Assessing Moisture in a Straw Bale Wall & How To Deal With It
The most common time we’re asked about how to identify moisture issues is when someone buys an existing straw bale house.
Don’t worry! Moisture is not often a problem in straw bale homes as long as the house is built well.
That said, issues may show up over time and in knowing these basics, you’ll be able to spot issues early on, whether there has been unexpected roof damage or you are assessing a built home to determine the quality of workmanship.
Assessment Considerations
Moisture damage in a wall below a window.
Here are some basic things to consider when assessing moisture in a straw bale wall.
Look around the windows' lower corners for signs of moisture damage. This is the most common area where moisture damage occurs. Check inside and out in this area. You'll see staining on the plaster, or worse, buckling and peeling plaster.
Anywhere there is a wall penetration in the plaster (electrical plugs are the most obvious), take a strong sniff to smell and see if you get a hint of dampness. In most cases, you won't.
Did you locate a suspicious area?
Mold growth on a water damaged bale exposed to rain over a long period of time.
If you believe there is moisture damage, the best thing to do is drill some small holes in the plaster in the suspect areas and insert the probe of a moisture meter. Our favorite meter brand is Delmhorst. (paid link)
Any readings over 20% are concerning, as those levels can sustain mold growth. We would want to see readings around 12% or lower.
You Found Moisture In Your Straw Bale Wall. Now What?!
Oh no! The biggest fear that every straw bale homeowner just came true! You smell mold. You think your bales are getting wet. You’re getting high moisture readings on your in-place sensors. What do you do now?
Stop the Moisture
Well, the first thing, after you take 5 calming breaths is to take a step back and find the cause of the moisture infiltration. Once identified, determine the best solution to fix the issue. Without that, anything else you do will be a waste of time.
Now that the problem has been fixed to stop more moisture from coming into your straw bale wall, it is time to get the moisture out of the bale walls.
Begin Drying Out
Depending on the extent of the damage, you will have options to choose from:
Let the bales sit on their own and see how they do. If the moisture was not excessive, they may dry out on their own over time.
If that does not work, you may need to drill some 1 1/2″ holes on the interior wall about every 2′ on center in both directions. Place a couple of fans and a heater near the holes and drive hot, dry air into the wall. This will move the moisture out.
If this does not cure the problem AND the outside air is not moisture-laden, you may have extensive damage and need to gut that wall section. This is rare, and in most cases, the holes with the fans are the most extreme fix necessary.
Again, the key is to find the source of the problem quickly and fix it to prevent the continued introduction of moisture into the bale wall. Everything depends on that!
-Timbo & Dainella
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