Contrary to common wisdom, Japan's traditional wooden buildings are remarkably sustainable -- a fact that has tended to be obscured by the rapid economic growth and urbanization of Japan in the latter half of the 20th century. In this lecture, I will discuss how I came to reaffirm the sustainability of traditional Japanese wooden buildings through my research of construction methods and my practice as an architect. My main focus will be on durability, because a building will not be sustainable if its materials and structures degrade relatively fast, however beautiful and functional it may be from the viewpoint of architectural design. Flexibility in long-lasting buildings - assuring an extended lifespan Foreigners visiting traditional Japanese wooden buildings for the first time are often fascinated by fusuma, sliding partitions that can be effortlessly opened and closed to instantly alter room configurations to suit the occasion. While movable office partitions are not uncommon in western cultures where load-bearing walls are the norm, the traditional Japanese device of fusuma probably appears magical because it completely alters the space without leaving any marks on walls or posts. Many of the lesser posts are also movable, and even a whole building can be disassembled, moved, and put together again at a different location. In extreme cases, a standing house can be dragged in its entirety to a different place. This remarkable flexibility is precisely what makes traditional Japanese wooden buildings so long- lasting. It is also what makes them mysterious to those who are only familiar with stone buildings and load-bearing walls. (Fig. 1) Easy to renovate and expand - the art of flexibility inherent in traditional Japanese wooden buildings Why are these traditional wooden buildings so easy to renovate and expand? The answer lies in the post-and-beam structure, which fundamentally differs from the load-bearing wall structures used in western architecture and found in brick and block buildings, log houses, and reinforced concrete buildings. The posts can be relatively thin, and they can accommodate sliding partitions (such as fusuma and shoji) in a configuration known as shinkabe- zukuri, which leaves the posts exposed. Even with this method, however, the freedom to renovate and expand has its limits: the design has to be based on units of about 3 shaku (1 shaku = 30.3 cm), and each room has to contain either 4.5, 6, 8, or 10 tatami modules (1 tatami module = 3 x 6 shaku). (Fig. 2) The tatami module is also a unit of spatial perception shared by all Japanese. In fact, it is by this Figure 1.The Osaka Museum of Housing and Living（drawn by Hozumi Kazuo） Sustainable buildings and life Summary of Lecture by Dr. Yositika Utida Figure 2.The explanatory drawing of SAR（N.J.Habraken）
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Contrary to common wisdom, Japan'stradit ional wooden bui ld ings are remarkablysustainable--afactthathastendedtobeobscuredby the rapideconomicgrowthandurbanizationofJapan in the latterhalfof the20thcentury. In thislecture, Iwill discusshow I came to reaffirm thesustainabilityoftraditionalJapanesewoodenbuildingsthroughmyresearchofconstructionmethodsandmypracticeasanarchitect.Mymainfocuswillbeondurability,becauseabuildingwillnotbesustainableifitsmaterialsandstructuresdegraderelativelyfast,howeverbeautifulandfunctional itmaybefromtheviewpointofarchitecturaldesign.
