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Airkrete and moisture

Chris Johnston | Posted in Green Building Techniques on

I recently had air-krete installed in my new home which is under construction. Construction on the outside included OSB sheathing, rigid foam insulation, and a housewrap. I am confident drying from the inside to the outside is minimal if non-existant.

On the inside wall airkrete was sprayed in. A housewrap was put over the drywall side of the studs to keep the air-krete from falling out during installation. In accordance with standard AIr-Krete installation, the inside house wrap was slit 4-inches horizontally approximately ever 12-inches vertically. This was to help the air-krete dry.

According to Air-Krete the drying time should be 2 days. A week went by before my drywall started installing sheetrock on the walls. He did not notice any moisture. However, and approximately two weeks after the Air-Krete was installed, we found a stud needed to be installed on a wall to support a shower door. The housewrap was slit at that location, and the Air-Krete removed.

The Air-Krete was moist, like moist sand. It did not “drip,” but stuck together due to the moisture content. My drywall contractor was very concerned the moisture will damage the drywall, especially future installation of mud and tape. I contacted AIr-Krete headquarters and they have suggested installing a dehumidifier and heaters and stopping the drywall installation for at least a few days to let the Air-Krete dry.

I guess my question is, does this seem normal? Could I purchase a moisture meter with a probe and stick it through the installed drywall into the Air-Krete to see if it is dry, so I can verify the mud and tape can be installed since the Air-Krete is dry? And where do I get such a probe? I have seen meters for checking the moisture content of wood and drywall online, but they have short prongs. I know this may sound silly, but would a soil probe which measures moisture work?

Any help or guidance on what I should do next will be appreciated?

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Replies

  1. Riversong | | #1

    Do you mean "housewrap" which is highly vapor-permeable, or vapor barrier which is not?

    There absolutely should not have been an interior vapor barrier since not only are you adding considerable moisture to the wall cavities but - as you point out - the wall assembly cannot dry to the exterior.

  2. Chris Johnston | | #2

    It is house wrap. You can see it on their website. http://www.airkrete.com/trailer/InsideApplications/index.html

  3. Riversong | | #3

    If it's a breatheable material, then there should be no need to slit it every 12" in order for the AirKrete to dry.

    Keep in mind that a new house, built of KD lumber, already has an excess of 300 gallons of water just in the framing that needs to dry out. Adding additional moisture to the house is often not a good idea.

  4. J Chesnut | | #4

    I don't have field experience with Air Krete but have read about it several times.
    I don't think the slits were to allow the AirKrete to dry, they were only for installation.
    AirKrete should dry to a fragile dry foam consistency. AirKrete when installed vertically needs netting to hold it in place.
    Potentially your contractor incorrectly used a housewrap product as the netting that didn't allow the AirKrete to 'cure' correctly. Just a guess I could be wrong.
    Where are you located and what were the weather conditions during install?

  5. Chris | | #5

    I am located in southern Illinois, about 2 hours southeast of St. Louis. I have spoken with R. Keene Christopher, owner of Airkrete, and he has been very helpful. He said it will dry slowly, especially through the house wrap, and that is why they slit the housewrap - to facilitiate drying. I appreciate everone's response. I just assumed it would all be dry in two days. That does not seem to be the case. I would recommend not having your drywall installed until you confirm it is completely dry. In the meanwhile, we did install a space heater in one room for a test and it seems to be working - some wet stains on the drywall are gone. I may rent a commercial dehumidifier and run it for a while. I still may try sticking a moisture meter through the drywall into the airkrete if I can find one that will work. Again, any advice appreciate, and thanks for what you all have provided.

  6. Chris | | #6

    Oh, one othe item, the weather was dry when it was installed, and we have been in a two month drought.

  7. Riversong | | #7

    Chris,

    You're getting some kind of misinformation from AirKrete. If that is really housewrap (like Tyvek or Typar), then it is highly permeable to water vapor and won't inhibit drying to the interior. In other words, it does not need to be slit unless it's vapor impermeable like polyethylene. Did the installer use the wrong membrane?

  8. Chris | | #8

    The writing on the membrane reads "Easy Gard House Wrap, ICC-ES ESR 2252"

  9. Chris | | #9

    I found two discussions on line about "Easy Gard House Wrap, ICC-ES ESR 2252." The links are included below. The good news is it seems to be permeable to moisture. Today I rented a commercial dehumidifier and put it in the house to see if will facilitate drying.

    http://wiki.answers.com/Q/Your_contractor_said_he_would_use_Tvek_house_wrap_under_the_vinyl_siding_and_the_house_has_something_called_Easy_Gard_is_this_the_same_thing

    http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2252.pdf

  10. Riversong | | #10

    Easy Gard is a polyethylene housewrap, apparently perforated, that is made in China and sold at Home Depot.

    I'm not surprised that it needs to be slit in order to allow drying. Their ICC-ES statement says nothing about permeability.

    I would put that in the same dumpster as the Chinese drywall.

  11. Anonymous | | #11

    The slits are for both aiding in drying and access for installation. I am concerned that the HDPE wrap w/ a polyethylene coating (according to the ICC paper) may not breathe adequately on it's own. Tyvek is specified, because of it's moisture vapor permeability and is used in some installations. It would likely be prudent to aggressively heat the living space to promote evaporation and use your HVAC system to ventilate and exchange in fresh air. The dehumidifier is a good idea also. Air Krete is a fine product if installed correctly and cured without issue. It does not support mold growth, but wood and drywall do and moisture should be evacuated from the wall cavities asap. An IR scan may be able to help detect moisture levels as well.

