The house stood out among its neighbors: not because of its box shape or the tall ham-radio tower planted in the parking space, but because of its bold two-tone exterior of wine red interrupted by sections of gray. The company that built it keeps costs down by not erecting model homes, so the salesman brought us to the recently finished building in central Chiba Prefecture, which was already occupied. The young couple were happy to show off their new purchase, and while the all-wood interior was the construction’s main selling point, it was the outside that made the biggest impression. Looking closer, we discovered it was corrugated metal.

“It’s called galvanium,” the salesman told us. It felt like plastic thanks to the coating, which he said was similar to the finish of an automobile, but it reminded us more of lacquer. He said it was inexpensive but long-lasting. Even the roof was made of galvanium. It would never rust, he explained, nor would it need re-coating.

It sounded too good to be true, and maybe it was. We later called a carpenter and asked him about galvanium — galvanized aluminum-zinc alloy used as siding, a surfacing material for outside walls — and he said it was “cost-effective, but cheap is cheap.”

Metal siding is becoming popular with Japanese builders who want to convey a stylish and practical approach to home design. It doesn’t look like the exteriors that people expect from mass-produced home builders and the houses that use it tend to feature facades that mimic Western housing traditions. Compound siding can resemble brick or stucco or wood.

The long-term result is often a house that looks older than it really is. We have been inspecting previously owned homes for years now and are usually disappointed before we even walk through the front door. Japanese homes start depreciating in value as soon as someone moves in, and no physical attribute reflects this economic reality more than a building’s exterior appearance. What’s significant about the increasing popularity of metal siding is that it was once very common, applied directly to the wood-and-mortar facades of traditional Japanese family homes rather than subjecting those facades to expensive, time-consuming refurbishment. The countryside is filled with what have become eyesores — older houses encased in dull, rust-stained metal.

Now, in an ironic turnaround, metal is a design statement. The owner wants the house to seem modern, or at least different, by avoiding siding that copies natural facades. Metal may not look natural, but it doesn’t look fake-natural either.

There are a number of reasons why natural exteriors are not common in Japan. Wood, which is still the standard in Europe and widespread if not necessarily dominant in North America, has always been problematic in Japan in terms of both cost and safety. Fire-prevention codes vary from region to region, but cities, in particular, tend to discourage wood facades because of housing density and the greater likelihood of fire spreading quickly. Tokyo used to be famous for burning down every dozen years or so — and then rebuilding just as quickly. It can even be said that the nature of Tokyo’s urban makeup, which seems to change completely every generation, has its roots in this historical cycle.

Nevertheless, workmanship in timber is highly advanced in Japan, as evidenced by all the temples and shrines that have lasted for centuries. The problem with houses is that space is required between the outer and inner walls to facilitate drying and thus prevent mold and rot, but some localities forbid openings behind wooden exteriors because, as one architect told us, “the thinking is that a flame won’t spread as easily along the outside of a building if it can’t consume the wood from both sides.”

The main strike against wood, however, seems to be economic. Wood is generally thought to be not resilient enough for exteriors, even though it is a standard facade material in other parts of the world. This prejudice may have less to do with the inherent properties of wood — Japanese cedar and cypress are considered by some architects to be ideal building materials — than with the fact that a wooden property requires the owner to take care of it. Because many homeowners are not conditioned to think their homes will outlast them, there’s no real incentive for upkeep except as last-minute cosmetic reform to help sell a property. In fact, any improvement that adds to the value of a house causes the property tax to go up, and that in turn becomes another disincentive.

Checking the pros and cons of different claddings

Ki (wood)
Merits: breathes, biodegradable, good appearance
Demerits: flammable, requires maintenance
Relative cost: higher

Tairu (tile)
Merits: durable, good appearance
Demerits: poor performance in earthquakes, requires maintenance
Relative cost: higher

Yōgyō (fiber-cement)
Merits: fire-resistant
Demerits: can fade and warp (depending on quality)
Relative cost: average

Nurikabe (mortar/stucco)
Merits: breathes
Demerits: requires maintenance, can crack
Relative cost: average

Kinzoku (metal)
Merits: lightweight, durable
Demerits: conducts heat, dents easily, poor acoustics
Relative cost: low

Wood also requires skilled labor, which is where using premeasured siding makes the biggest cost savings. Siding can be installed in less time than it takes to put up a timber facade. Consequently, the housing industry promotes siding, most of which is a variation on cement-and-fiber. Years of development have not only improved siding’s functionality — greater protection from pests and mold, less flammability, better temperature control — but also its cosmetic attributes. Salesmen will say that some siding products never need to be painted or treated, just cleaned every so often; but siding weathers all the same, which means less expensive kinds can warp and discolor (“cheap is cheap”). Also the caulking between the panels is not indestructible and will probably have to be replaced every 10 years, if not sooner. One type of siding called Powerboard, manufactured by Asahi Kasei for its related housing manufacturer Hebel Haus, is acknowledged as the most fire-resistant material for exteriors. Siding has become so common that nurikabe (mortar), once the norm for Japanese exteriors, is not offered any more, even as an option, by some housing companies. Probably the most expensive non-natural exterior method is tile, which is available in a variety of forms, from shiny ceramic to real brick facings and slabs of slate.

Another concern associated with the proliferation of siding is sustainability. Because Japanese homes aren’t necessarily expected to last more than 30 or 40 years, disposal is a problem, and local governments are trying to come up with solutions since some refuse processors do not accept certain types of housing materials. Newer types of siding are designed to be recycled, but some siding are made of materials that are not even suitable for landfill.

As with all issues related to housing in Japan, the basic determinant is land price. In order to afford their little parcels of dirt, homeowners cut corners on the structures, and the exterior is an area where people seem most willing to compromise. For a reasonably priced home, selling for around ¥15 million, the standard cost of the exterior will be about ¥2 million. A buyer with a limited budget who is also averse to conventional siding may wonder if spending another million or two for wood or mortar is worth it. To that person, galvanium may not look so bad — at least for the time being.

Philip Brasor and Masako Tsubuku blog about Japanese housing at www.catforehead.wordpress.com.

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