The PlyPad: CNC Machine Yourself A Tiny House

The Maslow CNC project is a CNC mill for sheet woodwork that is designed to be as inexpensive as possible and to be assembled by the end user. They’ve dropped us a line to tell us about a recent project they’ve undertaken as part of a collaboration to produce the PlyPad, a tiny house for Kenton Women’s Village, a project to tackle homelessness among women in part of the City of Portland.

Their write-up is a fascinating look at the issues surrounding the design and construction of a small dwelling using CNC rather than traditional methods. As an example their original design featured an attractive sawtooth roofline with multiple clerestory windows, but sadly a satisfactory solution could not be found to the problem of keeping it waterproof and they were forced to adopt a more conventional look.

The walls of the building are a ply-foam bonded sandwich, and the house is constructed in 4 foot sections to match the width of a sheet of ply. There are several section designs with built-in furniture, for example containing a bed, or storage space.

This house was designed to be part of a community with central washing and sanitary facilities, so it does not incorporate the bathroom you might expect. However it is not impossible to imagine how sections could be designed containing these, and could be added to a full suite of construction choices. We are reminded of its similarity to the WikiHouse project.

We covered the Maslow project back in 2016, it is especially pleasing to see that it has been something of a success.

58 thoughts on “The PlyPad: CNC Machine Yourself A Tiny House

  1. Hmm, this approach might well be applicable to accelerate the conversion of my 40ft Mercedes
    bus of late 1980’s to a fully massaged motor home, does seem to offer many potential congruent
    paths – well if I can fit living space into all the tech stuff I want to make it run on the smell
    of an oily rag with Fronius inverter, 10Kw solar array and chem lab to collect syngas & turn it
    into high density butanol/diesel like mix – great fun aye – thinking about local wifi for all controls ;-)

    Seriiously this has merit in all sorts of areas, which should have some utility in not just my motorhome
    projects but light transport type living as well as transportable and cost effective assembly beyond
    the first world, interesting, thanks :-)

      1. Tesla says their truck will run at just under 2 Kwh per mile, so a 10Kw solar array in full sun should be able to manage to drive a tesla truck drive train at 5 mph for as long as there is sunlight.

        Never mind a 40ft bus that is 10 ft wide would only have ~37m^2 of roof, and at 200w per square meter you aren’t going to break 8Kw on the roof so not sure where the other 2Kw’s are going to go on his bus.

    1. Hmm yeah well BrendaEM,
      F..k em frankly, they won’t be following me around on the roads across
      localities though you have a point that I can thumb in their noses so well :-)

      Actually whats interesting re your comment is it provokes me to consider the
      various regulatory groups are so easily being sidestepped more these
      days as if like banal religions – they are becoming irrelevant/facile in so many ways
      & beyond the obvious as if its some anarchic start of a wider casual freedom when
      tech/trick can be applied easily & creatively but, carefully too so as not to set the ire of
      the robotic functionaries (confused as conscientious humans) we may encounter
      sporadically in bureaucratic systems which started as a facile trend as far back as
      60 years ago – diversity rules, perchance the means to dream of change beyond
      most people’s contraction zones, Shakespeare anyone :P

      The benefit of red whine, jarlsberg cheese & glazed ginger/aniseed – apologies ;-)
      Back to real stuff after a good nights lucid dream sleep & meditation cycle :shrug:

      Happy New year, though if religion/politics feels threatened – then Happy New Fears :D

    2. More specifically it’s not what Building Inspectors want you to do.

      These things are like gathering wood for a fire (with a little styrofoam thrown in for good measure) and then living in it.

      1. Yeah, that was what got me depressed about this project. I would love to see something like this used by a group of tech-savvy poor millenial-types as housing pods in a larger building like a warehouse, but they are just box-shaped pieces of kindling.

          1. All those neat skyscraper fires in the news last year with the flammable cladding were covered in polyisocyanurate. It might have a higher heat tolerance, good for a water heater or the like, but it’s not going to provide any benefit in a fire.

    3. The FHA has been around for decades, requiring any single family structure being built with gov’t lending to meet their minimum requirements.
      But those requirements add quite a bit to the cost of a minimal dwelling.

