the Carpentry Way: Enter the Octagon (III)                                                          

Enter the Octagon (III)


In the foregoing post in this series, I looked at Orson Squire Fowler's work in the mid-1800s to popularize Octagonal houses. I spent some time demonstrating the inherent efficiency, when measuring the amount of floor space achieved for a given amount of liner feet of wall, of the octagon over the square and rectangular plans. Personally, I found this basic number-crunch quite eye-opening, as it has shifted my ideas about the forms houses might - or ought to - take.

Personally, I've always tended to like rectangular houses,  particularly ones with ells, wings, u-shapes, stepped patterns, etc. I find them visually interesting for one thing. I like Japanese houses with staggered patterns, what they term the 'goose-formation' pattern, along with New England connected farm buildings of a similar configuration, a pattern here christened the 'big house little house back house barn' pattern. Now those forms of buildings, historically speaking, evolved over time. People needed more space, or didn't see the sense in cold weather in having to walk outside of the house to get to another building, so they added on to one building with another, in a graduated fashion, as budget permitted. When you're adding on to space, it is much easier to tack one building on to another, make a hole through the adjoined walls to connect the spaces and stitch the colliding roofs up in some way - something not always especially elegantly done from what I have seen. This is the more obvious approach to adding space, as one doesn't have to open up the roof on the existing house and modifications to both structures are minimal.

In Japan, the sense of architectural space is such that there is a definite preference for spaces in which one 'discovers' new views and scenes by turning the corner, each room connected to another and yet potentially very different in feel or theme. Like pearls on a string. Or like stations on a subway line -  the dark route between individual stations is not so critical, it is the stations themselves that are the interesting part.

It is one thing when building have evolved over time into forms like that, and it is quite another to construct them from new in such a pattern. There's more than a little of that going on around here - near where I live there are entire subdivisions of new houses with attached pseudo back-houses and pseudo-barns. Not a lot of small-holder farming going on there I suspect. Fowler decried especially buildings constructed on patterns of jogs or wings, as these manifest all the faults of long rectangular buildings (i.e., a lot of wall for very little enclosed floor space), but even to a greater degree.

Consider the following situation in which you place together two floor areas, one main space at 30' x 45', and the other, a 'back house' at 24' x12':

This is a fairly common pattern in New England, the back house being the new kitchen, and invariably later added onto until the overall plan becomes 'T'-form'. Note the portions of the inward jogs, where I have labeled the walls as 'a', 'b', 'c', and 'd'.  Adding up our square footage, we have (30 x 45) + (12 x 24), a total of 1638 square feet, and we needed 174' of wall to accomplish that.

Now, keeping in mind those labeled wall sections,  'a', 'b', 'c', and 'd', we could alter the configuration, and not add one single bit of extra wall, by moving them as follows:

I left dotted lines in the drawing to show the original plan. We now have a plan that is getting closer to a square in overall configuration. We have also eliminated a fair amount of cutting work, if you consider the three corners required at each end to accommodate the inward jogs have now been replaced by a single corner. Square footage in this plan is 45 x 42 = 1890, a 15% increase. Wall length is identical.

So building from new in a plan with jogs, ells, and wings, makes less sense economically in terms of outlay for materials and amount of cutting required. In a warm climate, I would say that long stretched out buildings of a single floor make sense if the goal is to maximize ventilation and catch breezes. In a hot climate, nobody is going to want a bedroom on an upper floor under the roof. A long stretched out house, as it has more wall area in relation to floor area, allows for a greater number of wall openings to allow that breeze in and through.  A skinny stretched-out house makes sense for such a climate.

In a cold climate, more external surface area only adds to the heating bill. It makes much better sense in a cold climate to have a condensed floor plan, in the form of a short rectangle, a square, or a polygon, and to have more than one floor, so that the heating of the first floor can contribute toward the heating of the upper floors simply on the basis of warm air rising. Wall penetrations should be minimized in such a house, especially on the northern side of the structure, or on sides regularly exposed to cold winds.

An octagonal house, in terms of how it faces the wind, is much less of a block than a rectilinear house:

Also, in terms of the structure resisting the racking effects on the frame that come from the wind pushing against a wall, consider that the square/rectangular timber framed house would employ diagonal horizontal braces at the interior corners, whereas with an octagonal house and entire wall is oriented on a 45˚ making it stable, on the basic of the geometry to the same loads. It's like the advantage of a hip roof over a gable roof in terms of the inherent triangulation gained.

Fowler felt that a 3-story octagon house was ideal in such a climate, as the bedrooms could be placed on the second floor so as to be in that happy medium between too cold and too hot. Having slept in houses on the top floor under the roof here in New England, I can attest to the fact that such spaces are not conducive to getting much sleep in the heat of summer.

