What is the lifespan of poly bags, and will they make durable foundations? From our experience and from what we can gather from other sources, poly bags can last almost indefinitely if kept out of sunlight, and therefore double-bagged foundations appear to be extremely durable. This is important because earthbag foundations are much lower cost than concrete foundations.

One report said 30-year-old polypropylene bags were recovered from a landfill and they were still in good condition. This is approximately how long poly bags have been in existence. We also know from anecdotal evidence that moisture does not seem to adversely affect the poly material even after years of contact with wet soil and natural swings in temperatures, including harsh freeze/thaw cycles.

A Federal Highway Administration (FHWA) study concluded that the half life of polypropylene fabrics in benign environments could be 500 years or more.

[Note: this information is from a GeoMonolith report at GCSwall.com. We would like to find the original FHWA report in order to check the facts. If anyone has time to locate this report, please let us know. You could easily talk me into a free book for your trouble.]

Update: One of our readers who goes by the name Thomas has just won a free earthbag building book. Thomas located the original report we were looking for. Actually, there are four reports that analyze 24 exhumed samples from 12 sites. This government study should provide very compelling evidence about the durability of geosynthetics (poly bags). Thank you Thomas. We’ll get the article and summarize the report here at a later date.


Comments

Durability of Polypropylene Bags — 21 Comments

  1. Thank you for sharing the information!
    I have been arguing with someone recently, and I just want to prove that earthbag construction can last a lifetime.
    Unfortunately, I wasn’t able to locate your quote, “A Federal Highway Administration (FHWA) study concluded that the half life of polypropylene fabrics in benign environments could be 500 years or more.” anywhere, except here.
    However,as earthbag construction involves using PP bags, there is a study that suggests that geosynthetics can last between 25 and more than 100 years. Here is the source: https://ntl.bts.gov/lib/17000/17900/17975/PB2001105580.pdf (page 49).
    On the downside, this can’t help me prove my viewpoint, which is that earthbag homes should last a lifetime (as in “as long as the person who constructs such a home lives”)…Do you have any other sources I could use in this debate?
    Thank you!
    Maria

  2. Thank you for this absolutely useful information. Thank, you, thank you.

    Oscar Guillermo. Caracas, Venezuela

  3. how about those second hand poly bag used for flour, fish food etc?
    should we use that or buy new? very hard to get poly/raschel mesh roll here in south east asia

    • They all probably come from China now. Check the biggest cities near you. They’re used for dozens of things so they are available.

    • Do not buy laminated bags. That means they have a plastic liner that will prevent them from them drying out and getting hard.

      New bags will likely be stronger than used bags, but sometimes I used recycled bags if I know they are in good condition (stored out of the sun).

      • thanks Dr .. if i can customized the bag width ..whats the best width for tropics if i want to add rice hull & perlite to the dirt mixture?

        • 18″ width is standard. After the bags are filled and tamped the walls will be about 15″ wide. This creates a stable wall.

          No need to mix these other ingredients in with the soil. That’s just extra time and effort. Instead, shade the walls with wide roof overhangs and use the thick earthbag walls as thermal mass. Our earthbag roundhouse stays the same temperature night and day yearlong in the tropics because of this. Be sure to read previous blog stories about Passive Cooling Strategies that list dozens of related techniques to keep houses cool in hot climates.

          • meaning that extra insulation (for wall) is just a waste of time & effort?

            17″x 50″ should be better right Dr? more overlap
            i know from your e-book standard size 18″x30″

            cant get tube roll (at least for now)

          • No reason for insulation in the tropics if you keep the sun off the walls as I said.

            That size is fine. The extra length is an advantage due to the larger overlap.

  4. “therefore double-bagged foundations appear to be extremely durable” Do you mean putting one bag inside another and then filling them or do you mean having one layer of filled bags and then tamping another layer of bags on top of the first layer in a perpendicular direction?

  5. My best research has lead me to FHWA-RD-00-157
    Long-Term durability of Geosynthetics based on exhumed samples from construction projects.
    NTIS No. PB2001-105580

    For a description of the contents:
    http://www.thefreelibrary.com/Long-Term+durability+of+Geosynthetics+based+on+exhumed+samples+from…-a082784275

    Unfortunately the publication is $15 for a digital copy as its least expensive option. http://www.ntis.gov/search/product.aspx?ABBR=PB2001105580

    • Wow, I’m impressed. We’ll have to get this document and recap the main points on our blog.

      What can I do for you to show my appreciation?

      Update: I just made this announcement on the blog post: you’ve won a free copy of my upcoming earthbag book. I’ll send it when it’s finished in about one month.

  6. They may last that long, but would you endorse using earthbags for a foundation instead of the typical gravel-filled trench? Just curious, really.

Leave a Reply

Your email address will not be published. Required fields are marked *