Close up Design and

Detail of Concrete

Buildings

Practical guidance for

sustainable construction

Gillingham House, Oct 2012

14:00 – 14-10 Introduction

14:10 -14:45 Principles of construction for heavyweight buildings.

Different systems, and relative benefits - Elaine Toogood

14:45– 15:15 Thermal mass for cooling in non-domestic buildings

– Tom De Saulles

15:15 – 15:30: Refreshment Break

15:30 – 17:00 Achieving visual insitu concrete - Andrew Cotter

17:00 – 17:30 Tea, Coffee and Sandwiches

17:30 – 18:40 Good practice detailing and specification for

sustainable construction – Elaine Toogood

18:40 – 18:50 Overview of Thermal Properties Calculator and Passive

Design Tool – Tom De Saulles

Further questions and close

Principles of

construction for heavy

weight buildings

• Performance issues

• Construction methodology

• Types of construction

• Factors effecting choice

How do we categorize

building methodologies-:

Light weight ?

Medium weight ?

or

Heavy weight construction?

Ideas Store, Hackney,

Adjaye Associates / Mott Macdonald

Ideas Store, Hackney,

Adjaye Associates / Mott Macdonald

The Hepworth Gallery,

Chipperfield Architects/ Ramboll

City of Westminster College,

Schmidt Hammer Lassen Architects /Buro Happold

City of Westminster College,

Schmidt Hammer Lassen Architects /Buro Happold

Why use heavyweight

construction?

Inherent performance of concrete:

• Strength

• Durability

• Fire resistance

• Acoustic Performance

• Flood resilience

• Robustness

• Security

• Airtightness

• Thermal Mass

• Visual appearance

Why use heavyweight

construction?

Other influencing factors:

• Cost

• Procurement

• Available skills

• Programme

• Quality

• Site conditions

• Health and Safety

• Flexibility / design changes

• Sustainability

• Design life

Precast hollow cored floor

Post tensioned floors

Composite floors

Contoured/coffered floors

Ribbed floors

Sprayed concrete

Tilt up construction

Fabric formwork

Some construction techniques

using concrete

Concrete blocks (masonry)

Lightweight aerated panels

Insulated concrete formwork

Beam + block floors

Cast insitu

Precast Crosswall construction

Tunnel form

Twin wall

Insitu construction ?

Or

Offsite construction ?

Or

Hybrid?

Construction techniques

•Cast Insitu reinforced concrete (frames, floors)

•Tunnel form

•Sprayed concrete

•Steel permanent formwork

•Concrete blocks

•Beam + block floors

Construction techniques

Pre-manufactured components

• Volumetric

• ‘Flat’ elements

Whole building systems

• Cross wall

Pre-cast elements

• Stairs

• external walls

• columns

• floor slabs

• cladding panels

Off Site construction

• Twin wall

• Composite floors

• Combination of precast

and cast insitu elements

Hybrid structures

Insitu or precast columns

Traditional v. Modern Methods of Construction (MMC)

Construction techniques

The Homes+Communities

Agency used to require such

approaches for affordable

homes funding

Include:

• Light weight aerated

panels

• Insulated concrete

formwork

• Cross wall

• Tunnel form

Modern methods of construction

• Twin wall

• Pre tensioned beams/slabs

• Tilt up construction

• Thin joint block work

Sprayed concrete

Darwin centre

C.F Moeller/

Ground floor:

•Insitu ground bearing slab

•Suspended slab

Screed

In-situ

reinforced

concrete

slab (150mm

dpm

Blinded fill

100mm

EPS

)

Trench fill

Ground floors

•Suspended ground floor and

upper floors

•Precast prestressed concrete

beams and standard building

blocks

•Range of beam depths (150 -

225mm) and block widths

•Generally spans up to 8m

Beam and block

• Key advantages:

• Voids can be introduced to reduce

self-weight

• Uses small repetitive components

• Easily handled and quick to place

on site.

• Immediately safe platforms

• Beam depths range from 150mm

to 225mm.

