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Green Building Bible, Fourth Edition
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General: Building in Japan 1

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  1.  
    • CommentAuthorRex
    • CommentTimeMay 28th 2025 edited
     
    What ho one and all,

    Have recently returned from a regular visit to Japan. While wandering around residential areas, I am always amazed at the quality of construction. Virtually all houses are timber frame, mainly of course, because bricks and earthquakes are not a happy mix!

    When I had my house built, the poured foundations, most likely, tick the structure box, but they did look rough around the edges. In Japan, the foundations have virtually polished shuttering and the result, even though it is never seen, is flat and perfect. Quite amazing to see; and I can only assume that the rest of the construction follows a similar high standard.

    All the timber is amazing; most is machined off-site but all fits together perfectly. None of the 'butt-joint and nail' that we get in the UK; everything is property jointed. The sole plates have pre-drilled holes that align with the foundation installed bolts.

    Looking at any site seems that the builders actually care about what they are doing. Everything is clean and tidy with no excessive mess left laying around.

    It is amazing.
      IMG_20250427_114052_343 (Small).jpg
    • CommentAuthorRex
    • CommentTimeMay 28th 2025
     
    Have never managed to find how to post multiple image to a post so will have to 'reply' to my own post!
      IMG_20250427_114101_649 (Small).jpg
    • CommentAuthorRex
    • CommentTimeMay 28th 2025
     
    Timber fixings
      IMG_20250427_114241_892 (Small).jpg
    •  
      CommentAuthordjh
    • CommentTimeMay 28th 2025
     
    What about airtightness and insulation?
    • CommentAuthorowlman
    • CommentTimeMay 28th 2025
     
    Stud and joist spacing is interesting, I'm guessing M&T between the two.
    All the specialist hardware is readily available over here as is Glulam. As are specialist tools, problem is, no one wants to pay. Plus all the other stuff associated with timber frame, mortgage, insurance etc etc.
    As well as earthquake, I guess climate has a lot to do with the differences, UK/Japan.
    • CommentAuthorRex
    • CommentTimeMay 28th 2025
     
    Climate may be an issue but they not only get a long(ish) rainy season but there are times when the humidity is a nightmare. On the other hand, winters around the Tokyo area are incredibly dry.

    It's not really clear in my photo but the DPM is interesting. More like a very high density rubber honeycomb, around 10mm thick. Presumably give a bit more isolation from sever shaking.
    • CommentAuthorowlman
    • CommentTimeMay 28th 2025
     
    This certainly looks a high quality build, if different. Traditional Japanese joinery has always been very good, but like everywhere else I guess it's a diminishing skill.
    •  
      CommentAuthordjh
    • CommentTimeMay 28th 2025
     
    Posted By: Rext's not really clear in my photo but the DPM is interesting. More like a very high density rubber honeycomb, around 10mm thick. Presumably give a bit more isolation from sever shaking.
    It looked like an airtightness gasket to me, which is why I was curious.
    • CommentAuthorRex
    • CommentTimeMay 29th 2025
     
    Cannot comment on air tightness; have no idea about those regulations.

    I am just always gobsmacked that when I see this kind of construction, I never seen a nail anywhere.
    • CommentAuthorJonti
    • CommentTimeMay 29th 2025
     
    Having worked in the construction industry both abroad (Finland, Norway and Switzerland) and here in the UK I can say from personal experience the industry here in the UK is simply awful. Poor management, bad workmanship and absolutely no quality control by authorities. It certainly wasn't like this in the 80's before I left but by the time I came back in the 2010's it had totally changed.

    High quality, affordable construction is very possible if there are the tradesmen and desire to do so.
  11.  
    Looking at the pictures above it looks like the components are factory cut and assembled on site. (The accuracy of the cuts and the fact that timbers seem to have numbers stamped on the end) This would make sense if timber frame is the normal mode. Either choose your design from the list and assembled on site or pay for bespoke design for extra, also factory cut.
    • CommentAuthorMike1
    • CommentTimeMay 29th 2025 edited
     
    Thanks for posting the pictures; an interesting insight.