Flexibility in long-lasting buildings -assuring an extended lifespan Foreigners visiting traditional Japanesewooden buildings for the first time are oftenfascinatedbyfusuma,slidingpartitionsthatcanbeeffortlesslyopenedandclosedtoinstantlyalterroomconfigurations tosuit theoccasion.Whilemovableoffice partitions are not uncommon in westerncultureswhere load-bearingwallsarethenorm, thetraditional Japanese device of fusumaprobablyappearsmagical because it completely alters thespacewithout leavinganymarksonwallsorposts.Manyofthelesserpostsarealsomovable,andevenawholebuildingcanbedisassembled,moved,andputtogetheragainatadifferentlocation. Inextremecases,astandinghousecanbedraggedinitsentiretytoadifferentplace. This remarkable flexibility ispreciselywhatmakestraditionalJapanesewoodenbuildingssolong-lasting. It is alsowhatmakes themmysterious tothosewhoareonlyfamiliarwithstonebuildingsandload-bearingwalls.(Fig.1)
Easy to renovate and expand -the art of flexibility inherent in traditional Japanese wooden buildings Whyare thesetraditionalwoodenbuildings
soeasytorenovateandexpand?Theanswer lies inthepost-and-beamstructure,which fundamentallydiffers from the load-bearingwall structuresusedin western architecture and found in brick andblockbuildings, loghouses,andreinforcedconcretebuildings.Thepostscanberelatively thin,andtheycanaccommodateslidingpartitions(suchasfusumaand shoji) in a configuration knownas shinkabe-zukuri,whichleavesthepostsexposed. Evenwiththismethod,however,thefreedomtorenovateandexpandhasitslimits:thedesignhastobebasedonunitsofabout3shaku (1shaku=30.3cm),andeachroomhastocontaineither4.5,6,8,or10tatamimodules(1tatamimodule=3x6shaku).(Fig.2) The tatamimodule isalsoaunitofspatialperceptionsharedbyallJapanese.Infact,itisbythis
Figure 1.The Osaka Museum of Housing and Living（drawn by Hozumi
Kazuo）
Sustainable buildings and lifeSummary of Lecture by Dr. Yositika Utida
Figure 2.The explanatory drawing of SAR（N.J.Habraken）
measurethatwementallypicturethesizesofindoorspacesalongwith theactivities that takeplace inthem.(Fig.3) On topof thecubicspacedefinedby theshinkabestructurecomestheroofstructureknownaswagoya,whichisalsoaveryflexiblesystem,unlikethetrussedroofsused inwesterndesigns.Withthewagoyaroof,strutsarebuiltatopthebeams;moya(purlins)are fixedhorizontallyacross thesebeams,withtaruki(rafters) laidontop,formingtheslopeoftheroof.Thissimplesystemensuresthatthestrutsandpurlinssnuglymatchthe3-shakugrid,allowingroofs tobebuilteasilyonanyplanthatshares thesamegrid.Hippedroofsbuiltonthissystemcanshedrainwaterextremelywell,nomatterhowcomplextheexteriorformofthebuilding.(Fig.4)
The design quality of traditional wooden buildings - free yet orderly With the wagoya system, hipped roofscanbe constructedwith surprisingly few specialcomponents,andmostofthepartscanbereusedinrenovation.Thereisalsoconsiderablefreedominroofdesign.Using irimoya-zukuri (thehip-and-gableroof
Figure 3.The basic spaces of NOH（Konbaru Kunio）
Figure 4.The generality of hipped roofs（drawn by Iizuka Gorozou）
Figure 5.The components of a building- from the foundation to the
roofs -
Thecombinationofwagoyaandshinkabestructuresallowsahighdegreeof freedom in thedesignof thesebuildings,as itensures thatallofthespacedefinedbythestructuralcomponentsofabuilding-fromthefoundationtotheroofs-usestatamimodulesasitsbasis.(Fig.5)
Katsura Rikyu -a classic example of flexible architectural design TheKatsuraRikyu(KatsuraDetachedPalace)is anexemplarybuilding that combines shinkabe-zukuriwithwagoyaroofs.(Fig.6) When this imperial villa underwentmajorrepairs in 1982, itwasdiscovered that the chu-shoinwinghadbeenexpandedaround1620-40.Theexpansionprocess involved, amongother things,removingapostfromanexistingroomandmovingthewallswithoutleavingatraceofthealteration.(Fig.7-8)
