Fire Safety and Performance of Wood

Fire Safety and Performance of Wood

In Multi-Residential and Commercial Buildings

Fire Safety and Performance of Wood in Multi-Residential and Commercial Buildings © FWPA 2011

Learn more about wood at UTAS

Centre for Sustainable Architecture with WoodGraduate Certificate in Timber (Processing & Building)• 4 units, part time, onlineAreas covered include:• Wood science• Design for durability and service for life• Timber as a renewable resource• Sustainable design and construction• Engineered wood products• International technologies and developments• Plus, selected topics of individual interestMore information: Associate Professor Greg Nolan (03) 6324 4478 or [email protected]


Learning Objectives

After this presentation you should be able to:– Identify which Fire Hazard Properties apply in various

situations – Understand how to use timber in multi-residential and

commercial buildings– Outline the effectiveness of timber members and timber

connections during fire

For architects - AACA Competencies:– Design– Documentation


This Presentation

1. Fire Hazard Properties– Specification C1.10– Specification C1.10a

2. MRTFC and Commercial Buildings– Overview– Timber properties during fire– Connection performance during fire– Calculation methods to predict timber capacity


BCA Reference Description Section C Fire Resistance

Specifies community expectations regarding fire resistance of Class 2 -9 buildings.

Part C1Fire Resistance and Stability

Deemed-to-Satisfy (DTS) Provisions regarding fire resistance and stability

Clause C1.10 Fire Hazard Properties

DTS Provisions for Fire Hazard Properties of materials and assemblies used in the building construction industry

Specification C1.10Fire Hazard Properties – General

A method of complying with the BCA requirements for materials other than those used for floors, walls and ceilings

Specification C1.10a Fire Hazard Properties - Floors, Walls and Ceilings

A method of complying with the BCA requirements for floor coverings, walls and ceilings

Fire Resistance in the BCA


Topics

1. Fire Hazard Properties– Clause C 1.10: Specification C1.10– Clause: C1.10: Specification C1.10a



No requirementsyes

• Timber-framed window?• Solid timber handrail or skirting?• Timber- faced solid core door or fire

door?• Joinery, cupboard shelving etc.?• Paints, varnishes, etc. or adhesives

Class 1 or 10

Class 2-9

Class of Building?

Clause C1.10

Other

Specification C1.10Specification C1.10a

Covering - Floor, Wall & Ceiling no

No Clause C1.10requirements

Clause C1.10


Flammability Index

≤ 5

Spread-of-Flame Index ≤ 9and

Smoke-Developed Index2

≤ 8

Specification C1.10

sarkingAll other materials,

including timber

Materials1?

1 Additional requirements apply to fire isolated exits, public entertainment theaters, public halls etc. refer to BCA for details

2 Only for materials with a Spread-of-Flame Index > 5

Specification C1.10


More species can be found on: www.woodsolutions.com.au

Specification C1.10 – Fire Hazard Properties of Timber

http://www.timber.net.au/


Topics

1. Fire Hazard Properties– Clause C1.10: Specification C1.10– Clause C1.10: Specification C1.10a



No requirementsyes

• Timber-framed window?• Solid timber handrail or skirting?• Timber- faced solid core door or fire

door?• Joinery, cupboard shelving etc.?• Paints, varnishes, etc. or adhesives

Clause C1.10

Other

Specification C1.10Specification C1.10a

Coverings - Floor, Wall & Ceiling no

Class 1 or 10

Class 2-9

Class of Building?No Clause C1.10

requirements

Clause C1.10


Floor

Critical Radiant

Flux

Critical Radiant Flux

andSmoke

Development Rate

≤ 750 percent minutes

Specification C1.10a

Wall / Ceiling

yes no

Sprinklered?

Lift




Specification C 1.10a: Floors -Fire Hazard Properties of Timber



Floor

Critical Radiant

Flux


andSmoke

Development Rate


Group Number


Group Number and

smoke growth rate index

oraverage specific extinction area

< 250 m²/kg

Wall / Ceiling

yes no

Sprinklered?

yes no

Sprinklered?

