Cladding by Burlington - RIBA Product Selector · PDF filebuildings has a long history ......

RE

GISTERED

FIR

M

Cladding by BURLINGTON

CI/SfB

March 2002

(41) Se5

This brochure describes the use of Burlington stone as externalwall cladding and internal wall lining to achieve a natural finishwhich will last the lifetime of a building.

Stone by Burlington was formed by the progressive deposition offine silt during the Silurian age. The deposits weremetamorphosed by intense heat and pressure within the earth’scrust, creating a totally waterproof non-porous material with a finecompact texture and great strength.

For over three hundred years Burlington has quarried this naturalmetamorphic stone from the heart of the English Lake District.Architects and designers around the world have long takenadvantage of its natural beauty, durability and adaptability tocreate classic weather-resistant details and surface finishes.

Benefits of natural stone

The richness and character of natural stone impartweatherproofing, durability and prestige to any building. With itsgreat strength and natural beauty, Burlington natural stone offersunique advantages, it is:-

• of excellent appearance;

• hard, dense and very durable;

• impervious to water;

• resistant to frost, acid rain, salt attack and pollution, cycles of wetting and drying, and extremes of temperature;

• colour-fast – will not fade on exposure to UV light;

• chemically inert – compatible with all other building materials;

• resistant to (and will not support the growth of) mosses, lichens, algae or fungi;

• non-combustible;

• self-cleansing – very little maintenance required.

When correctly detailed and installed, Burlington stone claddingand linings have a service life in excess of one hundred years. The performance characteristics of the material have beendetermined by extensive testing and are given on separateProduct Data sheets available from Burlington.

Cover photo: Aronoff Center for the Arts

STONE BY BURLINGTON

2 Cladding by BURLINGTON

Burlington’s quarries produce five distinctivetypes of stone, all of which are suitable forcladding and lining applications:

• Elterwater: a pale green stone;

• Bursting Stone: an olive green stone;

• Broughton Moor: a mid green stone;

• Brandy Crag: a silver grey stone;

• Blue Grey: a blue grey stone.

With the exception ofBlue Grey, which is an eventone throughout, each stone ishighlighted by contrasting veinswhich emphasise its naturalorigins and add character toany facing application. When combined in a singlescheme the different typesblend harmoniously, providingcomplement and contrast.

The variety of surface treatments which can beapplied to each stone increases the range ofoptions for any design scheme; those finishesinclude:

waterjet: the surface of the stone is worked withhigh-pressure water jets to give a non-slipmatt finish;

honed: a smooth finish with a slight sheen,produced by using a polishing head;

sanded: sawn stone slabs are coarsely polished;this removes saw marks and leaves a semi-smooth, regular finish;

cleft: with this traditional treatment the stone isriven along its line of cleavage to reveal thenatural grain; this gives an undulatingsurface with great character;

gritblasted: a high-pressure airline projectscoarse-grained grit onto the top surface ofthe stone producing a finish similar to cleft,but available on slabs of greater size.

flamed: the top surface of the slab is burned offusing a high temperature torch, giving anirregular textured finish;

textured: the top surfaces of sawn slabs arepneumatically tooled to produce a pitted orgrooved surface.

Burlington are continually developing the range oftreatments available. Sample cards showingmaterials and finishes can be supplied: pleasecheck the availability of a finish on a particularstone before specifying. If you require aspecialised effect we will be happy to discusswith you how it can be achieved.

Burlington stone for cladding and lining isavailable in 20mm, 30mm and 40mmthicknesses, as described in Table 4 ofBS 8298 1994: “Design and installation of naturalstone cladding and lining” (MIA DesignManual IV*: 1", 1.25" and 1.5"). To meetindividual project requirements, stone can be cutand shaped to other thicknesses and profiles ifrequired.

STONE BY BURLINGTON

Cladding by BURLINGTON 3

* Whilst the principles for specifying and installing natural stonecladding are universal, codes and standards vary betweencountries. Where variations exist the specific requirements forthe USA are given in brackets.

