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components have inherent fire

resistance the reliance on appro-

priate detailing and workmanship

is reduced.

Precast concrete for housing

in the UK historically suffered

from an image problem, due in

part to the poorly maintained

‘brutal aesthetic’ of much of the

mass housing put up in the 60’s

and 70’s. While new housing is

still more likely to be built from

concrete than any other material,

the concrete is likely to be hidden

on the inside of the building, with concrete constructed

to higher structural and quality standards.

Furthermore, external precast concrete panels, with

a range of potentially different aesthetics, are often

designed to look more like stone than concrete, hence

the name ‘Recon’. The elaborate and elegant examples

of precast concrete cladding used for much of the East

Village Stratford (formerly the athletes’ village for London

Olympics) are a good example and I am sure that many

residents are unaware that their buildings are clad in

concrete and not stone.

The range of finishes available in concrete is very

broad, so it is wise to establish the required standard of

finish and tolerances required with manufacturers before

tender in order to align the clients and designers expec-

tations with the right product or specification.

Improved thermal performance requirements have

also lead to an evolution in the detailing of housing. To

achieve the low air permeability required of current

building regulations or passiv haus standard, designers

and constructors now need to pay closer attention to

the joints and junctions of a buildings enclosure.

This is facilitated by the solid, straight edges of pre-

cast panels, around window openings for example.

Windows can also be pre-installed and tested in the

panels. Since concrete itself is effectively airtight a pre-

cast concrete inner leaf offers a simple and durable

solution for long term airtightness.

Greater thermal insulation is provided and large cold

bridges can be simply avoided by continuing insulation

over the ends of floor slabs. In the manufacture of in-

sulated sandwich cladding panels, low conductivity con-

nectors are used to tie the two leaves together.

While much of the precast concrete used in construc-

tion is part of the structure, and is not on show it can

be manufactured to be left exposed as a final finish,

either inside or outside a building.

Since structure tends to be located inside of the

insulation and waterproofing layers, a concrete structure

provides the opportunity to ‘design out’ the use of

additional internal finishes such as suspended ceilings,

wall linings or carpets without compromising the fire,

structural and often acoustic requirements. There is a

reduction in waste generated by avoiding these subse-

quent trades.

Exposed concrete on the inside of a building also

offers opportunities to utilise its thermal mass. When

used as part of a low energy strategy, with adequate

ventilation, concrete can help improve internal thermal

comfort; reduce the risk of overheating and lower energy

bills.

This saving in energy can also significantly lower the

carbon footprint of the building over its life time. When

taking into account the savings in embodied CO

2

of the

avoided finishes and air conditioning and their periodic

repair and replacement over the life of the building this

adds up to a low whole life carbon solution for buildings

using concrete.

The Concrete Centre will be launching a new publi-

cation at Ecobuild this year, explaining the CO

2

saving of

concrete through every stage of construction, including

manufacture and demolition. Using thermal mass is an

excellent way to optimise the use of precast concrete

for sustainable construction, but there are also other

many sustainability issues worth considering. These

include long life, climate change adaption, flood resil-

ience, recyclability and recycled content, local manufac-

ture and local, responsibly sourced materials. For addi-

tional information on the inherent sustainable credential

of precast concrete refer to ‘Sustainability Matters’ an

annual publication by British Precast.

So concrete is a great starting point when considering

material selection for new buildings. It provides advan-

tages during construction as well as offering long term

performance benefits for occupants and building

owners.

• [END]

Contractors World UK & Ireland Vol 6 No 1

27

©Photo: Michael Schmahl

Hollow core precast concrete

stabs are used extensively with-

in Europe.

Contractors World UK & Ireland