NEXT21 -a sustainable Japanese building of today Built byOsakaGas in1993,NEXT21 is apilothousingcomplexwhereexperimentsarebeingconducted tocreatesustainableurbanhousingforthe21stcentury.(Figs.9,10) Structuralcomponentshavetobereplacedfrom time to time in long-lasting residences, andto facilitate this process a concept ofmodularcoord ina t ion (MC) , i . e . , s tandard i za t ion o fcomponents,was adopted in the constructionofNEXT21.DecisionsonthestandardswerebasedonstudiesoftraditionalJapanesewoodenbuildings. The expected lifespanof each structuralcomponentisasfollows:-Skeleton(posts,beams,floorslabs):50-100years-Cladding(outerwalls):25-50years-Openings(doors,windows):25-50years-Infill(interiorfloors,walls,ceilings):12-25years-Facilities(pipes,wiring,equipment):6-12years Since1993,NEXT21has undergone twointerior renovations, andmodifications to the
Figure 6.Katsura Rikyu：measured and drawn by Nishizawa Fumitaka
Figure 7.The restoration：Katsura Rikyu in about 1620（drawn by Saito
Hidetoshi）
Figure 8.The restoration：Katsura Rikyu in about 1640（drawn by Saito
Hidetoshi） Figure 10.The components of the NEXT21
Figure 9.The exterior of the NEXT21
balconies and outerwalls have also beenmade,provingtheflexibilityofitsdesign.(Fig.11)
Modular coordination supports the durability of social infrastructures TheMCconcept implementedatNEXT21 isasuccessor to theCenturyHousingSystem(CHS)concept developed in 1983, and is designed forapplicationintallerbuildingswithreinforcedconcretepost-and-beamstructures.Thepostsusedarethickerthan those in conventional buildings, andbroad,windingmulti-levelcorridorscalled rittaigairo (3Dpromenades)connect theresidences.Themodulescome in three sizes (large,medium, and small),and the flexibilityof thestructure that integratesthesemodules hasbeenwell proven through20yearsofexperimentsatNEXT21.That istosay, thesustainabilityofthisbuildingasasocialinfrastructurehasbeenclearlyestablished.
History and current state of MC studies TheMCconceptmayseemreminiscentofModulor, an anthropometric scaleofproportionsdevisedbyLeCorbusier.ButwhereasModulor isbasically a systemof proportions based on thegoldenratioandmeasurementsofthehumanbody,Japanese-bornMCisasystemofintegrationinspiredby the flexibility of traditional Japanesewoodenstructureswiththeir tatamimodules.Therefore, themainconcernofMC istherelationshipbetweenthegridsof abuildingand the sizesof its structuralcomponents. Whenconstructionof the firstgenerationofhigh-risesbeganinJapan,astandardmodulesizeof80x80cmwasadopted,becausethesprinklers(by far themost costly component at the time)requiredagridof3.20x3.20meters.Lookingbackon thehistoryof therelationshipbetweenthegridandcomponentsizes,wecancertainlysaythat theMCsystemoftenextended the lifespanof socialinfrastructures, but the system is also inevitablyaffectedbychangingsocialneeds.Andsincewearestrivingtorealizeasustainablesociety,wemustmakesure theMCsystemevolves in the rightdirection.Agoodexample is theNewMarunouchiBuildingcompleted in2007,whichrevivedtheoncepopular90x90cmmodule.Theadvancedresearchbeingcarriedouton theMCsystem in Japanwill surely
Figure 11.The moving experimentation of outer walls
Changing trends affect the physical life of a building Needlesstosay, therearephysical limitstohow longwoodenbuildingscan last. Interestingly,however, although relatively fewwoodenbuildingsdatingfromtheHeianPeriod (late8th to late12thcentury)survivetoday,thosefromtheprecedingNaraPeriod (8thcentury)andthesucceedingKamakuraPeriod (late12th toearly14thcentury)aremorenumerous.The reasonwhymanystructures fromtheNaraPeriodstill remain is that theirpillarsarethickerandtheirnageshi(non-penetratingtiebeams)aremore robust than theirHeiancounterparts. IntheKamakuraPeriod,woodenbuildings regainedsturdinesswith the