      1. I mean you could build a mud and straw shack for a lot less than a properly engineered structure.

        But every time there is anything like winds over 10 miles per hour, rain, snow, cold, heat, anything requiring occupants to be able to leave quickly, disability considerations, sunlight or basically any other natural condition, those “structures” tend to either not protect anybody, are constantly falling apart or can even cause major issues. Having a structure that is also literally made from materials that are a growth medium for mold and mildew that you live inside for most of your day or night or both is not healthy for the occupants.

        We are not even talking about somewhat uncommon but otherwise adverse conditions here. Fires, floods, hurricanes, etc. There is a reason why some countries recover from natural disasters much better and more quickly than others and building codes at least make sure that generally agreed upon minimal requirements are being met. Travel to some third world countries and take a look at the infrastructure. Some of it is…. quite, well, interesting. It’s basically hacked together and sometimes that is generous.

        That all said, minimal requirements are often times still not very good either. In the USA, wood frame walls with R-Values of only 13? I guess it’s better than zero and R-values do not tell the whole story regarding insulation but different countries do things differently and on the whole, having some generally agreed upon minimum standards do add cost but they do so with generally good intentions for the community as a whole and it (to a degree) levels the playing field such that you don’t wind up with every home being the equivalent of a cheap Chinese made car that does this when it impacts at under 40 miles per hour.

        1. you rail against R-13, but I’ll point out that the amount of insulation that makes sense can vary drastically depending on where you live.

          Passive home builders are starting to realize that it’s more cost effective to have a heater/AC with solar panels than to keep adding more insulation.

          R-26 vs R-13 means that 1/2 as much energy leaks through the walls
          R-52 vs R-13 means that 1/4 as much energy leaks through the walls

          But a R-52 wall is far more than 4x the cost of a R-13 wall.

          And if the temperature outside is comfortable, a R-0 wall is sufficient.

          There are parts of the building codes that make sense in terms of safety. But there are a lot of other parts of building codes that have nothing to do with safety, and are much harder to justify.

          Making houses more air-tight has advantages for energy efficiency, but serious disadvantages for air quality. The last decade or so the building codes have been emphasizing energy efficiency over most other things (including cost effectiveness and air quality)

        2. Mud and straw are not amenable to engineering. Well, they are not really suitable building materials. You can engineer them but they are still not great building materials to start with or work with. I guess you could make blocks out of them?

          The amount of insulation that makes sense can absolutely vary drastically depending on where you live. No question there.

          A R-0 wall is “sufficient” when the temperature outside is comfortable or you possibly have other means of generating warmth or cooling. The issue is that it rarely stays that way for long periods of time. It’s similar to why some municipalities have more stringent building codes to deal with uncommon things like hurricanes.

          You are correct that there is a rate limiting point at which simply adding more R-value starts to become less and less reward for effort made. But my argument is that most all homes should have more than R-13 insulation as a minimum requirement is all. Depending on where the structure is located of course. Also, R-values are only part of the energy transfer equation anyway. You could have R-70 and have a very drafty structure and it would sharply negate the insulation’s ability to prevent energy transfer.

        3. BTW that’s a Korean car from the late 90s, not to shut down your thing with china regulations but they’re rife with corruption in many sectors certain permits can be bought or given depends who the owner of the company bows down to.

  2. One has to wonder why they use plywood on the interior walls. If they sandwiched T111 plywood outside, and 1/4 inch drywall inside that they would save a lot of money and weight.

    That way, the outside is already sided, and thou just need to spackle the interior seams.

    1. Structural integrity? They are using t-slots to couple everything together and drywall would not support that. Also not sure how to CNC process drywall off hand though it presumably can be done.

      1. 1/8″ spiral saw bits for drywall cutting should work for CNC, the bit has to go through the work piece so you have to figure out how to have 1/4″ of clearance on the side opposite the spindle. My guess is you’d want to be vacuuming up the dust as it cuts.

        1. Yeah I own a CNC router that can cut 4’x8′ sheets of plywood and I have to say that it would be good for making a jig fixture but there’s no advantage to using CNC unless your heart is set on curvy lines. The most cost effective and expedient way is still straight cuts using a circular saw hands down.

