the future of mass timber in construction...into effects of timber cladding • further research and...

THE FUTURE OF MASS TIMBER IN CONSTRUCTION

Webinar presentation by Chris AlleryJune 2020

STRUCTURE• Introduction• Hydrock & our fire safety division• Timeline of significant events• Timeline affecting mass timber• Types of mass timber construction• Benefits of mass timber building• Concerns • Present • Future of mass timber construction

INTRODUCTION

WEBINAR OBJECTIVESThis presentation aims to provide an update to all stakeholders with an interest in fire safety design and mass timber construction in the UK. We will discuss the following:

• Significant developments since the Grenfell Tower fire

• Benefits of using mass timber construction

• Structural design

• External Walls

• Present restrictions

• Future use of mass timber in construction

H Y D R O C K I S A M U LT I - D I S C I P L I N A R Y E N G I N E E R I N G D E S I G N C O N S U LTA N C Y.

We have over 500 staff operating from 16 UK offices including Manchester, London, Birmingham, Bristol, Cardiff, Glasgow and Leeds.

Hydrock’s Fire Safety Division was founded in 2017 and now has 25 fire safety professionals working in many of the UK’s regional capitals.

CAPABILITY• Fire Engineering• Fire Risk Management• Nuclear and Industrial Fire Safety• Expert Witness• Structural Fire Engineering• Specialist Services

The team has a broad range of expertise and experience allowing us to work on complex projects in multiple sectors.

HUN SLET ROAD(PHASE 1) , LEEDS

• Fire Engineering, Fire Risk Management & CFD Modelling Services (RIBA Stages 2-7)

• Residential development in Leeds consisting of 315 homes, commercial, retail, café and gym space

HAN GARS 85 & 86 , DYSO N, WI LTSHIRE

• Fire Engineering & Structural Fire Engineering Services (RIBA Stages 2-4)

• Fast-paced conversion of the hangars from semi-derelict former military hangars into modern, contemporary workspaces and R&D facilities for the electric car project

UWE EN GI NEERING B UI LDI NG, B R I STOL

• Fire Engineering & CFD Modelling Services (RIBA Stages 3-4)

• Featuring engine test cells, wind tunnels and dedicated learning spaces to accommodate a wide-range of engineering disciplines such as composite manufacturing, machining and metrology

• Monte Carlo and Computational Fluid Dynamics assessment

I AAPS, UN I VERSITY O F BAT H

• Fire Engineering & Fire Risk Management Services (RIBA Stages 3-7)

• New global centre of excellence, to deliver transformational Research and Development (R&D) for automotive propulsion technologies which will support the development of the next generation of low carbon vehicles

TIMELINE OF SIGNIFICANT EVENTS

3rd July 2009: Lakanal House

14th June 2017: Grenfell Tower

5th Sept 2017: Advice Note 11 Government Building Safety programme (first issue) [updated 28 Feb 18]

24th Nov 2017: Coolmoyne House Fire, Belfast

11th Dec 2017: Advice Note 14 Non-ACM wall systems (first issue) [updated 17 Nov 18]

30th Dec 2017: Light House Apartments Fire, Manchester

16th May 2018: Advice Note 16 Replacing Flat Entrance Doors [updated 31 July 18]

3rd July 2018: Orwell Building Fire, West Hampstead

28th Aug 2018: Advice Note 17 – Testing and classification of fire doorsets

28th Sept 2018: Advice Note 18 –Buildings partially clad in ACM (first issue)

17th Nov 2018: Advice Note 19 – Spandrel panels/window panels/ infill panels (first issue)

21st Dec 2018: The Building (Amendment) Regulations 2018 (comes into force)

7th Feb 2019: Advice Note 20 – Smoke Control Systems (first issue)

9th June 2019: Samuel Garside House Fire, Barking

24th June 2019: Advice Note 21 – Balconies on Residential Buildings (first issue)

18th July 2019: Advice Note 22 – Use of HPL panels in external wall systems (first issue)

30th Aug 2019: Approved Document B Volume 1:2019 (Dwellings) and Document B Volume 2:2019 (Non-Dwellings)

16th Sept 2019: Limehouse Lodge Fire, Clapton, London

15th Nov 2019: The Cube, Student Halls fire, Bolton

20th Jan 2020: ADN Advice for building owners of multi-storey, multi-occupied residential buildings

2017 20192018 20201 2

1 2

1 2

SOME SIGNIFICANT EVENTS POST-GRENFELL• The Building (Amendment) Regulations

2018• MHCLG Advice Note 22 • MHCLG Consolidated Advice Note• MHCLG Testing – HPL / Timber Cladding

TYPES OF MASS TIMBER CONSTRUCTION

TYPES OF MASS TIMBER CONSTRUCTION• Timber Frame• Glue Laminated Timber (Glulam)• Cross Laminated Timber (CLT)• Laminated Veneer Lumber (LVL) • Dowel Laminated Timber (Brettstapel)• Nail Laminated Timber (NLT)

TIMBER FRAMEInvolves the use of solid timber to form a structural frame with a similar approach to that of a steel frame

GLUE LAMINATED TIMBERIs comprised of a number of layers of dimensioned timber that are bonded together with structural adhesive to increase structural performance. Generally, the grain runs parallel to the main axis of the member.