ÒStone is of the earth but, when it is worked, it receives the sky and becomes architecture.Ó

(Christian Norberg-Schulz)

The use of thin stone panels to *clad and *linebuildings has a long history extending from theRoman period. Over the centuries architects haveemployed stone in this fashion to achievebuildings of grace and grandeur: stone hasechoed the form of the building, emphasisedstructural elements such as columns and arches,and decorated interiors and exteriors.

*cladding refers to an external veneercovering a structure: it may include bothvertical and horizontal surfaces andcarries no load other than its own weight;

*lining refers to an internal wall coveringwhich carries no load other than its ownweight.

Advances in building technology over the lastcentury have removed many of the structuralconstraints upon the use of building materials,giving designers greater freedom in the treatmentof surfaces. Although cladding and lining areoften regarded as two dimensional, stoneremains a material with three dimensions, andthis most basic of properties can be used to goodeffect.

Historically, the functional format of stone incompression revealed itself in the finishedconstruction. In much the same way, theprinciples of masonry construction can be usedas a starting point for developing attractive facingschemes. By referring to the functionalrequirements of masonry in the shaping of thestones, the coherence of the surface treatmentcan be increased and a sense of massdeveloped.

Facing set in bonded coursing recalls the originalfunction of stone, allowing structural elements tobe defined by the treatment of the facing. Othermaterials may be introduced to counterpoint thestone and the design can be further enhanced by

variations in the finish of the panels.Plain butt joints will emphasise thecontinuity of the stone, whilst rebatedor chamfered edges will give greaterarticulation to the facing.

REALIZING THE POTENTIAL OF CLADDING


Project: Miller Performing Arts Center, Alfred University

Architect: Kallmann, McKinnell & Wood

Splashback in honed Brandy Crag

Project: Central Library, Los Angeles

Architect: Hardy Holzman Pfeiffer Associates

Cladding to escalator in honed Elterwater

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➔

The use of quoins at corners, the development ofcolumns or pilasters and the use of voussoir-likestones at openings are all references totraditional forms of loadbearing construction.

The formal and functional attributes of doors andwindows can be accentuated with jambs andreveals, allowing components to be set back fromthe wall line, thus producing shadowing andarticulating the elements. Introducing cills andstring courses adds interest to openings and hasthe functional benefit of throwing rainwater awayfrom the wall surface.

By contrast, stone cladding using moderntechnology may be used as a wrap-around skinwhich makes little reference to the underlyingstructure.

In rain screen cladding the joints betweencladding units are left open and the cavity behindthe cladding is ventilated to drain away andevaporate any moisture which penetrates thejoints. Joints can be narrow and regular, they donot have to accommodate sealants.

Stone by Burlington is more than able to meetthe exacting requirements of the modernconstruction industry, yet retains all the beauty ofa natural material – a characteristic enhanced bysensitive detailing. The stone gives a practical,hard-wearing surface, which will maintain itsappearance over centuries with virtually nomaintenance, other than periodic cleaning.

The intrinsic beauty and quality of Burlingtonstone is clearly visible to building users andpassers-by, enhancing the prestige andsignificance of any building.

REALIZING THE POTENTIAL OF CLADDING


Project: McKenna and Cuneo,Washington DC

Architect: STUDIOS

Cladding to staircase in honed Broughton Moor

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All buildings undergo dimensional changesresulting from:

• settlement

• loading

• thermal effects

Because the physical characteristics andenvironmental exposure of the cladding differfrom those of the substrate, dimensional changesproduced in the one may not be matched bythose in the other. This gives rise to differentialmovement between the cladding and thesubstrate which, if unrelieved, will produce stress,leading to distortion and/or damage.

The risk of damage can be eliminated byintroducing flexible joints between cladding units.These break up differential movement into smallamounts, the joints being wide enough to preventunits coming into contact as a result of differentialmovement. Guidance on how to assess the needfor flexible joints to accommodate expansion andcontraction of the structure is contained inBS 8298: 1994 “Design and installation of naturalstone cladding and lining” and BRE Digest 223,whilst BRE Digests 227, 228 and 229 give detailson how to calculate the extent of structuralmovement.

