Repairing Straw Bale Water Damaged Walls

water damaged wallsRepairing water damaged walls in straw bale is a skill that is not required very often, especially in well built homes. If it does though, it’s important to know how to recognize it and how to fix it. Below is a series of steps to consider wen dealing with water damaged walls.

Identify the problem exists. I have heard from several home owners over the years who were worried that their bale walls were rotting because they were convinced they could smell mold. In most of those cases, it turns out the mold they were smelling was from bales that were over wet during the plastering process. As soon as the plaster fully dried out, the smell disappeared, never to return. It is important that you don’t take huge steps towards fixing a problem that doesn’t exist.

Locate the problem. If you are certain that there is in fact a problem, you will need to identify where it is and how far the damage has spread. Keep in mind that bales are like sponges and will pull water and moisture into them even from fair distances. Use a moisture meter to locate the extent of the damage.

Minimize initial plaster damage. When checking for the extent of the problem, do your best to avoid ruining the plaster. After all, you may have moved beyond the extent of the damage in the bales, so why create more problems for yourself in the plaster work? Utilize the access through electrical boxes to probe with your meter. If you need to drill holes in the plaster, make them just barely big enough for the meter’s probe to fit through.

Remedy the cause. There is no point in replacing bales or trying to mitigate moisture issues if the source of the moisture is allowed to continue adding moisture to the walls. You have to identify the problem and fix it so that no new water/moisture can be introduced into the walls. The most common sources of water/moisture intrusion are broken pipes (water isolation boxes and walls eliminate 99% of these issues so please use them), roof leaks, and window and door leaks as a result of improper flashing details.

Scale your repair. There is no need to tear open a beautifully plastered wall if the moisture levels are not that high. If values are only slightly elevated (8%-12% moisture content is ideal; however, anything up to 15% is ultimately okay. Values between 15% and 20% are slightly elevated. Sustained values above 20% need more immediate and aggressive attention as mold growth can exist at this level. For lower values, drill holes in the walls and pump in warm/dry air as shown in the photo above. For worse situations, start with the warm air and monitor the levels. If they do not drop, then more aggressive action will be required, including opening up the walls.

Remove rot. If you have rotten bales due to extensive water damage, then those bales must be removed and replaced. This is hard work, but not as bad as you might think. No water damage repair is fun in a bale or conventional house. Bear down and get into it. It will be over before you know it.

Repair the holes, no matter what the size. Once the bales in the wall are fully repaired or replaced, the plaster will need to be repaired. If you only needed to drill air inlet holes, those too will need to be patched.  With larger holes, those required for replacing bales, be sure to leave roughly 6″ of mesh exposed beyond the removed plaster so that when you replace the new mesh, it overlaps and can be tied into the rest of the wall mesh. Plaster the repair and then skim coat the whole wall to blend everything together.

The good news is that you will likely never have to deal with repairing water damaged straw bale walls. The key is to build your house well from the start and to consider the most common points of entry for water from the start. Pay special attention to window and door openings and how they are framed and flashed. Be careful with roof assemblies and make sure they are properly sealed.

Do not over water your walls during plastering and be careful not to start your plaster during or right before the wet season in your area. Keep in mind that any water you place on/in the walls during plastering will need to escape into the environment and the only way it can do that is if the environment is drier than the walls. Otherwise, that water will stay in the walls until the weather clears enough for it to escape.

Have you ever had to deal with damage in your bale walls? If so, what did you do about it? Did you hire out the repair work or take it on yourself? I hope you’ll share your story below in the comments so that you can help others learn from your experience. You may think that comments are just for fun, but they actually help a lot of people make important decisions. I hope you will help out your fellow balers with your own story.

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15 Responses to Repairing Straw Bale Water Damaged Walls

  1. Avatar
    Jan Tue, October 14, 2014 at 9:16 pm #

    Thanks for the information. I am guessing we are good on ours but nice to know it can be fixed.

  2. Avatar
    kirsten Wed, October 22, 2014 at 6:20 pm #

    My hubby and i are considering purchasing a straw built home. I am a property adjuster so am inharently always looking at potential problems. I can quickly spot signs of water damage in a traditional built home, what should i be looking for in a strawbale home. I am in Northern MN. The home has a steel roof with good size overhang and a lot of windows for passive solar. Any info would be great thanks!

  3. Andrew
    Andrew Thu, October 23, 2014 at 4:56 pm #

    Hi Kirsten. I would recommend looking for any discoloration in the plaster, especially in areas where water might be an obvious issue (around and under windows, doors, hose bibs, etc.). You can also use a Delmhurst bale moisture meter to check the moisture content of the bales by poking it through the back of electrical boxes into the straw. Be sure to turn off the power before you do this.

  4. Avatar
    Barb Durham Sun, November 2, 2014 at 8:16 am #

    We’re now repairing the SECOND wall beneath a dripping air conditioner in a window. You’d have thought we’d have learned after the first one…

    The entire wall below the window became saturated and collapsed. They’re replacing the sodden, rotten bales with concrete block.

  5. Andrew
    Andrew Sun, November 2, 2014 at 10:42 am #

    What a bummer! I’d think the AC unit might need to be replaced as well!

  6. Avatar
    Barb Durham Tue, November 4, 2014 at 7:30 am #

    We’ll be getting something called a Mini-Split before next summer. Everyone but me knows what that is, apparently…

  7. Andrew
    Andrew Tue, November 4, 2014 at 6:37 pm #

    Simply put, a mini split is a ductless AC or Heat Pump system. They are typically very efficient and perfect for smaller spaces (especially).