Lift




Specification C 1.10a: Walls / Ceiling Fire Hazard Properties of Timber



Floor

Critical Radiant

Flux


andSmoke

Development Rate


Group Number


Group Number and

smoke growth rate index

oraverage specific extinction area

< 250 m²/kg

Wall / Ceiling

yes no

Sprinklered?

yes no

Sprinklered?

Lift

Group Number

1 or 2

floor wall/ceiling

Floor, Wall/Ceiling?

Critical Radiant

Flux ≥ 2.2

kW/m²

Clause Specification C1.10a: Lifts


Topics




– Multi– Residential– Timber – Frame– Construction

MRTFC

MRTFC - Overview


• MRTFC deals with: – Class 1 buildings (houses or dwellings

attached side by side)– Class 2 buildings (flats and units above one

another as well as side by side)– Class 3 buildings (residential parts of hotels,

motels, accommodation for students, aged and disabled)

– Class 9c buildings (buildings for the aged)• Performance criteria in these classes focuses on:

– Fire resistance– Sound resistance

• This presentation focuses on Fire Resistance

MRTFC and Performance Requirements


• In Class 2 and 3 residential buildings there is extensive use of “Sole occupancy units” (SOUs)This separates buildings into manageable units and provides protection for “other property”:

– A SOU is a part of a building that is occupied by one owner, lessee or other occupant

– SOUs must be designed to restrict fire and sound from affecting adjoining SOUs

SOU Concept


The extent of fire resistant construction required by the BCA depends on the Type of Construction:

Type A provides the highest level of passive protection e.g. structural elements must withstand burnout of the building contents

Type B provides lower passive protection e.g. less of the structure must be able to withstand burnout of the contents

Type C provides the lowest passive fire resistance e.g. only some elements have specified fire resistance intended to mainly restrict horizontal spread of fire to adjoining dwellings

Type of Construction


• The BCA requires protection to be provided at the boundaries between compartments or SOUs

• The walls, floors and ceilings bounding compartments are constructed to meet “Fire Resistance Levels” (FRLs) to prevent the spread of fire

• FRLs are expressed in minutes as follows:

FRL: 60 / 60 / 60 structure integrity insulation

• Columns have a FRL of 60/-/- or 120/-/- etc. as they are not barriers• Partition walls are the exact opposite: barriers but non-loadbearing so

typically have a FRL of -/30/30 or -/60/60

Measuring Fire Resistance Levels


• MRTFC details focuses on meeting the combined requirements of fire, sound and structural requirements for designated wall, floor and ceiling elements in Class 1, 2 and 3 buildings

• A systems approach is used to meet needs which can be broken up into:– Wall framing systems– Floor/ceiling framing systems

• Each system uses a number of common concepts to maintain continuity at intersections between elements and at penetrations, including:– Fire resistant joints– Cavity barriers– Fire stops

General Framing Requirements


• The system features two stud walls with a separating cavity

• Load bearing frames are typically made from 90x45 timber framing

• The frames can be prefabricated as required

• The system is easy to handle and erect onsite

• Insulation is used extensively between studs or in the cavity

• It must be non-combustible (BCA Requirement)

• Fire grade plasterboard is built up in layers to meet fire requirements

• Fibre cement sheet can be used in combination with plasterboard

• Other cladding or linings can be used over these components

Double Stud Walls in More Detail


Depending on the type of construction, fire rated walls may need to continue through the roof and eaves cavities. In these areas:

– walls must extend at least to the underside of the roof

– walls may be single skin (not double) because sound resistance isn’t required in the roof or eaves areas

Treatment of Roof and Eave Cavities


• Floor/ceiling systems are required between sole occupancy units (SOUs)

• These systems consist of floor coverings, platform flooring, floor joists, sound insulation, resiliently mounted ceiling battens and ceiling linings

Floor/Ceiling Systems


• Timber joists dictate the load and spanning capacity of the floor

• Non-combustible sound insulation is placed within the joist depth

• Resiliently mounted ceiling battens are fixed transversely to the joists to isolate sound from the structure above