CROSS LAMINATED TIMBERIs manufactured from lower grade timber off-cuts which are reduced to strips that are finger-jointed and glued in perpendicular layers under high pressure

LAMINATED VENEER LUMBERIs manufactured from thin, peeled veneers of wood, usually 3mm thick and glued with structural adhesive

DOWEL LAMINATED TIMBERIs fabricated from softwood timber layers stacked in one plane and connected with hardwood timber dowels

NAIL LAMINATED TIMBERIs similar to Dowel-Lam, however nails are used to connect the timber planks into a solid wood panel

BENEFITS OF MASS TIMBER CONSTRUCTION

SUSTAINABIL ITY• Resources can be expanded and replenished

through sustainable forestry management

• Timber is the only renewable construction material

EN VIRONMENT• Retains sequestered carbon dioxide

• Replacing steel with mass timber would reduce carbon dioxide emissions by between 15% and 20%

• Requires 90% less construction traffic

• Life cycle assessment studies consistently show that wood outperforms steel and concrete in terms of embodied energy, air pollution and water pollution

CO N STRUC TI ON• Mass timber buildings are roughly 25% faster to

construct than concrete buildings

• Extremely versatile construction material

• Offers greater design flexibility

• Aesthetically appealing

• Durable

CO ST EFFEC TIVENESS• Mass timber allows prefabrication so erection time

is greatly reduced improving efficiency resulting in lower capital costs

• Faster occupancy

• Reduced demand for skilled worker resource

ST RUC TURAL F I RE PERFO RMANCE• ‘Charred’ layer protects unburnt timber in fire to

maintain loadbearing capacity

• Steel loses its strength significantly over 550°C

• Compressive strength of concrete quickly lost at high temperatures above 600oC and is at risk of ‘spalling’ as low as 200oC

B EN EFITS O F C RO SS LAMI NTATED T I MBER (C LT )• Can be used as sole building materials or within a

hybrid system in conjunction with steel, etc.

• Primarily used in panels for walls, floors and roofs

• High strength-to-weight ratio providing advantages in terms of foundation requirements and uninterrupted span lengths

STADTHAUS, EAST LONDON• 9-storey residential building in Hackney, East

London

• Floors, ceiling and elevator shafts and stairwell are made of CLT

• Worlds tallest modern timber building when construction in 2009

B RO CK CO MMONS PHASE 1• Tall timber hybrid student residential buildings at

the University of British Columbia in Canada

• Consists of 18 storeys (Ground Level of concrete and 17 storeys of mass timber construction above)

• CLT floors and glulam columns

• Timber construction saved an estimated 2,400 tonnes of carbon dioxide entering atmosphere

CONCERNS

F I RE SAFETY CO N CERNS• Delamination

• Decay phase continued thermal penetration

• Fire spread via external walls

DELAMINATION• Laminated form of engineered timber combined

together by adhesive are susceptible to ‘delamination’ when directly exposed to fire

• Delaminated timber can contribute to fire load and increase heat release rate and fire duration

• Needs to be considered in design to ensure extent of exposed laminated timber will not result in risk to life safety

DEC AY PHASE CO LLAPSE• Testing suggests thermal penetration into timber

may continue after compartment fire has been extinguished

• Particularly relevant for exposed timber surfaces

• Increases potential for structural collapse during decay phase of fire

F I RE SPREAD I N EX T ERNAL WALLS• Loadbearing capacity of timber may be maintained

in fire however it WILL be on fire

• Consideration to be given in design to ensure this combustion does not result in excessive fire spread via external wall

• Limited full scale testing done to date for impact of forms of structural timber in external walls

PRESENT SITUATION

PRESENT S I T UATION• Appetite to use timber for multitude of benefits

• Banned in external walls of residential buildings above 18m

• Consultation to amend ban to 11m height threshold and include further purposes groups with sleeping risk

PRESENT S I T UATION• Designers and fire safety professionals need to

consider choice of materials used in external walls for all building types and heights

• Limited research and testing into impact of timber in external walls

THE FUTURE

SLEEPING RISK ‘BAN’• Banned in external walls of residential

buildings above 18• ‘Right Decision’ based on lack of

evidence demonstrating suitability• Cannot let the use of timber in

construction go ‘unchecked’ for life safety even considering environmental benefits

REQUIRED RESEARCH & TESTING• Further research and testing required

into effects of timber cladding• Further research and testing required

into effects of structural timber in external walls considering:

• Encapsulated / exposed timber• Various types of engineered timber

and structural framing strategies

SHORT TERM POTENTIAL IN LOWER RISK PURPOSES GROUP• Potential for use in external walls of

buildings with no sleeping risk and a simultaneous evacuation strategy

• Potential for use in any building external wall not covered by government ban subject to risk assessment

Q & A T I M E

Please use the question box to type your questions, starting with your name and who you work for.

L O C A T I O N S

BRISTOL BIRMINGHAM

CARDIFF CAMBORNE

GLASGOW GLOUCESTER

LONDON MANCHESTER

NORTHAMPTON PLYMOUTH

SOUTHAMPTON STOKE-ON-TRENT

TAUNTONWETHERBY