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Any great ideas for protecting conditioned crawl from moisture during construction?

7CmVEdDP9e | Posted in Green Building Techniques on

I am building a house with conditioned crawl in Richmond VA. The conditioned crawl will be drier/healthier/more efficient once sealed and conditioned, but would seem to be wetter during construction until the air conditioner can finally be turned on.

Does anyone have any tips on sequencing construction steps, temporary protection measures, etc., so the conditioned crawl doesn’t begin life with an initial moisture penalty?

Thank you.

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  1. GBA Editor
    Martin Holladay | | #1

    Frame the house quickly, and get it dried in as fast as possible. If the crawl gets flooded, rent a gasoline-powered trash pump and empty it out. Then install a portable dehumidifier in the crawl and run the dehumidifier for a few months until the humidity stabilizes.

  2. user-659915 | | #2

    In new construction we usually get the foundation wall insulation and ground membrane in place before the floor plate goes on (it's much faster and easier to do a first class job that way). Construction moisture in the foundation wall can then only move to the exterior: any water that comes inside the crawl space before dry-in goes straight to a daylight drain, there should be nothing on the interior of the crawl space that can retain or absorb it. The drain is essential, with a sump pump if necessary but by gravity wherever possible. There should be no scenario where crawl space flooding can occur short of a major neighborhood flood. There may be a small pocket or two of liquid water where through less-than-perfect grading the membrane does not flow evenly to the drain. If this happens just mop it up with a rag before turning on the a/c.


    Our company owns several of the small portable de-humidifiers you can buy for less than $200 at the big box stores. they have adapters to connect them to garden hose and we just set them in there as soon as the roof is on and get everything dried out. Sometimes we'll put a small fan in there to circulate the dry air to the extremities of the crawl. Sometimes we have to set the unit on a coupe of cinder blocks to get gravity feed from the drain to the exterior. We do own a mud pump for drying footings when they catch rain but generally any bulk moisture is drained as James Morgan explained previously.

  4. 7CmVEdDP9e | | #4

    James, Martin, Michael:

    I appreciate the responses--we are essentially following the approaches suggested. Let's assume that before the roof goes on and de-humidification can take place, some surface mold may start to grow on the floor joists and subflooring. Once we are conditioned appropriately, this growth should stop. Is it necessary to "remediate"/clean the small amount of dormant mold, or is it frankly better/healthier to let sleeping dogs lie (again, presuming appropriate conditioning thereafter...RH has been brought below 50%, vapor-barrier in place, etc.)

    Thanks again.

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