Beam and block

Janet Street Porter House

CZWG/

• Continuous voids to reduce

self weight and provide an

efficient structural section

• Panel depths typically from

110mm to 400mm

• Panel widths typically

1200mm wide but others

are available

• Length of panel dependent

upon the project

(4m – 16m)

Pre-cast hollow core floors

• Designed to have efficient

shear key joints between

slabs

• When grouted, the

individual slabs become a

system that behaves

similarly to a monolithic

slab

• Often pre-stressed to

improve span

• Min 200mm for shared

bearings before ties are

required

Pre-cast hollow core floors

Continuous wet mortar

to take up camber

Min 140mm bearing with

grouted reinforcement ties

Key advantages:

• Range of spans and loadings

• Precasting reduces time on site

• Immediate safe working

platform

• The soffit can be exposed or

simply treated

• No propping or formwork on

site

• Thermal mass potential

Pre-cast hollow core floors

National trust HQ, Swindon

Fielden Clegg Bradley Studio /

• Insitu flat slab

• ‘traditional’ steel reinforcement

(spans 4 - 12m)

• Post-Tensioned Slabs

(spans 6 -14m)

Cast insitu floors

Key advantages

• Speed of construction

• Simple and fast formwork

• Flexible plan for partitions

and services

• Can aid daylight

• Simple services installation

• Pre-stressing can improve

spans and material efficiency

further

Flat slabs (aka solid slabs)

Environmental benefits:

– Less concrete

– Reduced use of raw

materials

– Reduced lorry movements

Rapid construction:

– Larger pour area for same

volume of concrete

– Less traditional steel

reinforcement

Post-tensioned Concrete Floors

Minimum floor thickness

– Minimises the self-weight and

foundations

– Up to 300mm less than steel frame

– Cladding area is minimised –

reducing cost.

– Reduces solar gain

Long spans

– Less columns and foundations

– Increased flexibility for space

planning

– Maximises net lettable area

Potential for an extra storey in

a ten-storey building.

Post-Tensioned Concrete Floors

Flat slab with column heads:

• Supports higher loads and reduces

thickness of rest of slab

• Cost effective 5m – 10m spans

One-way flat slab with beams

• Beams in direction of longest span

• Upstand beams typical around

perimeter to maintain daylight

Flat slab options

One-way flat slab band beams:

• Can be economical for columns

size for structures with light loads

• Thinner slabs

2 way flat slab with beams:

• Common for high loads and

limited services (eg warehouses)

• spans 4-12m

Flat slab options

Ribbed slab with beams:

• Reduces self weight with

increased surface area

• 6 – 14m spans, and slightly deeper

Trough slab

• Similar to ribbed, but included

integral band beams

• spans 4-12m

Other insitu floors

Waffle slab

• Uses less concrete with deeper

slabs

• Distinctive profiled soffit with

increased surface area

• 7 – 14m spans

• Higher formwork costs and longer

construction times

Other insitu floors

Steel Deck Composite Floors

• Decking acts as permanent formwork

to the concrete, and provides

sufficient shear bond with the

concrete, so that the two materials

act compositely together.

• Principally for use with steel frames,

but can also be supported on brick,

masonry or concrete components.

• Reinforcement can be traditional

mesh or steel fibres

Hybrid Construciton

• Precast concrete as permanent

formwork to insitu topping

• Eg: Twin wall; lattice girder

floors; omnia deck

• Composite floors using lattice

girder normally consists of a

temporarily propped pre-cast

plank which is not pre-stressed.

Twin Wall construction

• This contains most of the

bottom reinforcement in

addition to the lattice

girder.

• Plank depths typically

range from 50mm – 100mm

• Finished overall depth

between 115 – 250mm

• Plank widths are usually

either 1200mm or 2400mm

• Depending on loadings and

overall slab depth, spans of

over 11.0m can be

achieved.

Spray on Plaster Finish

Pre-cast Plate

• Panels craned into

position from the

delivery truck

• Panel weight

determined by

dimensions and number

of door/window openings

• 5 m long by 2.7 m high

panel will weigh approx

3.7 tonnes

Construction

• At corners the outside skin

of the double wall panels

project beyond the inside to

provide a fully “shuttered”

junction

• All vertical joints are sealed

with foam filler or wood

Twin wall

• Steel projecting from the

wall acts as a starter bar for

the next wall lift

• The timber kicker shutter

seals the 30 mm horizontal

gap at the base of the wall

• In filling the wall void the

concrete is driven out under

the wall plates to fill the

nominal 30 mm gap and

ensure full contact bearing

for the structural wall

Construction

• Erection sockets are cast

into the face of the wall

panel for a rapid

connection of the push pull

props

• Note where the outside

face of the panel extends

on up to act as a shutter

for the edge of the floor

slab

Construction

Self finished walls to

receive spray on thin

coat plaster

Structure Ready for Finishes

• Precast permanent shuttering

• Hollow spheres (recycled high

density polyethylene) trapped

in reinforcement cages above

concrete biscuit

• Reduction in concrete usage by

approximately one third

• Opportunity for exposed soffits

• Precast reinforced panels upto

~ 2.4 x 9m

Permanent void formers

• Prefabricated, lightweight formwork system for cast insitu concrete

• Different systems available:

