Hospital Fire Design - Article

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THE Central NottinghamshireModernisation of Acute Services

scheme includes the 95,000m2

redevelopment of King’s MillHospital in Sutton-in-Asheld, Notting-hamshire, England. It includes bothrefurbishment and new-build elements.

e existing facilities are being fullyredeveloped to create a single uniedhospital comprising 28 new wards, a newstate-of-the-art diagnostic and treatmentcentre – called the King’s TreatmentCentre (KTC) – a new emergency careand assessment centre with an out-of-hours general practitioners’ service, anda dedicated women and children’s centre.Some of the new facilities are now inuse, although the project is due to befully completed in 2011.

ree T-shaped ward blocks, linkedtogether over ve oors, are located to therear of the diagnostic and treatment and

women and children’s centres. ese twomajor new-build elements are separatedby a concourse about 200m in length.

e women and children’s centre, which has its own dedicated entrance

from the main hospital concourse, isa two-storey elliptical building, whichincludes outpatient and rapid accessdepartments, as well as in-patient facilities.

e project architects are SwankeHayden Connell (SHCA), for Skanska-

Innisfree Private Finance Initiative (PFI)Consortium. Arup Fire has been involvedas re engineers in the project since theearly concept design at bidding stage,through to involvement in on-site issuesas they have arisen.

Continual consultation with the localNHS foundation trust and approvalauthorities has ensured that the uniquedesign has been able to progress withminimal risk, despite containing majordepartures from code guidance.

Challenging Firecodeis project has been the rst major

PFI healthcare project for SHCA inthe UK. From Arup’s perspective as reengineers, it has been clear from thestart that the architect’s approach todesign of the building, particularly thediagnostic and treatement centre block,has been unhindered by the ‘healthcaredesign baggage’ sometimes encountered

with designers who have been using

the Department of Health’s Firecodeguidance documents – technical resafety guidance for healthcare – for manyyears.

SHCA has extensive experience oflarge commercial developments, and

sought to combine this with the needsof a hospital. e architect’s freshapproach to healthcare design, coupled

with Skanska’s progressive constructionapproach, has challenged some of thefundamental concepts of Firecode.

is challenge to the basis of Fire-code manifested itself most strongly inthe design of the KTC block. is blockis spread over two storeys, increasing tothree storeys as the site slopes downtowards the south. e design aimsto maximise the use of natural lightby providing a series of ‘ngers’ ofaccommodation, each separated by atwo- or three-storey void space. isform of building design presented thegreatest challenges to the developmentof the re strategy.

Horizontal evacuationGuidance for the re safety design ofhealthcare buildings is given in theFirecode suite of Health Technical

Memorandum (HTM) documents. isbuilding was designed based on HTM81: Fire Precautions in New Hospitals (now superseded by HTM 05-02).

The innovative design of a hospital project in Nottinghamshireprompted major departures from the prescriptive Firecode

guidance. Andy Passingham reports

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Much of the guidance in thisdocument is aimed at the design oflarge acute healthcare facilities, and ismainly based around the movement

of bed-ridden patients in the building,using progressive horizontal evacuationto move patients horizontally throughlines of re compartmentation away fromthe re-affected zone. is produces apolicy of evacuating the compartmentaffected by the re and then using a‘defend in place’ approach to minimisethe disruption to the operation of thehospital and reduce the necessity toevacuate patients vertically, either viaevacuation lifts or by the stairs.

A key element of the ‘defend inplace’ approach is to design the buildingsuch that each storey forms a separatere compartment. e intention of thisis that it should only be necessary toevacuate a single storey of the buildingat any one time. e need for compart-ment oors was the central aspect ofthe HTM guidance that was challengedby the re strategy.

Underlying the challenge to the codeapproach is an understanding of thenature of the building. By recognising

that the operation and the type ofoccupants are very different to an acutehealthcare facility, the applicability ofsome of the principles behind HTM 81

can be examined and questioned. As thebuilding is a diagnostic and treatmentcentre, there will not be bed-riddenpatients, there are no wards, and the

level of impairment to mobility is signi-cantly lower than is assumed in HTM81. From this point of view, designingthe building around the movementof beds is less vital than the acute careareas of the hospital.

Vertical compartmentsIt is often acknowledged that the HTMguidance does not address diagnostictreatment buildings particularly well,

and this project provides a good exampleof this. e strength of the HTMdocument is that it is likely to producea conservative solution. However, whereinnovation is desired, closer examinationof the code is essential.

A conventional code-based approach would require each oor to form aseparate re compartment in the KTCblock. As can be seen in Figure 1, theopen ‘ngers’ which bring natural light

into the building are very much at odds with conventional healthcare designand the prescriptive code guidance.To achieve compartment oors in

the KTC block, each of the two- andthree-storey voids would have had tobe completely enclosed with re-ratedglazing. In addition to this, as each ofthe ‘ngers’ created a dead end, a reescape stair would be required at theend of each nger.

