Low Cost Fill Materials

One key to affordable natural building is to use low cost, locally available materials. Look especially for what others don’t want – things like ‘problem soils’, dredgings, ‘wastes’. This brick making video was the inspiration for this blog post. It explains how a company in the Philippines uses abundant, locally available materials to make brick. They use silt and clay that accumulates in rivers and reservoirs. Removing the silt and clay helps reduce flooding as well as provide low cost building materials for their bricks. The same material would work for earthbags, earthen plaster and tamped earth floors.

Other examples of low cost fill material for earthbags include: subsoil (also called fill dirt by excavators), clay, caliche, road base, crusher fines, crushed limestone, sand, scoria, pumice, gravel, dredgings (this includes silt and clay as explained above as well as crushed coral and sand from marinas).

9 thoughts on “Low Cost Fill Materials”

  1. I am in the process of planning an earthbag build in a jungle region in Ecuador. Heavy clay soils are abundant where we live, as are large rivers full of rock and river sand/fine gravel.

    I am hearing from some sources that gravel can be used as a fill material for earthbag building. I am apprehensive, as there is nothing in gravel to bind it together, but I wanted to ask an experienced source if it were possible? Even if it is, I am not sure I’d want to use gravel in an earthbag build, especially a larger one like we have planned.

    I am curious about the possibility of using river sand mixed with a bit of lime to make a sort of light, natural cement. Clay would be hard to mix with the sand, but lime is fairly cheap where we live and it would be easy to mix sand and lime to get a good mix. I’d have to play with ratios to see just how much lime would be needed. If it could work though, they would be easy materials to work with.

    Other option is just to go with the heavy clay soil. Temps fluctuate between 70 at night, and 85 to 90 during the day. Humidity bounces back and forth daily as well, from 70% up to 80% on average (with 100% humidity when rain is around a long while, which is fairly often in the rain forest). The only concern there would be how much heavy clay soil expands/contracts in such small temperature swings. Humidity changes so often I feel the walls would reach some sort of balance, though when we have weeks of rain at a time, the humidity would stay high for prolonged periods of time. No winter here, as we are on the equator, so those really are the only concerns climate-wise with a heavy clay bag-fill.

    Trying to use the materials we have on-site, and those are my two options.

    Any advice/guidance would be most appreciated!

    Is river sand and lime for bag-fill viable? I intend to sandwich the bags between wire mesh inside and out, and do a ferrocement outer shell and a natural plaster finish inside.

    • Gravel is recommended for fill only on the first few courses of bags to assure that moisture is not wicked up into the rest of the wall. Sand could also be used for this. If you do this, I suggest double bagging those courses to help assure that the fill will be confined over time.

      Clay alone is not a good idea because of the potential for expansion and contraction, but clay mixed with sand in a ratio of no more than 1:2 can work fine. Sand mixed with lime as a stabilizer can also work well. Most earthen fill materials can tolerate a good deal of humidity without deforming or supporting mold.

      You plan for plastering the inside and out sounds good, although I would prefer a synthetic mesh rather than wire because I think it will last longer and be more benign energetically.

  2. Thank you, gentlemen.

    Yesterday, while researching this, I came across a very old newspaper article on something called caliche block & tile by Howard Scoggins.

    I guess there’s many hours of research that can go into it. I don’t recall anything about it on your blog but the earthbag method is likely a much simpler approach. BTW, I apologize if I am posting these comments in the wrong area… its just an article I came across when querying caliche.

    The above mentioned article can be found here…


    Finally, Owen, I loaned the DVD I purchased a year or two ago out & never got it back so I need to buy another one. Before I do, though, are there any new ones about to be released? My plan is for using the Rachel tubes from Canada, last I looked into it.

    Thank you.

    • The definitive caliche expert and report is from the Center for Maximum Potential Building Systems:

      This info could be applied to earthbag building. But most any subsoil will work fine in earthbags. That’s a key advantage of building with bags — a wide range of materials will work.

      No other DVDs are planned. I may do one on our sustainable homestead eventually after I get lots of content and everything is built.

  3. Dozer work pushed up huge piles of caliche from right where house is to be built… good or bad… we’ve a natural caliche pad to build on.

    Any advice on getting started?

    There is no topsoil anywhere around the building area… its like a quarry… my concern is lack of flow.


  4. Hi again.

    Do we have any good/crazy/far fetched ideas what to use as insulation except (scoria, pumice). Sweden dont have that much vulcanos.

    Well I have one locally produced “rock”. Its glass that is heated and poped like popcorn I guess.
    http://www.hasopor.se/ (Swedish)

    Not that cheap.


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