In principle, differential vertical movementrequires flexible joints at each floor level andabove openings, whilst the management ofhorizontal movement requires at least one flexiblejoint for every 6m (20') length of cladding:additional joints should be sited 1.5 - 3.0m fromeach corner.

The recommended width for flexible jointsaccommodating vertical movement is 10mm(0.375"), whilst flexible joints accommodatinghorizontal movement should be 15mm (0.5")wide. Where necessary the exact dimensions ofthe flexible joints can be calculated by referenceto the anticipated movement, which in turndepends upon the physical characteristics of thesubstrate and the cladding: stone by Burlingtonhas a thermal coefficient of expansion of 10.4 ´ 10-6m/˚C (a 3.0m length undergoing a50˚C temperature rise would become 1.5mmlonger). Burlington’s technical services can assistwith calculations for individual projects.

Any movement joint provision made in thesubstrate must also be carried through thecladding and lining. Cladding units which spanflexible joints must be fastened on only one sideof the joint, and supported, without beingfastened, on the other side.

STRUCTURAL MOVEMENT


Large differential movement

Movement accommodated incombined movementjoints

Cladding supportedat ground level

Cladding supportedat floor level

Floor level

Floor level

Stonecladdingwith nomovementjoints

Stonecladding withmovementjoints belowfloor level

Fastened restraint

Fastened loadbearingbracket

Mo

vem

ent

join

t in

su

bst

rate

Fastened restraint

Supported restraint

Supported loadbearing bracketchannel allows for lateral movement

Treatment of joints

Joints between cladding units can be treated inthree ways:

• All joints left open, as in a rain screen system.The effect of wind and rain penetration uponthe cladding and the substrate must be fullyassessed and the ventilation and drainage ofthe cavity properly detailed.

• All joints sealed as soft joints with flexiblesealant.

• Joints which do not accommodate movementsealed as hard joints and localised movementjoints sealed as soft joints.

Hard joints may be pointed in mortar. For jointsunder 4mm (3/16") wide a 4:1 cement:sand mortaris suitable: above that width the mortar mixshould be weaker to reduce risk of shrinkagecracks as the mortar dries. Lime gauged mortarmay also be used: the longer curing time of limegauged mortar will accommodate some initialmovement and once set it will be stronger thancement mortar.

Sealants

The prime requirement of any flexible sealingmaterial is that it retain its integrity across theentire range of changes of width of the joint.Identifying an appropriate sealing materialinvolves matching the dynamic characteristics ofthe sealant (represented by its MovementAccommodation Factor) to the predictedmaximum and minimum widths of the jointsresulting from differential movements.

Sealants differ in their properties of elasticity(ability to recover size and shape afterdeformation) and plasticity (ability to bestretched continuously and permanently).Those with predominantly elastic properties aresuitable for use with cladding materials with littlethermal inertia which respond rapidly to changesin ambient temperature. More massivecomponents, which react over days or weeks,require sealants with a combination of elastic andplastic properties.

It is essential to provide a sealant backing stripfor sealed joints: the backing strip assists in thecorrect application of the sealant by controllingsealant depth, prevents over-spill at the rear ofthe joint and provides a space into which thesealant can deform when compressed. Furtherguidance on the specification and installation ofsealants is given in BS 6213: 1982 “Guide toselection of constructional sealants”(sealants for projects in the USA should complywith ASTM C920).

The choice of an appropriate sealant and itscorrect application are vital if sealant failure is tobe avoided. A common cause of failure ismigration of fluid from the sealant to the cladding,producing dark banding at joints or streaking onthe face of the cladding. Whilst fluid migrationinitially affects the appearance of the cladding, itmaterially affects the performance of the sealant.

Burlington can advise on specific requirementsfor joint sealants.

Internal joints

Although there is no need to make themweathertight, joints in internal lining can betreated in the same way as those in externalcladding. Where joints are narrow (1-2mm) andthe anticipated movement is minimal, then theycan be pointed with neat cement, tile grout orplaster of Paris.

