WOOD I-JOISTS & FIREFIGHTER SAFETY -

Presentation on theme: "WOOD I-JOISTS & FIREFIGHTER SAFETY"— Presentation transcript:

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WOOD I-JOISTS & FIREFIGHTER SAFETY

Awareness Guide

Ray O’Brocki, CBOManager- Fire Service RelationsAmerican Wood Council

Purpose of this guide

The purpose of this Awareness Guide is to provide the fire service with information on the types and properties of wood I-joists, how they are manufactured and how they are used in residential construction. It is important that the fire service understand the unique characteristics of wood I-joists and recognize their unique installation requirements.

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Learning Objectives

Upon completion, participants will be better able to identify:

Identify the types and applications of I-Joists

I-Joists

Be able to identify where I-joists are most commonly used and take proper precautions

Firefighter Safety

Identify the method for the manufacture of I-Joists

Manufacture

What to look for when visiting a residential construction site and examining the framing

Site Visits

1

3

2

4

What is a Wood I-Joist?

Shaped like the letter “I”

Two horizontal components – flanges

Vertical component – web

Used primarily in floors

Also roof rafters

Long lengths and high load capacities

I-Joist Components

Close tolerance between individual components

Flanges

Solid sawn lumber

Structural composite lumber (SCL)

Webs

Oriented strand board (OSB)

Sufficient thickness to transfer loads to flanges

I-Joist Installation

Holes/Openings

Cut in the web

Allow ducts/utilities through I-joist

Must strictly follow

Manufacturers’ recommendations

Applicable building codes

Builder Appeal

Uniform dimensions

Lightweight

Long span capability

Types of I-Joists

1980s

Plywood web

Sawn-lumber flanges

1990s

OSB web

SCL flanges

Laminated veneer lumber (LVL)

Laminated strand lumber (LSL)

I-Joist Manufacturing

Web

Cut to proper rectangular shape

Edges shaped to match flange groove

Continuous process

Web edges glued

Inserted into flanges

Pressed together

Cut to length

Cured in special ovens

Develop full adhesive strength

I-Joist Use in residential construction

Depths 9-1/2 to 16 inches

Single continuous span often used

Efficiencies during construction

End-supports

Beams

Bearing walls

Intermediate supports

If needed

I-joist floor assemblies can bear on girder and column system as shown in this SF dwelling

Important performance characteristics

Strength and Stiffness

Capacity to carry design loads without Failing

Deflecting beyond specified limits

Glulam and I-Joist construction

Fife, Washington

Courtesy of APA — The Engineered Wood

Association

Important performance characteristics

Connections

Ensure proper load transfer

Gravity

Wind

Earthquakes

To the foundation

Glulam and I-Joist construction

Fife, Washington

Courtesy of APA — The Engineered Wood

Association

Important performance characteristics

Modifications

Holes for mechanicals

Published hole charts (see manufacturers’ literature)

Structural analysis

Repair or manufacturer evaluation

Holes that are too large

Flange damage

Glulam and I-Joist construction

Fife, Washington

Courtesy of APA — The Engineered Wood

Association

Important performance characteristics

Occupant Considerations

Not required in building codes

Evenness of floors

Vibration

Bounce

Floor system feel

Often important design consideration

Glulam and I-Joist construction

Fife, Washington

Courtesy of APA — The Engineered Wood

Association

Is it an I-Joist or Truss?

Often thought of as being the same

Design and installation requirements uniquely different

Parallel chord trusses

I-joists and LVL girder

I-Joist & Truss Similarities

Similarities

Share common component names

top and bottom chords (flanges)

Make efficient use of wood fiber through design

Duct work easily routed through parallel chord truss floor assembly

I-Joist Floors: Courtesy of

APA — The Engineered Wood Association

I-Joist & Truss Differences

Differences

I-joists – fixed design properties

Trusses – project-specific design

I-joists – adhesives

Trusses – metal connector plates

I-joists – deep (tall) webs require blocking

Trusses – long truss webs require bracing

I-joists – distribution channels allow long-distance shipping to job sites

Trusses – regional manufacturing

Courtesy of APA – The Engineered

Wood Association

General Construction practices

I-joists installed similar to sawn lumber floor joists

Also used as roof rafters

Careful attention to connection details and framing configuration

Bridging can be used to increase stiffness and reduce bounce and vibration

General Construction practices

I-joists must be held vertically where supported by a beam

Achieved with blocking or joist hangers

Special attention to connectors during installation

I-joist floor assembly viewed from the

floor below

General Construction practices

I-joists used as roof rafters for high, open ceilings

No ceiling joists resist outward thrust

I-joists supported at both ends

LVL ridge beam

Wall top plate

Ridge beam load

Carried by columns to foundation

General Construction practices

Similarities to traditional solid sawn assemblies

ends capped with rim joist – holds joist vertical and transfer loads from wall above