– Block

– Plank

– Panel (Twin wall)

• Variety of fixing methods and systems

Insulated Concrete Formwork

(ICF)

• Polystyrene insulation is used as

permanent formwork for the

concrete

• Provides monolithic structure

• Pour heights limited – usually

require additional falsework

• Very simple assembly

• Cold weather working

Insulating Concrete Formwork (ICF)

Masonry (blockwork)

‘Traditional’ construction

• External walls

• cavity construction

• partial/full fill

• brick or block outer leaf

• Internal partitions

• Basement walls

• Separating walls

Walls

• Modern method of

construction

•Special dimensionally

accurate aerated blocks

• Specific thin-joint mortar

• 2-3mm joints

• No pointing necessary

•Independent of brickwork

provides programming

benefits

Walls: thin joint masonry

Prefabricated cavity wall system

• Rapid on-site build

• Consistent quality in controlled factory conditions

• No on-site wastage

• All weather construction

• Any combination of brick and blocks and any brickwork bond

• Higher resistance to rain penetration

• Immediate finished envelope and façade

Quickbuild™

• Structural or as cladding

• Rainscreen or waterproofing finish

• Insulated sandwich panel options

• Range of finishes possible

Walls: Precast

Athletes Village

Crosswall construction

• Pre cast cellular building

system

• Particularly appropriate for

residential sectors including

hotels, student residences

• Comprises factory

engineered concrete

components including:

• Loadbearing walls

• Floors & Ceilings

• Lift Shafts and stair

• Elevation panels

Crosswall Construction

• Prestressed flat

slabs spanning from

cross wall to cross

wall

External walls

with window

openings

Internal

dividing walls • Floor slabs are

stitched together

and act as a

diaghram providing

lateral stability

Ties in

every unit • Walls are stitched

together to form

load bearing joints

Buildability

Construction and Design benefits:

• Less infill wall panels

• High quality finishes minimises

follow-on trades

• Flush walls and ceilings – no

downstands or columns

• Tight tolerances

Construction

• Precast concrete panels are

delivered directly to site in

line with the construction

programme

• Units are lifted directly from

the delivery vehicles into

place

Insitu-stitching carried out on site using reinforced

bar and a high strength non-shrink grout

Fixing Detail

Fixing and Inspection Detail

• Repeated elements will be

erected off foundations or a

transfer slab

• Scaffolding not always

necessary

• A movable safety netting

system is secured to the

concrete frame which moves

with the construction of each

floor

For optimum solution try to

minimise number of

panels. This depends on:

• Crane capacity at precast

yard

• Crane capacity on site

• Site access

• Maximising number of

units on lorry

• Transportation limits

University of East London, Fraser Brown MacKenna architects

Five seven-storey and four three-storey structures

3,526 precast panels

Constructed in 33 weeks

•Time on site v time to design

•Co-ordination of trades

•Phasing of works

Programme and Resources

Cost model studies

www.concretecentre.com/publications

Flexibility/Design changes

•Time available to fix brief and design prior to start on site

•Future adaptability: on site and post occupancy

New Square, London

Bennetts Associates

Cost

• Materials

• Labour

• Transport

• Programme

• Compare like for like

ie Include all additional finishes

Independent study

•Architecture plb

•Arup

•Davis langdon

•Costain

• 6 structural

options considered

•Published 2008

Secondary School – 1400 Pupils

16,000m² of gross external Area

Mix of 2 & 3 storey spaces

Ground Floor Plan

Cost model study - school

Less than 2% cost variation

Cost model study - office

Procurement

•Design responsibility and quality control

•Specialist items

•Specialism of different contractors

Site Conditions

•Location

•Access for delivery

•Possible crane size and location

•Size of site (for storage)

•Local labour force

•Weather conditions / exposure

Quality

•Design brief

•Fair faced finish

•Control and responsibility

•Workmanship

Buildability

•Appropriate designs

•Sequence of works

•Skills/labour to match requirements

•Space for working

•Falls from height

•Edge protection

•Safe access

•Heavy lifting

•Repetitive lifting

Health and Safety

Sustainability issues

•Use of thermal mass

•Waste

•Use of recycled material in specification

•Use of local and responsibly sourced materials

•Design for future re-use or recycling

•Long term performance