SEALING AND POINTING


sealant

overlap joint

stonecladding

stonecladding

sealant

non-bondingbacking strip

flush joint

stonecladding

Fixing components are the interface between thesubstrate and the facing. They may be formedof various materials such as stainlesssteel, phosphor bronze, or copperand have two main functions:

• loadbearing: totake the deadweight of thecladding or liningunits:

• restraining: tohold the claddingor lining units inposition and resistcyclic loads suchas wind pressureand suction.

Fixings may be subject to direct, bending, shearand torsional stresses, all of which must beaddressed at the design stage.

Recommended stone dimensions

FIXINGS


H

W

(d)

(t)

(d) T

20m

m

(t)

20m

m

(t)

(t)

(d)

(d)

StoneThickness

T

Min.Thickness

(t)

Min.Depth

(d)

40mm (1.5") 15mm 25mm

External cladding

Less than 3.7m above ground or floor level andcontinuously supported

20mm (1") 7mm N/A

More than 3.7m above ground or floor level

Soffits 40mm (2") 15mm N/A

Internal lining

Less than 7m above ground andcontinuously supported

20mm (1") 7mm N/A

Between 3.7 and 7m aboveground or floor level, notcontinuously supported

30mm(1.25")

12mm 20mm

More than 7m above ground or floor level

30mm(1.25")

12mm 20mm

Soffits 40mm (2") 15mm N/A

Sources: BS 8298: 1994 and (figures in brackets) MIA Design Guide IV.Local building codes and standards may specify other dimensions.

Loadbearing

Loadbearing fixings must beprovided at each floor level andover all openings in the structureor cladding. The load carried willdepend on the thickness andarea of the panels and thedensity of the stone. Cyclical orpermanent water absorption canalso affect the load, butBurlington stone’s low absorptionrate of 0.18% largely eliminatesthis consideration.

Loadbearing is commonlyachieved using recessed anglebrackets set at the bottom of theslab, or corbel plates projectinginto mortices pre-cut into theback of the stone. The requireddepth of recesses and morticesis given in the table opposite.

Combination fixings

Design constraints may requirefixings to be loadbearing whilstalso providing restraint. This canbe achieved by cranking theangle brackets or corbel plates,or by adding restraining dowelsto angle brackets. Combinationfixings should be fastened asclose as possible to the bottomof the stone.

Undercut panel anchors may beemployed where the cladding orlining is to be fixed to a steelsupport framework.

FIXINGS


alternative anglebracket with dowels to

provide restraintsimple boltedangle bracket

alternative corbel plate cranked toprovide restraint, fixed to channel

bolted corbelplate cranked toprovide restraint

angle bracketloadbearing supports

corbel plateloadbearing supports

alternative angle bracket withrestraint, fixed to channel

structural steelwork

panel anchor bolt

undercut panelanchor

Restraint

Restraint fixings maintain facing stonesin position by resisting the action offorces such as wind loading. Thedesign of restraint fixings musteliminate or minimise permanentstresses upon the stones, fixings andsubstrate.

Each facing stone usually requires tworestraint fixings at the top and two atthe bottom, although for small stonesone restraint fixing top and bottom maybe sufficient. To maximise structuralefficiency, restraint fixings should besited at 1/5 points from each paneledge, or at least 75mm from thecorner. The perimeter distancebetween fixings should not exceed1200mm.

The commonest forms of restraintfixings are ties or cramps with dowelswhich project a minimum of 20mm intodrilled holes in the slabs.

The required thickness of stone behindthe dowel holes is given in the table onpage 8. Wire ties, usually of stainlesssteel, may be used to restrain thethinner stones of fascias and linings.


FIXINGS

angle restraint bracket

alternative restraint bracket

grout in tie

alternative corner details

wire restraint

wire corner tie

channel fixed restraint bracket

top edge restraints

top edge and corner restraints

Structural fixing systems

For large scale projects the use of structuralfixing systems may be appropriate. These serveto integrate the cladding into the whole of thefacade including the glazing andinsulation panels.

Structural fixing systems may consist of:

• Grid systems with the panels mounted oncontinuous steel bearings via rebates cut intothe top and bottom edges of the stone.