By working closely with thearchitects, Arup Fire developed thesolution shown in Figure 2. e guidancein HTM 81 recommends that eachcompartment is no more than 2,000m2

in area. e concept for the strategy isto take this compartment size limit andsplit it over two or three storeys usingvertical compartment lines rather thanhorizontal. In this way, the evacuation ofa single compartment would not affectany greater area than a conventionalcode-compliant solution.

is splits the building into a seriesof vertical compartments, allowingthe open oors to be provided within,

Figure 2: Arup solution using vertical compartment lines

Figure 1: Code-compliant solution –fire-rated enclosure of voids

The 95,000m2 redevelopment includes both refurbishment and new-build elements



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linking the storeys and removing theneed for compartmentation betweenthe oors. In addition to the increasedarchitectural openness achieved, thisapproach had signicant cost savingson the amount of re-rated glazing

needed, and also removed the need forre dampers on all penetrations betweenthese oors.

Linking walkwaysTo address the issue of the dead ends andstairs in each nger, walkways linkingthe ends of the ngers were introduced.

is greatly enhances the horizontalevacuation, allowing options for movinginto adjacent compartments from allareas of the KTC block. By providingthese additional options for horizontalegress, the number of stairs requiredcould be reduced.

By extending the logic of initialhorizontal evacuation, it becamepossible to provide a single stair in eachcompartment. ese were moved intothe voids and are fully open, designedto appear as accommodation stairs. eprotection to the stairs is provided bythe lines of compartmentation in thebuilding – occupants would not use

the stairs to evacuate the re-affectedcompartment; the stairs would only beused once occupants had already passedinto an adjacent, protected compartment.

Smoke control and glazing An additional benet to the removalof the compartment oors was that thevoid spaces between the ngers no longerbreach compartment oors. Underprescriptive code guidance, a void whichbreaches compartmentation is classiedas an atrium. As such, in addition to are-rated enclosure, it would be expectedto be provided with automatic smokecontrol, which would involve designingeither natural or mechanical extract atthe top of the atrium, and make-upair routes at the base, all of which

would need to automatically open or beactivated by smoke detectors.

By removing the compartment oors,

the need for smoke control was removed.is greatly simplied the design of

the roof and façade of these spaces. As the roof is constructed from ethylenetetrauoroethylene fabric, includingautomatic smoke control would haveinvolved additional openable elementsbeing incorporated into the design.

As the compartment lines run alongthe edge of the ngers, the design neededto ensure that re would not spreadacross the voids. e compartment walls

are therefore constructed from re-ratedmaterials, including re-rated glazingin the windows. e prescriptive coderecommendation is that this glazing

would be specied to provide bothintegrity and insulation from re.

By carrying out an analysis of theradiation from the window panels, it was

shown that the reduction in radiationfrom providing integrity-only glazing

would prevent re spread across thevoids by this mechanism. is resultedin a more cost-effective solution, withgreater exibility available for the designteam in the detailing of the glazing –see Figure 3.

Concourse spaceLinking the KTC block to the rest ofthe building is a large concourse space.

As this area is used as part of the egressroutes for the KTC, and is a key area ofthe building, it is provided with auto-matic smoke control. is is designedusing a re engineering approach, based

on agreed design re scenarios. eseare developed to allow exibility inthe use of the concourse base, whileensuring that re in this space wouldnot cause the evacuation of the adjacentcompartments.

e smoke control system is providedby coordinating the natural ventilationof the space at high level with theopenings required for smoke venting,and providing automatically openingmake-up air routes at low-level into

the space to ensure effective removal ofsmoke. is is shown in Figure 4.To assist the NHS foundation trust

with the implementation of the restrategy, typical examples of the levelof re loading that the smoke controlsystem is designed for were provided.

is was based on a collection of re

Figure 3: Glazing analysis for voids

The design needed to ensure that firewould not spread across the voids

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test data of information kiosks, furniture, display boards and

other relevant materials that could be encountered in theconcourse.

By adopting a re engineering approach to the designof the building, it was possible to allow open oors,increased natural light and greater exibility in the useof the spaces, along with a cost-effective solution both interms of capital cost and ongoing operational and maint-enance costs. For Arup, working closely with the design team,the trust and the approval authorities was essential throughoutthis process, to ensure that the design progressed withminimal risk and approval was granted on time. e resultis a unique healthcare facility, freed from the restrictions

of the prescriptive code guidance Andy Passingham is an associate director

with Arup Fire

Figure 4: Smoke control for large concourse space

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Hospital Fire Design - Article