rim joist attached to sill plate that is bolted/strapped to foundation

Site visits

I-Joist Floor Framing

D

etail

Residential construction

built from ground up

Framing inspection

from roof down

Site visits

I-Joist Floor Framing

D

etail

Load path continuity

most important structural characteristic common to all buildings/construction

route that loads follow to footings

gravity

live, snow, and water ponding

lateral loads

wind and earthquake

Site visits

I-Joist Floor Framing

D

etail

Simple single-family dwellings

roof, ceiling and floor loads

collected through rafters or joists

rest on

exterior walls

interior beams

bearing walls

Site visits

I-Joist used as roof rafters

Pre-planning or Training

Layout drawings

Spacing

Connection specification and location

Proper bearing

Walls, girders, or joist hangers

Web stiffeners

Attached where specified

Hangers

Manufacturers requirements

Nail in every hole?

Screws typically not permitted as nail replacement

Field modifications

Wiring, plumbing, HVAC

Manufacturer’s recommendations

Fire Incidents with I-Joists

Exposed I-Joist Floor

System

Courtesy of APA — The Engineered Wood Association

Fire incident reports

Direct fire exposure (unprotected)

Strength loss often occurs with floor sheathing burn-through

I-joist web consumed first

Bottom flange falls from system

Resulting floor systems

Remain intact

Over 12" deflection

Firefighters

Felt a floor become "soft" or "spongy"

Visually observed deflection

Exited the structure

One of many Modern home features

Feature

Larger Homes

Open Floor Plans

Increased Fire Loads

Floor/Ceiling/Attic Voids

New Building Materials

More Synthetics in Furniture

Fire Behavior Effect

Faster Fire Propagation

Shorter Time to Flashover

Shorter Escape Times

Shorter Time to Structural Collapse

Source: UL University - Structural Stability of Engineered Lumber in Fire Conditions - Underwriters Laboratories

UL Fire Testing: Floor systems

Source: UL University - Structural Stability of Engineered Lumber in Fire Conditions - Underwriters Laboratories

Test

Protected or Unprotected

Time to Collapse

(min:sec)

2x10

16”

o.c.

Unprotected

18:45

12” deep I-Joist

24”

o.c.

Unprotected

6:03

2x10

16”

o.c.

Protected with

½” GWB

44:45

12” deep I-Joist

24”

o.c.

Protected with

½” GWB

26:45

Fire Protection of floors - IRC

R302.13 Fire protection of floors

. Floor assemblies that are not required elsewhere in this code to be fire-resistance rated, shall be provided with a

1/2-inch gypsum wallboard membrane

, 5/8-inch wood structural panel membrane, or equivalent

on the underside of the floor framing member

. Penetrations or openings for ducts, vents, electrical outlets, lighting, devices, luminaires, wires, speakers, drainage, piping and similar openings or penetrations shall be permitted.

Exceptions:

Protected by an NFPA 13D system

Floor assembly directly over a crawl space w/o storage of heating appliances

Aggregate area doesn’t exceed 80ft

2

or fireblocking separates unprotected portion from remainder of floor assembly

Floor assemblies using dimensional or structural composite lumber 2x10 or greater

Fire suppression considerations

Assume houses built after 1990 utilize I-Joist floor and roof systems

Floor collapse firefighter fatalities primarily occur over basements

Consider not putting firefighters directly on roof – work off aerial ladders

Vent through natural openings e.g. skylights and scuttles

Basement fire with exposed

ceilings

I-joists

– do not conduct interior attack unless

incipient fire stage

human life is at stake

fire can be extinguished quickly

Floor/ Roof failure is unpredictable and can occur with little or no warning

DO NOT LET LACK OF HEAT FOOL YOU

!

UL Testing revealed temperature difference above and below floor/roof system can be 968-1221˚F 30 seconds before collapse

Source: UL,

Report on Structural Stability of Engineered Lumber in Fire Conditions, Underwriters Laboratories

, Sept. 2008. Pg. 104