• Stone cladding units installed in structurallyglazed curtain walls in similar manner to glass.

• Stone cladding units installed in glazingchannels of glazed curtain wall members, insimilar manner to metal spandrel panels.

Specialist advice should be obtained to determinewhether a proprietary system will be suitable foruse with your project.

FIXINGS


grid systemtop support

strut

top anchor

intermediateanchor

claddingjoint

intermediatesupport

bottom support

bearing tape

bottom anchor

bearing tape

attaching clip

cladding

typical layout of grid system

top support

top support

bottom support

bottom support

grid struts

structuralframe

structural glazing gaskets

metal framesurroundingstone claddingand rigidinsulation

glazing gasket

dowel

intermediatesupports

Soffits

Fixings for soffits must bear the load ofthe stone and maintain alignment. Disc bolts located in mortices in thestones both support them and allowadjustment. Other fixing methodsinclude the use of dowelled brackets,or face fixing with bolts passingthrough the stones.

The attachment of fixings

The methods chosen for attachingfixings to the substrate will dependupon the nature of the substrate andthe fixings specified. In all cases thefixings must allow for three wayadjustment to enable the stones to bealigned and levelled correctly.

Individual fixings may be attached toconcrete or blockwork substrates withexpansion bolts or resin anchors, whilstties may be grouted with mortar. Metalchannels which are either cast into orbolted to the substrate may also beused; they are particularly suitable forrestraint fixings, as the fixings canmove to accommodate dimensionalchanges in the stone.

A steel substrate may require asecondary framework to providesufficient attachment points; the risk ofbi-metallic corrosion must be avoidedthrough careful choice of materials andthe use of isolating bushes andwashers.


FIXINGS

soffit fixings

Project: Aronoff Center for the Arts, Cincinnati, USA

Architect: Cesar Pelli andAssociates, New Haven inassociation with GBBN

Cladding to staircase in honed Elterwater

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alternative soffit fixing

The range of design and fixing options is toowide to allow us to offer a draft specification, butthe project specification should cover thefollowing headings:

• Location and extent of cladding or lining.

• Loading conditions.

• Nature of substrate, including supportingstructure, cavity and insulation details.

• Supplier: BURLINGTON

• Stone: *Elterwater;*Brandy Crag; *Broughton Moor;*Bursting Stone;*Blue Grey.

• Finish: *waterjet *honed *sanded *cleft *gritblasted *flamed *textured.

• Dimensions of facing stones.

• Joints: dimensions, material.

• Flexible joints: locations, dimensions, buildingmaterials, treatment/primer/preparation,sealing material.

• Fixings: type and materials.

*delete as appropriate

Burlington’s technical advice service can assist inthe development of working drawings and adviseon fixing plans; manufacturers of proprietaryfixing systems can advise on any specificrequirements.

Grooving and chasing of the stones must bedone at the quarry, the stones reaching site fullyprepared and ready for erection.

Handling and Storage

As Burlington stone is a dense, heavy material,vehicular access should be provided to a storagearea close to the point of installation.Care must be taken on site to prevent damage tothe material; when not crated it should bestacked on edge on timber bearers and protectedwith building paper or plastic sheeting.

Health and Safety

Burlington stone is an inert material andinherently safe if handled with due caution; safe lifting techniques should always be used.Wear protective clothing to avoid cuts from sharpedges. Wear eye protection when machining,drilling or cutting. Dust produced by drymachining contains silica which can be a long-term health hazard if inhaled in significantquantities for extended periods: use a suitabledust mask.

Installation

The type and number of fixings must be inaccordance with manufacturer’s instructions andrelevant standards and building codes. Ensure site work complies with the fixingschemes, otherwise the strength of fixings will becompromised.Clean all dirt, dust and grease from jointingsurfaces. Follow the manufacturer’s instructionswhen applying sealants.Clean down work on completion, using cleanwater and a bristle brush.

MAINTENANCE

Burlington stone is durable and when correctlyfixed requires very little maintenance. Periodicallycheck the effectiveness of compression andmovement joints; renew sealants and pointingwhen they reach the end of their useful life.

