STONE

INCITYTHE

Dr Tim Yates

BRE Ltd

There’s no such thing as bad stone – only badly used stoneTim Yates, BRE

12th March 2008,

Stone in the City,

The Natural Stone Show 2008

Where do we begin ?

• Choosing by appearance – colour, texture, etc

• Meeting a required performance – strength, durability

• Performance or prescription?

• Trial and error?

• Past performance

• Testing and assessment

How many types of stone are available?

• Locally – for example Bath Stone

–About 6

• Nationally – for example UK

–Around 250

• World Wide –

–Over 8000

Where do we begin ?

Stone properties

Project needs

Stone properties

Project needs

Project needs

Stone properties

Failure!

At the limit!

Success!

Variable

FixedVariable

Fixed

How do we match a stone to a project?

• Failure mode effect analysis

– What can go wrong?

– What can we test for this?

– How can we manage the risk?

• Is it safe?

• Will it last?

• Is it strong enough?

Specifying by experience

Local Stone

Trial and error Observation

Experience Measurement

Traditional Use Testing

Classification

Portland Stone in London

- observation of balusters on buildings in Whitehall

- failure of stone at the Palace of Westminster

Performance versus Product specification

Example 1:

• Resistant to 10 m/s wind loading

• 70mm thick cladding

• London limestone

Performance versus Product specification

Example 2:

• “Durable” for 50 years

• Weathering rate 2mm per 100 years

• Class B

• London limestone (based on tradition)

Product specification

• BS 8298: 1994 Design and installation of natural stone cladding and lining– Use stone like this and it will be alright

• BS 680: 1971 Specification for roofing slates– Use slates that pass

(Now replaced by BS EN123630

• BS5385 Part 5 :1994 Wall and Floor Tiling: Design and installation of terrazzo tile and slab, natural stone and composition block flooring– Doesn’t matter what you use as long as you do it right

Different types of test (1) • Index tests

– Petrographic description– Porosity, Density and Water Absorption– Saturation Co-efficient

• Strength tests– Compressive– Flexural– Modulus of Rupture– Strength around a fixing– Point load

Different types of test (2) • Durability tests

– Freeze-thaw resistance– Salt resistance– Thermal Shock

• Safety– Slip and skid resistance

• Component tests– Wind loading– Fire– Impact

Deterioration of natural stone

• Erosion and spalling• Large, solid stones• Loss of strength• Thermal and moisture

cycles• Biological growths• Westminster Abbey,

London

Deterioration of cladding

• Bowing and distortion of marble cladding

• Large, thin panels• Loss of strength• Thermal and moisture

cycles• University Library,

Göttingen, Germany

Deterioration of cladding

• Bowing and distortion of marble cladding

• Large, thin panels• Loss of strength• Thermal and moisture

cycles• Finlandia Hall Helsinki• Amoco Tower

Chicago

Different uses of stone in construction

External Cladding

External Cladding

External Cladding

Different uses of stone in construction -

Flooring and Paving

Different uses of stone in construction -

Roofing

Roofing

Roofing

Roofing

Roofing

Roofing - does something always go wrong?

Vimy Ridge

Vimy Ridge

Will the stone do what I want it to do?

Stone in different environments

Is the stone what I wanted?

A few pointers

• Select the stone with care– Establish what performance requirements of the

project– Recent test results – Assurance that the material is consistent – Extra tests if needed

• Workmanship– A good contractor– Sorting– Laying

• Any questions?

Some conclusions

Performance

Life time

Realism

Thank you for your attention