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  • 1.  Building a Real House Out of LEGOs (sort of)

    Posted 02-08-2021 07:57 PM
    Edited by Ari Daniels 02-10-2021 11:56 AM

    TLDR: Anyone have any experience with, or strong interest in, aircrete/cellular lightweight concrete and its application in a residential construction project? We're forming cinderblock-sized LEGO-style blocks out of aircrete and constructing a single-family house out of them. Reply to or follow this thread and once I start adding updates/videos/materials on the project, you'll be able to keep updated. Also, I'll happily take criticism, as long as it's constructive.

    Background: My partner and I are going to build a house. During a thorough and circuitous "how are we going to do this?" discussion stretching over months, I just conversationally mentioned a building system developed somewhere in northern Europe I had come across browsing the Internet that was basically lightweight cementitious blocks, allowing a sort of modular build like stacking LEGO bricks. Her eyes lit up, probably for the first time during a many-months-long preliminary planning process. My partner loved Legos as a kid and still has her set from 3+ decades ago. We had, to that point, been talking about mostly conventional stick-built options.

    Material: This material goes by many names – cellular lightweight concrete (CLC), low-density cellular concrete (LDCC), foam concrete (or "foamcrete"), aircrete, sometimes autoclaved aerated concrete (AAC) if produced by a specific process, etc. I'll call it aircrete since it rolls off the tongue, and since I'm mostly playing off the Domegaia processes, and likely a few of their tools. I like what they're about, attempting to address the fundamental housing needs of the world, and making the process accessible to nearly everyone. (I won't be building a dome home, though.) We are doing this in a very "anyone can do it" fashion. As far as material properties, aircrete has much better insulation qualities than concrete, lower-but-still-plenty-strong compression strength, and what it lacks in bending/shear relative to concrete is balanced by its workability, being more similar to wood than concrete in terms of cutting/drilling/routing.

    Basics of the build: So I started looking into ways to transfer the technology to residential home-building in a practical way, and a way that's at least somewhat likely to pass through local building and zoning/code constraints. What I landed on was blocks basically the same size as a standard concrete block ("cinder block"), about 8"x8"x16". This way things like crawlspace/basement vents and other existing, off-the-shelf building products are applicable for our project, and each block is very manageable for almost anyone at roughly 15-20 pounds. There will be other sizes as well, roughly mimicking Lego's general brick varieties (2x4, 2x3, 2x2, 1x4, etc.), and these will have nubs and recesses very similar to Legos so they interlock. The house, 32'x40', one story, will take somewhere on the order of 3,000 blocks.

    More specifics on the build: This will be dry-stack block work (no mortar between blocks except as necessary to correct level and plumb) with a surface bond inside and out using a poly fabric and denser plastic mortar for the bond and sealant. I figured on having chamfered corners on some or all of the blocks so we could route cable or pipe inside the walls without having to rout channels for every pipe or wire. [EDIT: clarification - when I say "inside the walls," I mean on the inside surface of the walls. There are only a few places where this will occur on an exterior wall, but the walls themselves are solid insulation.] There will be a number of energy-efficient systems incorporated, designed largely to minimize energy use by preventing heat loss. The floor system will be pretty conventional but will include hydronic radiant heating including a heat exchanger in the wood-fueled masonry heater in the center of the house. The roof will be fairly standard, with I-joint framing, and a clear story for light and a little visual appeal. We're deciding between a tried and true ribbed metal roofing and an experimental aircrete with sealer/hardener/densifier for a little sound insulation relative to the metal.

    The fun: While I basically modeled the house in AutoCAD Architecture, we also found a Lego reseller on Etsy and ordered a very large custom set of Legos, and we're building a scale model of the house in 3D. (Really, it's to scale in 2D/layout, but not 3D/elevation, because Legos bricks are not as tall as they are wide.)

    If you have any thoughts on this, drop them here. If you're interested in being a part of the experiment in some way, send me a direct message. If you want to stay informed on the development of the experiment and process, and the results as we get moving this Spring, follow this post/thread.


    LEGO model, in 2D scale, of the house we are going to build.

    Layout of the bathrooms
    Layout of the laundry room

    Ari Daniels, P.E., M.ASCE
    Outland, LLC - Owner/Principal
    Center for Watershed Protection, Inc. - Water Resources Engineer
    Monterey, Virginia, USA

  • 2.  RE: Building a Real House Out of LEGOs (sort of)

    Posted 02-18-2021 09:05 AM
    I wish I had something constructive to add here, but mostly I am commenting so that I can follow your project as it progresses!

    Christopher Seigel P.E., M.ASCE
    Civil Engineer