10, 15 or 25

PSF depending on the makeup of the floor/ceiling envelope.



Special Loads:

Line, Point and Area Loads are permanent and represent concentrated

loads on specific limited areas of a floor system. They are not applied

uniformly. These special loads may result from roof framing, interior bearing

walls, large mechanical units, large fixtures, etc.


Safety Factor: Deflection

Deflection is vertical movement of a floor system when subjected to loads.

The Building Code specifies Deflection Limits for floor systems:

L/360 Live Load Deflection and L/240 Total Load Deflection

(L is joist length in inches)

Example:

Joist Length of 20 (L= 240) 240 divided by 360 = .67 inches allowable deflection under full load

condition

Deflection limits are based on historical performance and are specified by

the codes for user comfort and to prevent cracking of ceiling and flooring

materials.



Deflection performance of a floor system is determined by three factors:

Length of Joist Span Loading Conditions Stiffness of the Framing Member (joist) Of these three, Length of Joist Span has the greatest impact on deflection.



Floor system deflection can be reduced in several ways:

By reducing Loading (by decreasing the on-center spacing of the joists) By reducing the Joist Span By increasing the Joist Depth By upgrading Joist size or materials:

Larger dimension flange or chord Higher lumber grade of components Use of engineered materials


Safety Factor: Joist Spacing

The building code does not specify on-center joist spacing but does require

spacing that will produce specified deflection performance for the loading

conditions.

Joist spacing is most often determined by owner/builder preference or the

desire to value engineer the floor system.

Traditional joist spacing is 16 o.c.

Stronger engineered joists have made possible new on-center spacing

options of 19.2 and 24.

The building codes set only minimum requirements for floor system

performance.

Value engineering recognizes the ability of fewer, stronger joists to meet

code minimums.


Safety Factor: Joist Spacing

Joist spacing must be considered along with loading conditions and length of

span when designing to achieve desired deflection performance.

Floor system performance may be enhanced by designing for higher

deflection limitations, especially for longer spans.

Since loading conditions and length of span cannot normally be changed,

Joist Spacing is the element most often changed to achieve desired

deflection performance.


Safety Factor: Fire Resistance

Building classification and building codes determine if floor systems must be

designed to meet minimum fire resistance requirements.

Multi-Family and institutional residences most often require separation of

living units by fire resistant floor/ceiling assemblies.

Single-Family residences with integral garages often require separation.


Safety Factor: Fire Resistance

Minimum standards for fire endurance are specified by building codes to

allow adequate time for building occupants to escape during a fire and for

firefighters to extinguish fires.

Floor/ceiling assemblies are designed to endure in a fire for a specified

duration of timeone, two, or more hours (depending on the code requirement).

Assemblies are tested for fire endurance by independent third-party testing

agencies using ASTM standard test designs and procedures.

Once certified, endurance assemblies are published by component product

manufacturers and by certification agencies.


Safety Factor: Seismic Performance

Individual floor joists cannot be rated for a

specific seismic zone since they only act as

components of a lateral-force-resisting

system.

Joists act as drag struts or chords in lateral-force-resisting systems such as shear

walls.

Designers must be aware of the required

forces a drag strut must carry and refer to

manufacturer data for the products drag strut capabilities.

Drag Loads are normally specified by the

building designer on construction plans.

Building Code Requirements: Local Regulations

A few local jurisdictions prohibit the use of specific engineered wood framing products. Some local codes specify more stringent deflection limitations for floor systems than the model building codes permit. Some municipalities have fire protection regulations requiring the use of sprinkler systems and/or baffling in floor systems. Fire endurance requirements may also vary by jurisdiction. Design professionals must be aware of these local regulations when designing engineered wood floor systems.


Because SAFETY is the primary purpose of model building code

enforcement, adherence to code requirements is the responsibility of all

the following:

Design Professionals

Project Developer

General Contractor

Framing Contractor

Mechanical Trades

Building Inspector

Design Considerations: Logistical Factors

Several elements of practicality must be considered when choosing the type

of framing product to be used in an engineered wood floor system, including:

Installation of Mechanical Systems

Construction Timetable

Product Access

Cost


Installation of Mechanical Systems

Electrical, Plumbing, HVAC:

Is it necessary or desirable to contain mechanical

systems within the floor/ceiling envelope (due to building

height restrictions, basement headroom, etc.)?

Is it necessary or desirable to frame bulkheads for duct

runs (may also be a design element)?

Is the construction schedule impacted by mechanical

systems installation time?

Is there likelihood of error when joists are altered to allow

mechanical systems penetrations?

Do MEP requirements and fixture placement dictate joist

depth and spacing?


Construction Timetable:

Will floor framing materials be shipped on a schedule to conform with job

site progress?

Is it reasonable to expect timely and efficient installation of floor system

components?

The pace of construction obviously

impacts project cost.


Product Access:

Are there dependable local sources

of supply for engineered wood

products?