  12. Chris Johnston | | #12

    Thanks. I am hoping the installed housewrap is more porous than Tyvek. The website below implies it is. Can moisture travel through drywall without hurting the drywall?

    http://wiki.answers.com/Q/Your_contractor_said_he_would_use_Tvek_house_wrap_under_the_vinyl_siding_and_the_house_has_something_called_Easy_Gard_is_this_the_same_thing

  13. Riversong | | #13

    Chris,

    No housewrap is more vapor open than Tyvek (too much, in my opinion). Easy Gard is a cheap Chinese product that doesn't offer any permeance specifications. But, given its construction, it's not likely to be a very effective weather barrier, and I suspect it doesn't breathe well which is why it was slit.

    As I've said repeatedly, a vapor-permeable housewrap does not require any slits to let the material behind it dry.

    There are two kinds of moisture. Water vapor, which is what housewrap is supposed to let through, can pass through drywall without harm. But liquid water will saturate drywall, weaken it, allow it to flex and sag and remain in that deformed position when it dries, and can cause mold growth.

  14. Chris | | #14

    Thank you Robert. Do you think it would be possible to get a moisture meter - perhaps a hygrometer with a probe, drill a hole through the drywall at random locations, and stick in the probe to see the current moisture levels in the wall cavity with the air-krete at various locations? Of course I am not even sure what the baseline moisture levels should be. Zero? Same as ambient air?
    I'm just trying to come up with a "scientific" way of making sure the air-krete is dry before my drywall installer tapes and muds.

    I realize the drywall should not have gone up before the Airkrete was dry, but I did not know that at the time. Installer told me to wait two days. Airkrete website says "several days." Airkrete Canada website says "24 hours." Bulletin to future Air-krete customers: verify with installer and "main website" installation will dry. Make sure barrier used to hold Air-krete in on drywall side is water vapor permeable - not just slit permeable. Make sure Air-Krete is completely dry before drywall goes up. Make sure contractor and main website give you scientific means of verifying Air-Krete is dry. I think it is a good product, and would install again, but just use advice I just gave. Don't want to end up like this link:
    http://listserv.repp.org/pipermail/greenbuilding_listserv.repp.org/2007-March/002621.html

  15. Chris | | #15

    Anonymous - thank you for the advice. I have one problem HVAC system is not online. The reason? HVAC contractor refuses to warantee system if turned on before drywall is completely done. Reason? HVAC contractor is very concerned drywall dust will damage HVAC system.

  16. Robert Hronek | | #16

    The house wrap is used to contain the Airkrete during installion. They have a video on thier site that shows it being shot through netting. According to Keene that was done at the request of the TV program so that the Airkrete could be seen during filming. The excess that was forced through the netting was scrapped even with the studs. A house wrap prevents any excess from coming through, thus no waste and no clean up. Nothing else ozzed out so it needed very little support on through the netting. I would say that if the Arkrete has set up, your house wrap can be removed. In the wall assembly it serves no real purpose, the painted drywall will serve as your vapor barrier.

    In fact I would say it is in your best interest to remove the house wrap. If the house wrap is impeding vapor movement I would not want it behind the drywall. Remove the house wrap and it will dry out and you will be assured it is dry.

    The Airkrete is like foam insualtion in that it fills voids and sets up to prevent air flow. So the house wrap is not being utalized as the air barrier and is not needed as a vapor barrier. If you are looking for a better interior air barrier you want to look at the air tight drywall approach.

  17. Chris | | #17

    Thank you Robert. Wish the installers had told me this.

  18. Riversong | | #18

    Robert H,

    The only long-probe moisture meter I know if is a straw bale meter, but that's calibrated for straw/hay, not cementitious foam. Moisture meters work by reading the electrical conductivity of a material, so they have to be calibrated for that particular material.

    What makes more sense is to use a standard pin-type moisture meter on the drywall. It should be 15% or less.

  19. Robert Hronek | | #19

    Whoops missed that drywall is up. As Robert R has pointed out the wrap used was perforated. What that tells me is that the wrap is not vapor porous without holes. In other words it has little windows to let water out. Contrast that to something like Tyvek that lets vapor through along the full face. Think of the difference in surface area that allows potential drying.

    I think of a house with fiberglass insulation and a poly vapor barrier. Air leaks transport water vapor into the wall and the poly traps it there. Now I think of your wall. the water is already there and your wrap my be acting more like the poly/fiberglass wall than a vapor open Tyvek.

    Think of having a towel laying on a table.Now pour water on it. If left uncovered it would take a long time to dry but not to bad as long as air flow can transport the water vapor away. Now think how long it would take to dry if you took Saran wrap and with a fork poked a bunch of holes in it. Now lay the Saran over the towel and see how long it takes to dry. This sounds a lot like your wall.

    I think you have the right idea in renting a dehumidifier. I would combine this with an electric space heater and fans. Basically I would try to suck the moisture out of all the little holes. That is going to take very dry air. When you first set up you will have suck the moisture out of the drywall. Then you will slowly start pulling the moisture from the Airkrete.

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