• Plasterboard is fixed to the sound resilient supports. A build up of layers is used to achieve sound and fire requirements (fire grade board required)

Summary of Floor/Ceiling System Components


• Care must be taken to ensure weak spots don’t occur at the interfaces between systems (e.g. intersections and penetrations)

• Methods of doing this include:– Fire resistant joints– Cavity barriers– Fire stops at gaps and penetrations (caulking)

Continuity of Systems


• Fire resistant joints are used at intersections between floor/ceiling elements e.g. where one element has a lower FRL than the other

• Some structural framing remains protected by the plasterboard and by the slow charring of the other framing at the junction.

Fire Resistant Floor Junctions


• Needed at intersections between wall/wall elements such as when one element has a lower FRL than the other

• The joint is made by adding extra pieces of timber to the joint between the elements

• The extra timber adds fire resistance because when it burns it forms an insulative char layer on the surface – this slows burning in the core of the timber and in doing so provides fire resistance for a period of time

• In general, the more pieces of timber added to the joint, the longer the joint will last.

• In some cases light gauge steel angles are also used to slow char at corners

Fire Resistant Floor Junctions


• Cavity barriers restrict the passage of flame, smoke and gasses in cavities that bypass wall/floor/ceiling intersections

• Typical example: intersection between a wall separating SOUs and a non-fire rated external brick veneer wall

• Cavity barriers can be made by:– timber battens– appropriate sheet linings– moisture repellent mineral wool– Light gauge steel profiles

Example prior to brick veneer being laid

Cavity barrier using sheet lining

Cavity Barriers


Use fire shafts to avoid services in fire/sound rated walls

Fire Rated Shafts


Topics




Unprotected Timber Exposed to Fire


• Char can also occur within a wall or floor when protected by linings.

• Experiments show it commences later and is at a slower rate

• Distribution of char is different

Protected Timber Exposed to Fire


Topics




• Connections usually limit the capacity of a timber element

• AS1720.4-2006 – Fire Resistance and Structural Adequacy of timber members also provides guidance for the design of connections

Connections


• Unprotected metal fasteners may limit FRLs of unprotected timber

• Protection of fixings is required and can be via:o surface protection

or o embedding fixings

under plugs

• Other protection measures need test data to support their use

Connections and AS 1720.4


Topics




Charring Rate for Unprotected Timber


Depth of Char for Unprotected Timber


• Calculated based on load-bearing capacity of residual section

• Depends on density / magnitude of applied load / timber grade / dimensions

• FRLs for typical unprotected 3-sided exposed hardwood beams are shown opposite

Beam Thickness - mm FRL - min

38 14/-/-

50 25/-/-

60 30/-/-

90 60/-/-

120 90/-/-

Examples of the Fire Resistance of Unprotected Solid Hardwood


• Narrow section timber directly exposed to fire has a low FRL in accordance with AS 1720.4

• Large member sections can have significant FRLs however the connections are sometimes not protected or embedded to the same degree, hence limit the FRL to potentially a relatively low values

• Protection may be needed for these connections

Interpretation of AS 1720.4 design rules


• Protect the timber with plasterboard

Alternative Method


• Timber can be effectively used in buildings that are exposed to fire

• The key to the correct use of timber is detailing in accordance with relevant Australian standards and industry manuals (e.g. Timber Design Guides)

Conclusions


• WoodSolutions Technical Design Guides

• Updates include details for columns in walls and improved junction details

• Available by registering at www.woodsolutions.com.au

More Information

http://www.woodsolutions.com.au/


Learn more about wood at UTAS

Centre for Sustainable Architecture with WoodGraduate Certificate in Timber (Processing & Building)• 4 units, part time, onlineAreas covered include:• Wood science• Design for durability and service for life• Timber as a renewable resource• Sustainable design and construction• Engineered wood products• International technologies and developments• Plus, selected topics of individual interestMore information: Associate Professor Greg Nolan (03) 6324 4478 or [email protected]


More Information

Education

Fire Safety and Performance of Wood