          1. davidelang – this is a common misconception about CNC machines. why do you think circuit boards are mostly made in china, even though every step is automated? you don’t wait around for the CNC to finish, you wait around for your cue to load the next sheet in. if you don’t actually need the intricacy of a CNC shape, it’s typically a lot slower and a lot more labor intense than simply using a carpenter. your real choice is a three way:

            * cut the wood yourself
            * pay a carpenter to cut the wood while you wait
            * put in a ton of extra work feeding and maintaining a CNC machine that isn’t improving your finished product and in fact is forcing you to use sub-standard components

            though fwiw the idea that plywood is kindling is nuts, even though it’s not the best interior surfacing. plywood can be lit but not as easily as kindling can. you can blowtorch the face of a sheet of plywood for a while without catching a self-sustaining a fire – kindling catches and sustains almost immediately.

          2. @GregA

            As a commercial endeavor, you are absolutely correct. But as a hobbyist, you are absolutely wrong.

            If you are trying to make a living building structures, then a slow, hobby CNC like the maslow is not a tool for you to use. There is a good reason that ShopBot sells a 4×8 CNC router for $20K and sells a lot of them (and why some shops will spend well into the 6 figures for a 4×8 woodworking CNC.

            But when you are volunteering or doing hobby work, your time is MUCH cheaper, and projects like this one make far more sense.

          3. @davidelang It looks like a complete maslow machine might run around $500. So You could be running around 40 of them for that $20k. You could have a machine at each build site instead of moving the machine or materials around.It would be interesting to see a more complete comparison of the serial vs parallel build methods in action.

          4. @Delgir
            the maslow is limited to cutting at 30-40 ipm, the big machines can finish cutting as fast as you can unload the cut parts (in fact, some of them have two beds so you can be unloading on one side while it’s cutting on the other)

            Also, the maslow is a hobby machine, it needs more care and feeding and will have more things go wrong with it than the big machine.

            I’m a huge supporter of the maslow, but I don’t try to pretend that it’s a replacement for the big machines

            (also, running a bunch of maslows will take a LOT more space and power than one big machine)

            We are working on variations of the maslow that are easier to transport.

            And remember that the plypad design specified that each module needed to be able to be transported via forklift, so gain the efficiency of centralized production in a nice environment, and transport the results as needed.

    2. I think its cause these units are modular and are being moved around, any twisting of the frame and the drywall is going to crack where plywood would flex, also since these units are basically a shed they would be more prone to moisture not something you want around drywall.

    3. If you have ever built a structure that is exposed to rain or snow or both, you would run away from T111 and never ever look back. IMHO it is a truly awful material. I built a tiny house and used marine plywood to skin the outside of it, with recycled vinyl siding over that. The inside is all rough cut from my mill. The floors are recycled hardwood. The framing is a mix of old and new material. Doors and windows are recycled. If you look around there are a lot of good materials you can scarf up for the cost to tearing things down, and having even a very modest sawmill lets you turn logs into nice lumber.

      I do really like the Maslow router though. I may get one come spring.

  3. There are a bunch of projects that are doing CNC housing wikihouse.cc being one that I followed for a bit so it is feasible but Im not sure that a hanging plotter design is right for this type of project, If the main reason is space saving then wouldn’t a CNC designed more like a vertical panel saw be better? Cost would be a bit higher but speed and a Z would make it worth it IMO.

    1. The maslow has a Z axis.

      As for other designs, the question is a matter of cost vs performance.

      The Maslow is designed to try and be as cheap as possible to make it affordable for people to build. If you are doing this as a hobby, “faster but more expensive” frequently translates into “too expensive”

      look at 3D printers, cheap ones are now below $200, and you can easily spend 10x that much on one. But the fact that the more expensive ones are faster, more accurate, and more reliable doesn’t eliminate the market for the cheap ones.

      And if it hadn’t been for the cheap, unreliable 3D printers that were produced, there wouldn’t be the market for the expensive, high-end ones that are currently available.