introductionofChinesenuki(penetratingtiebeams)byChogen,whowasinchargeofcontemporarynationalconstructionprojects. IntheEdoPeriod(17thtomid19thcentury),whenthenow-familiarsystemof traditionalwoodenhousingwasestablished,buildingsbecame lesssturdyagain,duetotheuseofthinnerpostsandbeamsaswellasweakershiguchi (angle joints).Whileshiguchiwerereinforcedwithmetal in theMeijiPeriod (late19thtoearly20thcentury), deteriorationof themetalcomponentsledtoreducedsustainability. Thelifespanofwoodenbuildingsthusseemstohavebecomeshorterasthecenturieshavegoneby.Likewise,sincethe late19thcentury, theusefullifeofbuildingsappears tohavebeenaffectedbyindustrialization,asthe introductionofuntestednewmaterialsandnewtechnologiesdictatedthephysicallifespanofbuildings. Thepropertiesof concreteand steel havebeen scrupulously examined fromthematerial, technologicalandstructuralviewpoints,precisely because the experts have hadmajorconcernsandmisgivingsaboutthesematerials that
havecometopredominateinmodernbuildings. ImyselfwitnessedaperturbingexampleattheTsushimaTelephoneOfficebuilding, inwhichtheearlierbuiltsectionsturnedouttobe lesspronetosoilingandstainingthanthelateradditions. When Gustav Eiffel designed the EiffelTower (1889) as a forerunner ofmodern iron-basedstructures,hedidnotusesteel,whichwasjustemergingat thetime,butadoptedtime-provenwrought iron instead.Asanengineeranddesigner,Eiffel certainly believed in the potential of newmaterials andnew technologies, but at the sametimehehad tobepractical and responsible as acontractor.(Fig.14) At the time, views on the relationshipbetweenarchitecturaldesign,materialsandstructuresdifferedgreatlyfromplacetoplace.TaketheChurchofNotre-DameduRaincy(1923,AugustePerret)andtheStockholmCityHall (1923,RagnarÖstberg), forexample.WhenIvisitedtheformerin1980,workwasunderwaytorepairalltheflaked-offconcreteandtopreventthestructurefromcollapse,whilethe latter,
madeofbricksandstone,stoodfully intact inall itsstatelybeauty.(Fig.15,16,17) Concerns and m isg i v ings about thesuitabi l ity of new construction materials andstructurespersisted,andtheybecamethesubjectofrigorousscientificandtechnologicalstudies.Thesestudiesprovedtheworthinessof thematerials,butunfortunately,R&Dresultsdonotalwaysmatchwhatpeopleare lookingfor inarchitecturaldesign.Whensuchmismatchesoccur,buildingscannotattain thedesireddurability. Ever s ince the Industr ia l Revo lut ion ,technologicalinnovationshavedrivenindustrialization.Asproductionsystemsbecome increasingly largerin scale andmore complex, however, industrialorganizations also becomemore diverse andcompartmentalized. Thepurposeof constructionengineering is to integrate diverse architecturalknowledge and reconcile itwith practical designrequirements. In this field of study, one has tobecareful not to takeestablishedknowledge forgranted,becausesomeof theunderlyingpremisesofa technologymayberelativelyshort-lived,whileothersmaypersistmuchlonger. Also, I have learned fromexperience thatit takesavery longtimebeforeasetofmodules isrecognizedasastandard.
Towards attaining sustainable buildings Socialchange isexpected toslowdown inthecomingageofsustainability.Toconstruct trulysustainable buildings,we need to fundamentallyrevisethewayconstructionengineersapproachtheirproblems.Ihavetwopiecesofadviceforthem:
- In order to construct buildings thatwill last acentury,studythosethathavelastedthatlong.- Inorder toconstructbuildings thatwill last twocenturies,studythosethathavelastedthatlong. Modernbuildingengineershave reliedontechnologicalbreakthroughs to tamenatureonceandforall.Butsuchanapproachcanonlygosofar,andthe limitsarebeingreachedaswespeak.Justaswildanimalsareconstantly standingup to thechallengesofnature,humanbeingsshouldalsotakeamorearduouspath to secure sustainable livingenvironments.(SummarybyDr.SeijiSawada)