Clean with water and mild detergent, finish offwith a chamois leather. For more informationrefer to BS 6270: Pt1: 1982 “Code of practice forcleaning and surface repair of buildings”(MIA Design Manual IV: specification for slate:Part VI).


SPECIFICATION SITEWORK


Prices and conditions of sale

Stone by Burlington is sold subject to ourstandard conditions of sale, a copy of which isavailable on request. We will gladly provide youwith current details of availability and lead timesand will be happy to provide firm quotations forindividual projects on the basis of drawingsand/or Bills of Quantities.

Supply, delivery

Burlington stone is normally crated and palleted:delivery in the UK is by our own road haulagevehicles, overseas deliveries will be by the mostefficient available method.

References

Burlington stone has been used in numerouscladding schemes world-wide, including:-

• Corporate Headquarters, 55 Bishopsgate, London, UK;

• Marugame Museum, Japan;

• Canary Wharf, London, UK;

• Marriot Hotel, Glasgow, UK.

Note

Recommendations as to methods, use ofmaterials and construction details are based onthe experience and knowledge of Burlington SlateLimited and on British Standards: they are givenin good faith as a general guide to designers,contractors and manufacturers.

Quality

Quality comes naturally with a material 400million years in the making and in converting thatmaterial to modern building componentsBurlington operate an ISO 9002 QualityAssurance System.

Whatever the nature of your project, Burlingtonhave the experience, the facilities and theexpertise to provide the guidance, technicaladvice and delivery schedules essential to itssuccess.

Technical support

We are always happy to provide technical adviceon the specification of Burlington stone for newbuild or refurbishment projects. We offer in-depthproject consultation and a wide range of supportservices including:

• a technical advice line: +44 (0) 1229 889 665;USA: (972) 985 9182

• estimating;

• computer-generated detailing;

• copies of relevant test results;

• product samples;

• help and advice on meeting national building regulations.

In addition, a range of technical support materialis available on request; it includes:

• Product Data sheets for the stone from eachof our five quarries.

• Sample cards for all stone tones and finishes.

• Application brochures for:

• Flooring stone;

• Interiors;

• Cills;

• Roofing;

• Burlington Natural Slate Ventilators;

• Landscaping;

• Coping stone.

Our range of stone products is continually beingextended. If you do not find your exactrequirement in this brochure please call ourtechnical advice line. We can probably supply acustomised solution for you.

The applications shown in this brochure shouldnot be treated as limits for the use of stone forcladding: at Burlington we are pleased to assist indeveloping innovative applications for our stone.


PROJECT PORTFOLIO

brochure designed by:JPA Technical Literature, Newcastle upon Tyne

(0191) 281 8393

Project: McKenna and Cuneo, Washington DC

Architect: STUDIOS, Washington DC

Cladding to staircase in honed Broughton Moor

➔

➔

Project: Barthonia Forum, K�ln, Germany

Architect: Luczak & Jurgensen

Cladding in honed and flamed Elterwater

Project: Canary Wharf, London

Architect: Cesar Pelli

Cladding honed in Elterwater

➔

Burlington Slate LimitedHead Office

Cavendish House, Kirkby-in-Furness, Cumbria, LA17 7UN, EnglandTelephone: 01229 889 661 • Fax: 01229 889 466

e-mail: [email protected]

London Office15 Queen Anne’s Gate, London SW1H 9BU, England

Telephone: 020 7976 7676 • Fax: 020 7976 0033

Web Siteswww.burlingtonstone.co.ukwww.burlingtonslate.co.uk

Soda Hall, University of California, Berkeley CAArchitect: Anshen and Allen in association with Barnes and Cavagnero

Cladding in flamed Broughton Moor

Burlington Natstone Inc.

2701-C West 15th Street, #505, PLANO, TX 75075, USATelephone: (972) 985 9182 • Fax: (972) 612 0847

e-mail: [email protected]

Cladding by Burlington - RIBA Product Selector · PDF filebuildings has a long history ......

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