  4. I’m all for CNC. I bought myself a big Shopsabre router with money that I could have spent on on a matching-numbers Chevy SS Camaro. Or hookers. But this project is just playtime for maker-hipsters. People who need Tiny Houses, (or huts, as we used to call them,) are building ingenious, functional dwellings all round the world in favellas and refugee camps and communes from whatever is available. And that is the whole point. Availability. What are housing-deprived expected to do? Pop along to their local makerspace pay the $50 monthly subscription plus laser-cutter time? Or just use whatever plywood, tarps and brad nails they can get hold of? Let’s have a bit of old-school reality, here.

    1. Remember, this was an official project by the city of Portland to have designers create designs for getting the homeless protected (and in a way that looks halfway decent and can be moved)

      Huts, tents, etc are what they were trying to get away from.

      Was this a practical design? not really, and the actual writeup says so. There were things that worked and things that didn’t work. They made everything public so that other people could learn and/or improve the designs.

      1. How does one improve things though exactly? It depends on what your final criteria are but even beyond that, one has certain limitations to work within. Are you trying to minimize cost? Make it easy to produce? Modular? What is the expected use market and what codes does it need to meet? Are there major trade offs that must be made? Does it have to be CNC fabricated? Are there ways to improve that?

        Is it possible to rethink this entire model? Are there better materials or construction techniques that could be used instead? Or materials or methods that could work well at scale? In the US at least, the bulk of the residential building code seems directed at wooden and plywood homes that are one to three story in size. Is that the best approach or are there ways to improve things?

        Has anybody come up with a LEGO block style of building that meets relevant codes? I have seen factory made homes that are assembled on site being very viable and are hardly modular homes.

        1. It gets them away from sleeping on the ground as that’s how most homeless get sick.
          Though I think making something like a lite version of the Dymaxion home out of metal and plastic would be better than wood for low cost housing.
          Have it where it goes together using common hand tools.

          1. Conceptually similar to bricks but easier to install without skilled labor and capable of sustaining in-plane shear forces. Also, something largely structural and not just used for exterior cladding.

            More like this as one example.

          2. bricks have been historically used for structural use, not for cladding. And there are robots that lay bricks.

            using bricks as cladding is a pretty recent ‘innovation’

  5. What I find slightly puzzling is that something as complex as that sawtooth roof with clerestory was their go-to design, rather than simply cutting widows into the walls. It would be easier for the occupant to add curtains, and the top of the dwelling could be made from flat sheets of Colorbond or some other corrosion-resistant sheet-metal roofing.

    1. The maslow folks didn’t create the initial design, that was done by “and award winning design firm” trying to show off to the city.

      design firms focus on things that look pretty, not on making them practical to build :-)

  6. What could be looked at is modifying the methods used for modular prison cells. Each cell is built of cast concrete with wiring for a light, water supply and drains for a sink and toilet.

    For housing units the construction could be lighter. They’d need more wiring for outlets and lights. More windows too. The, sink, toilet and other fixtures would be lower cost home grade instead of the indestructible stainless steel prison type.

    Yet another option would be to have a company that builds freight containers make some that are 8×12 and the “High Cube” 9.5 foot height instead of the regular 8 foot. Lighter gauge steel could be used, even when stacking, because they would never be stuffed with several thousand pounds of cargo, nor would they need to be strong enough to withstand being on the bottom of a stack of other heavily loaded containers.

    1. Prisons are anything but cheap to build and not very homey feeling.
      I think Buckminster Fuller hit on the solution back in the 1940s.
      https://en.wikipedia.org/wiki/Dymaxion_house
      The full size Dymaxion house was only 3,000lbs a 1/4 size one of only 250 sq ft could be gotten to under 1500lbs even if lower cost steel was used.
      I’d set a design goal to have it be transportable by a standard pickup truck or full sized cargo van.

  7. Possibility of revising the clerestory design and sticking holes into the roof with a PTFE bottle filled with water and some bleach to let in light frome there. Additional modification would be to add a solar powered LED in those lights.

      1. Yeah, but caulking js getting better. He no doubt saw this technique used in areas without ekec fir lights. Some have a biz installing these water bittle-“lights,” paid for by the gov’t.

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