    I went looking online and found a paper that includes some typical construction details, traditional & modern. From that it seems that, since 2000, steel timber connectors are required in new buildings to reinforce the timber joints. I'm therefore not sure whether the frame in your photos has all the reinforcement necessary, or whether someone still needs to go around and fit them. But interesting :)

    Here it is: https://www.researchgate.net/figure/The-ultimate-failure-of-post-beam-brace-connections-in-the-P-and-N-technique_fig10_362075279 Hirakawa et al (2022), Seismic Retrofit Technique Using Plywood and Common Nails for Connections of Low-Rise Timber Frame Construction. Buildings. 12. 1029. 10.3390/buildings12071029
    • CommentAuthorRex
    • CommentTimeMay 30th 2025
     
    Mike1,

    Cannot answer your question but this was obviously in a construction state, so assume that there are bits and bobs stil to be fitted.

    And yes, it is all factory cut material. But from my limited experience, don't think there is a lot of 'factory' involved. I have seen back-street timber workshops where they are cutting and using 'clamp-on' mortise tools.

    However, some of the big companies do have standard housing styles, so assume that they also have factory produced parts.
    •  
      CommentAuthordjh
    • CommentTimeMay 30th 2025
     
    Somewhere I saw something that said in Japan the lifetime of [timber frame] houses is set by regulation at around twenty years. So they presumably need to make and install an awful lot more timber frames than we do.
    • CommentAuthorphiledge
    • CommentTimeMay 30th 2025
     
    The last photo shows bolted steel fixings but with those fixings in place it would be a bit cumbersome to add any further fixings/reinforcement?? I guess the steel fixings in the photo are the only ones??
    •  
      CommentAuthordjh
    • CommentTimeMay 30th 2025
     
    I don't think those fixings would get in the way of the nail plates shown in the article? Or the suggested plywood nail plate?
    • CommentAuthorJonti
    • CommentTimeMay 30th 2025
     
    <blockquote><cite>Posted By: djh</cite>Somewhere I saw something that said in Japan the lifetime of [timber frame] houses is set by regulation at around twenty years. So they presumably need to make and install an awful lot more timber frames than we do.</blockquote>

    its 30 years for concrete. However, I believe this is expected lifespan and it is not the case that buildings must be replaced after this time. In reality, with the correct maintenance a timber frame structure can be good for centuries as many examples around the world show.
    •  
      CommentAuthordjh
    • CommentTimeMay 31st 2025
     
    Ah, it was wikipedia - "An unusual feature of Japanese housing is that houses are presumed to have a limited lifespan, and are often torn down and rebuilt after a few decades, generally twenty years for wooden buildings and thirty years for concrete buildings"

    Yes agreed that timber frames can last for many many years. But if the norm is to replace after twenty years then there must be an awful lot more timber frames made there than here.
  19.  
    Most volume housebuilding near me now seems to use factory made timber frame wall panels, that are assembled on site onto the foundation slab. The roof is assembled on the ground nearby using factory made trusses, and then craned on top.

    But yesterday I passed a site where the roofs are being assembled on their actual foundation slabs, without the walls being in place yet. I am curious how they are going to get the wall kit in place underneath the roof.
    •  
      CommentAuthordjh
    • CommentTimeJun 1st 2025 edited
     
    Posted By: WillInAberdeenMost volume housebuilding near me now seems to use factory made timber frame wall panels, that are assembled on site onto the foundation slab. The roof is assembled on the ground nearby using factory made trusses, and then craned on top.
    The same techniques is sometimes used when building straw bale houses, to protect the straw quickly. It's also safer for the tilers!

    But yesterday I passed a site where the roofs are being assembled on their actual foundation slabs, without the walls being in place yet. I am curious how they are going to get the wall kit in place underneath the roof.
    Interesting! Is the site restricted so they had to reuse the same space? Can they move a roof to a spare space, crane in the walls, and then put the roof back in place? Photos would be interesting, as would a follow-up once you know what they do :)
    • CommentAuthorowlman
    • CommentTimeJun 1st 2025 edited
     
    For single storey, raise with a crane, or maybe jacks?, a few strategically placed props or SIPS and infill the rest. I guess it would save space having to have separate assembly areas. On a volume build it could speed things up no end.

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