Building Heritage

Whenever the issue of heritage buildings comes up, my natural scepticism comes to the fore. In Wellington I was involved in a number of very dubious “heritage” buildings whose aesthetic and historical merits were at best murky. For me, the issue was best summed up by Ed Byrne when he complained about being forbidden to smoke onstage in Australia because of a “heritage” carpet. “I’ve played in pubs older than your country, and they let me smoke in there!” It always seemed to me that these well-meaning efforts to preserve the “character” in, say, Cuba street, were more aspirational than merited, and in the process were creating a substantial life hazard. In fact, there’s a paradox in it: forbidden to make the changes to a building that would preserve it in an earthquake in the name of preserving its character. You can’t win.

When I look at buildings whose preservation does seem merited, one common feature emerges: those buildings are still viable structures. The best example to my mind is the old Government House on Bowen Street. It was extensively preserved and restored, and fulfils a valuable role as the Law School for Victoria University. As a relatively lightweight timber structure, it was adaptable but reliable, and the necessary seismic strengthening for modern standards were both massive and intrusive but did not affect the basic character of the place. It’s a viable building. The very unsound construction of most of Cuba Street puts those buildings in a different category: however sentimental you feel about them, they’re just no earthly use and need to go.

The situation in the UK is not intrinsically different, but the risks are lower due to the lack of seismicity. Iconic and important buildings require a level of detailed care that can sometimes stagger belief. And yet, colleagues are still reporting the same kind of myopia and disconnection from the fundamental purpose of a building. One colleague was prevented from replacing a marginally-adequate timber floor with something appropriate because of heritage tiling. Instead, the proposal is to build a new floor over the top of these tiles, burying them. The floor can’t be made viable without disturbing a historical construction that’s contributing to the problem of viability! Just what is the point of this strategy? Who benefits? Nobody will ever be able to use this “preserved” floor. I think, on the whole, “facade retention” seems to be the best compromise position for most “historical” buildings.

A more interesting aspect of the problem that has been occurring in our flagship projects, particularly in Oxford, is previewing future heritage value. At the moment, my team is involved with three buildings that are in, amongst, and around existing Grade 1 listed Historical Buildings that are multiple hundreds of years old. In that context, talking about your standard “50-year” design life is nonsensical, and even the nominal “100-year” design life may be under-playing the real in-service lifespan of some of these buildings. This raises a lot of technical questions: how long will the reinforcing inside the concrete last? What is the extra-super-long-term deflection profile of the building? How durable is the aesthetic of this building? In particular, I worry that the modern glass-sheathed building won’t age well – only time will tell.

When we think about the long-term life of a building, it’s unlikely that we’re thinking about a long-term stasis of use and occupation. Any structural engineer who’s been around for a while will have been involved in a whole-building overall where an existing shell, or maybe just certain key parts, have been retained while the majority of the building is replaced. Anecdotally this is more common in residential buildings than commercial buildings, but over a long-enough timespan there are few buildings that aren’t overhauled. The danger alluded to above, of Heritage-imposed stasis, spells a slow and lingering death for buildings that could experience renewal but whose existing fabrics are unsuited for their historic uses.

Stewart Brand’s study in building alterations, How Buildings Learn, can provide a lot more detail on the topic if you’re interested. I’d just like to highlight a couple of key conclusions. All things being equal, Steel structures are actually the most robust, updatable and adaptable while concrete, particularly post-tensioned concrete, can be quite a challenge to meaningfully alter. From the super-long-term point of view, structures perform better the more redundancy they have built-in. Your garden variety steel portal frame building has an almost unbeatable level of redundancy, and can be drastically altered reasonably easily. Timber-framed houses outside of seismic zones too. Elegant stone archways on the other extreme, can seldom be altered in any significant way.

Robust designs are good for the long-term, but in the short term they are often more expensive or more difficult to fit into architectural constraints. Generally speaking, “good architecture” means “non-rectilinear” or even “irregular geometry” and “thinnest possible elements” and “fewest possible walls”. I recently saw a preliminary design for a new industrial lab complex designed with post-tensioned reinforced concrete floors, a minimum number of structural columns, no walls, and cantilevers around the building perimeter. For a building intended to be a working lab complex whose future equipment is purely hypothetical, such a design is a potentially catastrophic straight-jacket. As soon as they need a new hole through a floor, they’ll be compromising the basic structural premise of the floor system. I suspect that’s one building complex that will never get to be Heritage because in 50 years when different technologies are in vogue they’ll have to tear it down and build whatever they think they need at that point in time instead.

In some ways this conversation is already too late for some architects and developers. I was recently involved in fitting out an empty shell for a company, and the first thing they did was cut holes in between the floors of the building for feature stairs – no big deal in a steel-beam building because you just trim around the opening with more steel and everything’s fine. The developer for that building told me that they would only be building post-tensioned RC from now on, removing the capacity for such tenant-driven alterations and potentially meaning that the building would now be an empty post-tensioned RC building instead of an occupied steel frame building. Steel is out, concrete is in, and I’m not entirely sure why.

Having a Heritage framework can also created some interesting economic anomalies. In The Death and Life of Great American Cities, Jane Jacobs argues that for a healthy city economy, you need a mix of new and old building stock. Her idea is that old building stock have lower rents, allowing start-up companies to afford premises. However, conceptually, a Heritage Building retains its new-building value, because its age becomes a selling point rather than a drawback. Often the maintenance and running costs of Heritage buildings are higher than modern buildings, and the basic amenities are poorer. Compounding this is that most Heritage buildings about which a central authority might care are in “good” areas of town. Nobody is quite as interested in old buildings in scummy warehouse districts as they would be in the same building on a city’s main streets.

In Wellington, in particular, quite a few buildings in the “character areas”, particularly Cuba Street, are facing huge seismic strengthening costs because they’re made from brick or poor-quality concrete. For these buildings, the owners face the prospect of having to implement strengthening that will significantly affect the useable areas of their buildings, but can’t affect its aesthetics, and gain none of the benefits you get from a new building. It’s the worst of all possible worlds, where an old building is already costing more based on its age and is about to cost a huge amount to upgrade, and you get no day-to-day benefit in any way. It’s not too surprising that half way through the 15 year initial time-limit for seismic strengthening when the legislation changed in 2006, comparatively few buildings have received anything like adequate structural attention. There was a suggestion of pushing out the seismic strengthening timeframe to 25 years, in which case we might as well just admit it’s not going to happen. What really needs to happen is genuine renewal – let those buildings be demolished and buildings of an appropriate high-calibre status be built. But when they’re built, make sure they’ve an eye to the future so genuinely viable future-Heritage buildings can go in this “character” area.

Historically, I think we can point to some pretty good evidence that buildings that deserve to survive generally will. We have buildings that survived from antiquity not because there was some multi-millennium “Heritage Watchdog” actively preserving these buildings, but because their uses were adapted on an ongoing basis for the use of living people. They no longer needed a Temple to Zeus, they needed a temple to the Christian god. The building doesn’t care – it just knows its roof is getting replaced, and its stone mortar is getting renewed. Of course some quite good buildings will be lost, but in the scheme of things, does that matter? If what replaces them isn’t better, it’s going to suffer the same fate.

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