Do suppliers offer competent

technical support for the

engineered products they offer?

Is there confidence that supply

issues will not result in down time at the job site?


Cost:

Installing the strongest, best performing

floor system for the lowest cost is

everyones natural objective.

The installed cost of a system that meets

both structural and performance

requirements is the standard of

measurement used to judge the success of

a floor system design.

Design Considerations: Comfort and Performance

Two floor system factors have significant physical and psychological impact on individuals who inhabit or use a building. Those factors are:

Sound Transmission &

Floor Vibration While these factors may, in fact, be measured quantitatively, reactions to

them by humans are purely subjective. For this reason, design professionals should be aware of human preferences for performance with regard to these factors.


Sound Transmission:

Sound transmission refers to how easily sound is transferred through an elevated floor system.

Some code bodies set requirements for sound performance by specifying minimum standards for Sound Transmission Class (STC)

and Impact Insulation Class (IIC).


Sound Transmission:

STC and IIC ratings are determined by the testing and certification of floor/ceiling assemblies by independent third-party agencies.

Codes and designers specify minimum STC and IIC ratings for floor systems to satisfy the majority of people who occupy or use a

structure.

It remains a fact that human reactions to sound transmission are totally subjective in nature.


Sound Transmission:

Manufacturers of engineered wood floor framing components and third-party agencies publish sound performance assemblies for reference by

designers.

To maintain sound performance requirements, construction details must be followed accurately so that assemblies are not compromised

by penetrations, etc.


Floor System Vibration:

Vibration is oscillatory movement of the floor system when subjected to a live load such as footsteps, a dropped item, or machine vibration.

Floor vibration performance is the least quantitative and most subjective characteristic of a floor system.

Vibration performance should be a priority.

consideration for floor system designers.



Studies have shown that excessive floor system vibration makes occupants uncomfortable and may even cause them to fear system

failure.

It is also known that auditory effects (rattling china closets, etc.) heighten human discomfort with vibration.

Vibration is not necessarily related to the structural integrity of a floor system and extra design measures may be required in anticipation of

satisfying end users.



It should be recognized that floor system vibration is a performance concern, not a safety issue.

U.S. building codes do not specify vibration performance requirements for floor systems.

It should also be recognized that vibration is not simply a side effect of deflection.



Three factors influence human response to floor system vibration:

The Frequency Content of the vibration

The Amplitude of the vibration

The effects of vibration Damping



Frequency Content is the cycle time of the vibration, measured in cycles per second or hertz, Hz.

Humans feel more comfort with higher frequency vibrations than lower Hz cycles.

Shorter lengths of span have higher frequencies than long lengths of span.



Amplitude is the magnitude of floor vibration.

Amplitude is directly related to the stiffness of the floor (deflection).

High amplitude vibrations are more annoying to people than low amplitude

vibrations.



Amplitude may be reduced by two methods:

Specifying deeper framing members (joists)

Using bridging between joists Continuous bridging perpendicular to the

bottom flange of the joist is the most effective.



Damping of vibration reduces amplitude and shortens the duration of

vibrations.

Damping is provided by existing loads and frictions within the floor system.

Damping is achieved with bridging and through the presence of interior

partition walls.

Design Strategies

To determine the proper design strategy for a project, the design

professional must consider building classification, safety factors, comfort

factors and cost.

These considerations will lead to

one of two basic design strategies:

Code Minimum Strategy

Client Satisfaction Strategy

Design Strategies

Code Minimum Strategy:

Most often, this strategy is identified as the

Value Engineering approach. In this design strategy:

On-center joist spacing is maximized and long spans are accommodated

Quantities of framing materials are minimized and installation time is reduced

The installed cost of the floor system is minimized

Design Strategies

Client Satisfaction Strategy:

The classification of a building normally dictates the application of this strategy.

Custom residences and other privately

commissioned projects naturally demand

a client satisfaction design strategy.

This strategy gives high priority to comfort and performance factors when designing

floor systems and usually specifies

structural performance in excess of that

required by the building codes.

In this strategy, cost is usually not of primary concern.

Engineered Wood

Floor Framing Components

Now lets consider the engineered wood floor framing components available in todays market.

