Japanese House Building Query

[StevieB]

Currently very limited time to get into the workshop, but I do watch the odd YouTube channel to see others doing it! One I dip in and out of I think has been mentioned here before - Shoyan Japanese Carpenter. Clearly very talented but does use modern tools as well as traditional joints (and unexpectedly to me, a lot of screws!). Having just watched the compilation video of his latest house build:

https://www.youtube.com/watch?v=-okhGGeOYs4

I am struck by how tight together many if the pieces of timber are. He stands on some to get them to fit, and hammers others. We get very concerned by expansion gaps and wood movement over here, but it does not seem to be an issue in Japan and I wondered if anyone could explain why? Seasonal temperature fluctuations are clearly high so is the wood so stable that movement does not occur? Is everything so tight movement cannot occur (unlikely given when I was laying my parquet floor there were dire warnings of wood expanding and pushing out brick walls from relatively small parquet blocks) or does the whole building flex such that movement occurs but is not noticeable?

 

[Windows]

Things to consider:

1. Wood used for Japanese houses is typically softwood so different parts can compress to account for expansion in others.

2. Expansion gaps are found where a wood component is surrounded by other components that cannot move or compress, or when the expanding component itself is not itself compressible. For example, hardwood panels within a frame often get an expansion gap. Japanese construction has to deal with the same issues, but you may not see it discussed much when the focus is the framing rather than the stuff that fits within the framing.

3. Western house construction has more inflexible materials like brick than traditional Japanese wood frame houses, so the brick-wood junction is another area where you’d hear about expansion gaps in a modern western construction video, but might not hear about it in a Japanese construction video. Apart from just a difference in building style, there is a pretty significant difference in the geography/geology of Japan (earthquakes) and UK (no earthquakes) that explains some of the difference.

In short, wood expands & contracts the world over, Japanese wood frame construction has to take this into account, building materials in traditional Japanese construction favour flexibility in a way that is not seen in UK construction because of earthquakes, videos that focus on framing don’t always discuss expansion/contraction, but it is still being accounted for in the design.

You might like this channel too:
https://youtube.com/@thecarpentrylife

 

[Windows]

And I think the answer to your specific question is that the whole building flexes.

 

[Woodbloke]

And I think the answer to your specific question is that the whole building flexes.

Yep, they do, especially temples and shrines which are built to be earthquake proof. This is me outside a tall pagoda building at the Nachi Falls in Japan:



When you get up close and personal to the roof, having climbed the four sets of stairs, the roof construction is evident:



There are no 'joints' as we know them, but a series of complex, interlocking sections that are designed to move in the event of an earthquake, which is the reason that many ancient wooden structures are still standing.

They are not, however fire proof and many have been rebuilt several times over the centuries as they've burnt to the ground - Rob

 

[StevieB]

Thanks - that is helpful. Yes, I am subscribed to that channel as well - quite informative but well beyond my skill level!

 

[AJB Temple]

Fully nailed by Rob

The wood used is almost invariably hinoki (Japanese Cyrpus) which is strong and lovely to work.

You do see gaps, but they are factored into the design (much like shadow gaps in some western joinery and panelling).

There are some excellent books around on Japanese joinery and practical use of Japanese tools and methods.