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BS* + Beer

Concrete-Free Slabs

The benefits and detailing of slab assemblies that eliminate concrete

There are lots of reasons for builders to love concrete. It is a strong, durable, and affordable building material with uses everywhere from the foundation to the finished surfaces. There’s also one big reason for green builders not to like it very much at all: concrete comes with a big carbon footprint.

It’s easy to choose not to use concrete for a patio or countertop—for these details there are plenty of good alternatives—but more difficult to figure out how to get it out of the foundation of a home. One step some builders have taken is to eliminate it from the slab—including both slab-on-grade homes and basement slabs.

In recent months we’ve shown examples of this in homes designed by Michael Maines and Randy Williams, who were both part of the this week’s discussion on the same topic on The BS* + Beer Show. Other panelists included Steven Baczek, Architect; Steve Demetrick, Demetrick Housewrights; Elizabeth DiSalvo, Trillium Architects; Andy Engel, Roxbury Cabinet Company; Josh Salinger, Birdsmouth Design/Build; and Randy Williams, Northern Built Pro. We hope you enjoy the show.

Many articles were mentioned in the episode. If you are interested in reading more, here are the links:
Steve DeMetrick was kind enough to provide us with his notes on concrete-free slabs, from his experience building them in Rhode Island. You can view the document here.
Next show April 23, 6 to 7:30 pm: Is It Time To Consider Panelized Walls? with Tedd Benson, founder of Bensonwood, Unity Homes, and Tektoniks; and David Schleicher president of Prairie Design Build. Watch GBA and FHB newsletters and social media or check back here next week for more information on how to tune in live.

Brian Pontolilo is a former editor at Fine Homebuilding magazine and Green Building Advisor.


  1. jackofalltrades777 | | #1

    China produces more than 1/2 of the worlds concrete production and that is expected to rise with more highway and buildings going up in China.

    China is killing us off with its viruses like COVID and they could care less. They are killing us off with their pollution discharge and they could care less.

    The problem is not our use of concrete in the USA. It's China.

    1. Expert Member
      MALCOLM TAYLOR | | #2

      Rank Country CO2 emissions (per capita)
      1 Saudi Arabia 16.3T
      2 Australia 16.2T
      3 United States 15.0T
      4 Canada 14.9T
      5 South Korea 11.6T
      6 Russian Federation 9.9T
      7 Japan 9.0T
      8 Germany 8.9T
      9 Poland 7.7T
      10 South Africa 7.4T
      11 Islamic Republic of Iran 7.1T
      12 China 6.4T

      1. jackofalltrades777 | | #4


        China used more cement between 2011 and 2013 than the US did in the entire 20th Century.

        Nobody says anything about aviation fuel which was around 3% of CO2 in 2019. Instead of banning concrete, ban or limit air travel. If we did that we wouldn't be seeing COVID19 on our continent. A virus cannot travel across an ocean without modern air travel (ships are a concern but not like planes).

        1. Expert Member
          RICHARD EVANS | | #5


          I follow a number of prominent environmentalists on Twitter. Reducing air travel is brought up constantly. The Tree Hugger website has an entire section devoted to aviation:

          I'm not sure I want GBA reporting on flying habits, etc. as I think it should be focused on green building. Concrete slabs may not save the world but it's a positive step in the right direction for the Green Building community- which of course is what this website is all about. :-)

    2. Expert Member
      Michael Maines | | #6

      China has twice our CO2 emissions but four times our population, and a significant portion of their emissions are for making stuff that westerners buy. On a per-capita basis, as Malcolm noted, Americans are by far heavier CO2 polluters than Chinese citizens.

      Reducing the amount of concrete we use on a single project is obviously not going to make a measurable difference regarding climate emissions. Likewise, whether or not you throw your fast-food trash on the ground, or drive a vehicle that gets 10 mpg, or if you fly to a vacation twice a year--none of that is going to move the needle one iota.

      BUT--if you are presented with two equal options, which should you choose: do I reduce my contribution to the climate crisis, and show others how to do the same, or do I go ahead with business as usual? Do I throw my trash on the ground because it's easier for me, modeling my behavior for my kids, or do I take bit of extra effort and dispose of it properly? Do I reduce my fossil fuel use or do I "roll coal" because I like to stick it to the man? Do I fly to an all-inclusive resort or support my local economy?

      I believe that every decision is important, even if not every decision makes an obvious difference. If you listen to our show, I think you'll see that we all have reasons besides carbon emissions for reducing our concrete use. (You'll also get to see Steve Baczek roast me for saying that when low cost to clients is the most important thing, I still do full concrete slabs!)

    3. jollygreenshortguy | | #14

      Let's keep in mind that much of the energy use and related emissions in China is in order to manufacture products used in western countries. When we buy products "made in China", though the emissions may be shown "on the books" as having come from China, they are a direct result of our decisions to purchase those products.
      Offshoring the emissions from our own consumption isn't a solution.
      In short, it's complicated.

  2. Deleted | | #3


  3. Jon_R | | #7

    Anyone working to reduce carbon should know the "$/ton" of a proposal and how it compares to alternatives. Yet I didn't hear that phrase once.

    1. Expert Member
      Michael Maines | | #8

      Jon, we talked about relative costs, but perhaps not your exact phrase. In fact I believe that several of us noted that eliminating the concrete from our slabs was less expensive than including concrete, when there is a finished floor other than concrete. We had a large guest panel and only an hour (which stretched an extra 1/2 hour) to cover a lot of ground, without a specific agenda of things to discuss. I would have appreciated someone bringing up your specific point; maybe you should consider joining future discussions!

  4. forgottenben | | #9

    With there being no concrete would you still recommend against polyiso insulation under the plywood. I know polyiso is not recommended for under a concrete slab.

    1. Expert Member
      Michael Maines | | #13

      Unless it was an extremely dry location I would not risk using polyiso in contact with earth of any type. EPS (of the appropriate density) is a safer choice.

  5. malady | | #10

    Assuming you complete the shell first to minimize water on the concrete free floor system, how do you frame walls with no deck to stage on?

    1. Expert Member
      MALCOLM TAYLOR | | #11


      When we frame in the rainy season here in the PNW, we often leave the slab until the roof is on, especially with garages. It is a pain, and one of the things that makes it easier is sheathing the walls once they are up. I'd assume a similar approach would work with a concrete-less floor

    2. Expert Member
      Michael Maines | | #12

      On some projects the walls are coming panelized off-site. Otherwise you just make a flat area and build the walls like you normally would, with minor adjustments.

      On most jobs I've been on we do minimal interior framing, focusing on getting the shell dried in first, with only the most critical interior members put in place.

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