They include:

Floor Joists

Beams and Girders

Rim / Band Board

Hangers / Connectors

Engineered Wood


Floor Joists:

There are three types of engineered wood joists

available today:

Wood I-Joists

Steel-Plate-Connected Parallel Chord Floor Trusses

All-Wood Parallel Chord Floor Trusses

Engineered Wood


Wood I-Joists:

Invented 1969 by Truss Joist Corporation

Extensive architect education effort

I cross section

Solid sawn flanges and plywood web

Switched to LVL flanges and OSB webs in 1990s

APA-The Engineered Wood Association published standards for I-Joists in 1990s

Engineered Wood


Wood I-Joists:

Flanges resist bending, web resists shear

Lighter than dimension lumber

Efficient use of wood fiber

Consistent quality

Penetrations through web limited

Depths of 9-1/2, 11-7/8, 14, 16, 18

Multiple span applications with proper blocking

Engineered Wood


Wood I-Joists: Flange dimensions of 1-1/2 to 3-1/2

Flanges of solid sawn SPF, LVL, LSL

Installation requires accessory reinforcement pieces: web fillers, web

stiffeners, squash blocks

Can accommodate some point, line and area loads with proper reinforcement

Structural rim board is required at ends of joists

Engineered repair details required

Engineered Wood


Steel-Plate-Connected

Parallel Chord Floor Trusses:

Invented in 1952 by A. Carroll Sanford

Open web configuration

Made possible by the innovation of the steel truss plate

Steel plate values are measurable and can be sized to handle forces of

compression and tension at joints

Truss engineering software is used to design trusses for specific job

conditions

Engineered Wood




Constructed of SYP, Doug Fir or SPF lumber

Flanges of 4x2 most common

Web dimensions must be same as flange dimension

May be designed to accommodate duct chases

Must be fabricated to exact jobsite dimensions

Structural rim board is not required at ends of trusses

Engineered Wood




Can be designed to handle point, line, and area loads

Common depths are 12, 14, 16, 18, 20, 22, 24

May be damaged by excessive construction materials loads

Engineered repair details required

Engineered Wood


Proprietary Steel Plated Floor Trusses: Open web configuration

Wood or steel webs

Stock lengths with trim-able I ends

Space Joist TE, Trim Joist, Gator Joist

Depths of 9-1/4, 11-1/4, 14, 16, 18

Flanges of 4x2 or 3x2

Structural rim board required

Engineered Wood


All Wood Parallel Chord Trusses:

Invented in Canada in 1989

First trim-able open-web floor joist

Stock lengths in one-foot increments

Combination of I and truss engineering

Values from actual testing

Engineered Wood


All Wood Parallel Chord Trusses:

Assembled with precision finger joinery and structural adhesive

No metal plates or fasteners

Spruce-Pine-Fir flanges and webs

Flanges of 4x2 and 3x2

Depths of 9-1/4, 11-7/8, 14 16

Technology allows efficient use of wood fiber

Engineered Wood


All Wood Parallel Chord Trusses: Trusses are individually tested

Standard repair details on hand

Simple span installation

Bottom-chord-bearing

1-1/2 bearing required

Can accommodate point, line, and

area loads with proper reinforcement

Structural rim board not required

Engineered Wood


Structural Rim Board:

Structural rim is designed to support vertical

loads transferring down through bearing walls.

This rim is available in several engineered wood

technologies, including:

LVL (laminated veneer lumber)

PSL (parallel strand lumber)

LSL (laminated strand lumber)

OSB (oriented strand board)

Glu-Lam (laminated solid sawn lumber)

Solid sawn lumber

Engineered Wood


Beams and Girders:

Beams and girders are manufactured with the same technologies as

structural rim board, including:

LVL (laminated veneer lumber)

PSL (parallel strand lumber)

Glu-Lam (laminated solid sawn lumber)

Steel plated girder trusses

Engineered Wood


Hangers and Connectors:

The designer must choose hangers that accommodate the

loads and reactions at the ends

of joists and beams.

Major manufacturers offer products to fit all engineered

wood joist and beam sizes.

Manufacturers provide Design Guides to help designers

choose correct products.

Design Assistance

Manufacturer Literature:

Span charts and load tables

Installation details

Fire and sound assemblies

Product specifications

Manufacturer Websites:

Repeat of printed information

Interactive for product sourcing

Downloadable details and specs

Design Assistance

Engineering/Design Software: Usually offered free of charge by

manufacturer

Training is usually provided

Design Done by Supplier: Design floor system to architects

specifications

Final approval by architect and/or engineer

Sealed shop drawings should be available from the manufacturer

Course Summary

The design professional will now be able to:

List the factors to consider when designing floor systems

Explain the appropriate design strategies for code requirements and client satisfaction

List the types of engineered floor components along with their capabilities and limitations

Explain the Engineering, design, and support available from manufacturers

Designing Floor Systems with Engineered Wood Joists

Course Sponsor

Designing Floor Systems

with Engineered Wood Joists

Universal Forest Products, Inc. 2801 East Beltline NE

Grand Rapids, MI 49525

616-365-6608

E-mail

[email protected]

Web

www.ufpi.com

Course Number

ufp06a

2007 Universal Forest Products. The material contained in this course was researched, assembled, and produced by Universal Forest

Products and remains their property. Questions or concerns about the content of this course should be directed to [email protected].

An AIA Continuing Education Program

Credit for this course is 1 AIA HSW CE Hour

Ron Blank & Associates, Inc. 2009

Please note: you will need to complete the conclusion

quiz online at ronblank.com to receive credit

Documents

ufp06a