  8. Avatar
    Lon Anderson Fri, April 17, 2015 at 1:35 pm #

    After smelling straw and taking moisture readings, we have stripped back the stucco to find an area that has been subjected to water off a nearby roof overhang. !st order to come is find the problem leakspot. The off-colored straw has been pulled out to the point of healthy straw. We plan to let this area breathe and dry out for a while in our dry Arizona spring. Here is my question: to fill the voids created by straw removal which may only be 6″x6″ and in a vertical cut (following the problem drip line), I was thinking of using expanding spray foam then lath, then stucco. Any foreseeable problems with this idea? We built our SB 15 yrs. ago and have had no problems other than some fine cracking and we love it still. Thank you for responding
    Lon Anderson

  9. Andrew Morrison
    Andrew Morrison Sun, June 7, 2015 at 9:52 am #

    Hi Lon. That should work just fine. Be sure to overlap the lath onto the existing straw/lath so that you don’t get cracks along the repair line. You could also use straw and burlap, then covered in lath, for a less environmentally impactful repair.

  10. Avatar
    Marg swafford Tue, March 22, 2016 at 6:08 pm #

    Good info. I am looking to buy a small straw bale home in Ohio. Owners purchased it a few years ago and do not have much info on it. No plans. They did not live in it for two years but had someone paint outside with proper paint. I am having hard time finding inspector with right moisture meter. Can I buy one and do this myself? Is checking behind the electrical box enough? There is walkway around the house under large overhangs . West comer of the house the walk way is tilted in toward house. I know this would have to be fixed. Should I make sure and get reading of the bales in that corner. Have not ask sellers if they will let me yet. Marg

  11. Andrew Morrison
    Andrew Morrison Wed, March 23, 2016 at 8:45 am #

    Hi Marg. You can buy a moisture meter for about $250 or so. Here’s a link to the one I use. I would get readings below every window if there are plugs there, and in any area that might be subject to excess moisture. If you want to get areas without plugs and switches, then you have to drill holes which would than have to be repaired. Often, sellers are not excited about this, but it is worth asking. I believe you would need a 3/4″ hole to insert the meter. If they painted the exterior with latex or oil paint (standard paint) then there could be some moisture issues in the wall depending on the climate, as that paint would lock down the ability for the wall to “exhale.” If they painted the interior with the same or less permeable paint, then you would likely be fine. Those general moisture levels would be prevalent in the straw behind the switches and plugs. Good luck!

  12. Avatar
    mark Tue, November 27, 2018 at 3:59 pm #

    Hi, We are in the process of purchasing a straw bale house, we recognize that this house needs a fair bit of work especially fixing up some of the walls and render. There are a number of large holes in the render and straw bale where birds have made nests. especially around the corners where the wall meets the roof. What method would you recommend to fix these holes?

  13. Avatar
    John Fri, November 30, 2018 at 7:58 pm #

    Hi ,
    I have repaired water damage strawbale walls.In a rear wall of a studio where the soil had built up beside the wall and a leaking roof gutter existed, obviously bad building maintenance ..
    The walls were clay render/plaster and suffered weather damage also but the soil built up was the real issue . Only the bottom course was affected and I was able to pull the composted straw out put in some timber struts to hold up the bales above yet they seemed to hold up without support.
    I let it dry a week in dry warm weather then stuffed straw back in and lime rendered over.

    I am pretty sure the clay helped minimised damage ,the hardwood bottom plates were in good condition . And I believe that situation in standard building materials would have been harder to repair .Even though water ran onto the floor inside the building ,the internal clay walls did not need any repair ,they remained intact.
    Now I have a job where a patch of strawbale wall was flooded by an overflowing gutter in an extreme rainstorm . It is under construction and some plastic protection in place for rendering cause the water to hit the wall.
    It had a dry first coat of lime on the wall fairly thick.
    My business partner thinks the lime will help pull the moisture out. I think taking the lime off will help it dry faster. At the moment it is warm and dry,but that wall dosent get sun (Australian south side ).
    The wet area is only the bottom half of a 12 foot wall and 1 1/2 feet wide.
    What do you think ?

  14. Andrew Morrison
    Andrew Morrison Wed, April 24, 2019 at 12:28 pm #

    Hi John. Sorry for the delay. This message was stuck in my system. It’s hard to know just how much water got into the wall, but if it was just one rainstorm, the chances re good that it will dry out even with the lime in place. I would monitor it for a while and see if the levels drop. Being that the surface of the wall is what was wet, it’s very probable that there is not actually any damage to the wall in reality. I’m curious to know what your results are as you move forward.

  15. Andrew Morrison
    Andrew Morrison Wed, April 24, 2019 at 1:00 pm #

    Hi Mark. The repair will depend on the type of plaster to some extent. In general, you will want take the following steps, regardless of the plaster type.
    1. Remove any loose plaster. Remove it farther back than any mesh you may wish to replace, by at least 6″ in each direction so that you can
    overlap new mesh onto the old mesh.
    2. Remove the mesh to gain access to the straw, assuming you will need to replace some damaged straw.
    3. Use a moisture meter to determine the moisture content of the bales. Remove any straw that is higher tan 20% or otherwise looks damaged by its
    exposure. You may have to chase this down as the moisture levels may have increased around or below the opening.
    4. Add fresh straw to the hole and pack it with a light clay slip so that it stays in place.
    5. Replace the mesh, overlapping it onto the old mesh by at least 6″. Secure with landscape pins long enough to reach the intact bales behind the
    holes.
    6. Add plaster to the holes to seal them up.
    7. Complete a skim coat of plaster over the wall to hide the patches.

    Hope this helps.

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