There are a few websites out there which catalog the many octagonal houses in North America. I've looked at dozens of examples, along with those put forth in Fowler's book, and frankly I don't tend to find many of them especially attractive in terms of their appearance from the street. Part of that response might be simply due to the novelty of the structural form, and now that I see and better understand the virtues of the form I am beginning to view the octagonal house more favorably. I think the least attractive portion of these houses, coming from my perspective as admirer of Japanese traditional vernacular architecture, is that the roof doesn't look quite right most of he time. I especially dislike the commonly fitted central cupola, which to my eyes looks an awful lot like a lighthouse:

The above example is the Hyde Octagon in Mumford New York.

Another famous example of an spectacularly large octagonal house is in Natchez:

I really find the domes and central towers a bit much in these designs. For some reason I like towers on the perimeter of a structure, not so much in the middle.

But, mostly it is the roofs overall I don't care for, with one exception. The roof that suits this form, I do believe, is the mansard:

Here's another example from Massachusetts - remove that cupola on top and it would be even sweeter:

I was surprised to find, upon a little digging around, that there are companies in Japan touting the virtues of the octagonal house plan. Here's an example of a newer Japanese house built on an octagonal plan:

Nothing especially exciting about that house, in my view.

Octagonal structures do have a fairly long history in Japan, associated to Buddhism  - perhaps because of the 'eight-fold- path that forms a central tenet in most schools of Buddhism. Here's a few examples of octagonal temple structures, starting with one of the most famous, the Yumedono at Hōryū-ji (法隆寺) in Nara:


This one is Buddhist in origin, though located within the precincts of a shrine on Enoshima, an island in Sagami Bay:

Another example - hope this prolonged set of examples isn't too boring:


This one has an intriguing upper roof:


Let's not forget China:

Now, I happen to be one of those people who thinks that temples do not make good archetypes for building residential architecture, but I like looking at those buildings all the same.

A lot of people wonder what the interior arrangement of an octagonal house would be like, and what advantages, if any, such a plan confers. In Fowler's book, a number of different floor plans are proffered and explained in detail. Here's one:

And another:

In fact, if you do an online search for 'octagonal floor plan', you'll find hundreds of examples with much variety in approaches to layout. There are as many ways to slice up the pie, as it were, as with any rectangular/square house's floor plan.

One Japanese site advocating for octagonal homes had some great graphics which I have shamelessly pilfered. Hopefully by providing a link they won't sue me!

Comparing an office or study room in an octagonal house with a room in house with 90˚ corners, same square footage in each, we can see the following:

In the square-cornered room, much of the space at the corner is poorly usable, access to one of the bookcases is constrained, and if a view is desired, much of it is obscured:

In the octagonal house room, there is much more desk space, more room for the bookcases, and a more panoramic view could be had with additional windows:

Seems like a better place to hang out - the guy seems pleased. Yay!

Fowler also mentions the dead space one obtains with the interior 90˚ corners in buildings. He argues that the octagon's interior partitioning would allow for nearly every room to have a triangular closet, which he states are more accessible and useful spaces than one gets with rectilinear closets, which of course have those same dead spaces in their interior corners. He further lays out the benefits of a more condensed centralized plan, as it shortens the distance between places in a house making it less tiring to get from one place to another.

I think all in all that Fowler's An Octagon House for All has much of value to contribute to how we think about designing houses. Whenever we build, we need to think of site first. An octagon house can be placed extremely well on a variety of lot shapes, even triangles which are quite awkward places in which to put a rectangular or square house. Site also relates to prevailing winds and solar orientation. An octagon house would tend to present a flat wall surface to several positions as the sun arcs across the sky, making it a good choice for passive solar. The octagon house lets the wind pass by more easily than a house with square corners. Then we can think of building for time-  is an octagonal house easily modifiable, can it be added on to? Absolutely. And then, we can consider the usual matters of cost and square footage, where an octagon house is clearly superior in terms of efficiency of material use.

All that said, I have to express a certain amount of apprehension at the idea of framing a building with 45˚/135˚ turns, and 22.5˚/67.5˚ miters to deal with. While it isn't challenging carpentry particularly, after working on a deck for a local carpentry company a month or so back, I noticed that the previous carpenter had managed to configure the octagonal portion of the deck with a 41˚-49˚-49˚-41˚ bump out (that's one of the reasons why he was fired I guess), so maybe octagonal buildings are asking for trouble? Even square and plumb seems to be more and more of a rarity these days, so finding carpenters to frame, say, a roof on an octagonal house might be hitting 'tilt'? I hope not. It's not that bad is it?

My take on the octagon house is that it is a very good shape to build with, but it doesn't mean that from here on out it is give me octagons or give me death - look out Chuck Norris!. It means that when considering the matrix of site, climate, budget, and value for money, I now have a new lens to click into place. Octagonal houses make sense in a lot of cases, and I would now tend to argue against long skinny houses in colder climates. I thank Orson Fowler for opening my eyes to that.