Keeping Your Bales Dry

Suggestions for a Grey Day

by John Swearingen

Bales are big and bulky, and are vulnerable to rain, fog and condensation until they are resting safely under your roof. A little thought about logistics and protection early on could save a lot trouble and aggravation later. Any sailor can tell you that the weather is unpredictable and any good sailor is always prepared for the worst. Bale builders should likewise be prepared. Here are some suggestions:

Before your bales even arrive, it’s wise to purchase and have ready a good tarp and plastic to cover your bales in case of a squall, a storm or other threatening weather. It’s very good insurance.

When your bales arrive, stack them where they can easily be reached when it comes time to build. We prefer to schedule our bale delivery the week of the bale raising. This saves us the time and trouble of keeping the bales dry at the building site.

We set our bales on palettes or lumber to keep them off the ground. We avoid putting plastic under the stack, because a plastic floor will hold any moisture or condensation against the bale bottoms and quickly lead to rot. If the ground is especially moist, put plastic on the ground, but keep an air space between the bales and the plastic.

For best weather protection, make the bale stack tall and narrow rather than flat and wide, minimizing the flat area exposed to sun and rain. The top of the stack can be peaked or rounded to increase water run-off. We cover bales first with large plastic sheeting, and then use tarps to protect and tie down the sheeting. Normal morning fog or condensation will not damage bales significantly, but watch for tucks or folds in the tarp which might collect the dew and dump it onto the bales, causing problems over time. If you don’t cover the sides of the stack, it’s a good idea to hold the edges of the tarp away from the sides to allow dew or rain to drip directly onto the ground.

If the bales will be stored for over a month, it’s a good idea to allow some air to circulate around the stack. We put lumber on top of the stack to hold the plastic off the straw. Sometimes the sun will heat the stack, baking moisture out of the ground and the bales. That moisture is moved by convection to the top of the stack where it will condense against the plastic. A little air gap prevents this.

If storms are predicted, lash your tarp thoroughly. We get plenty of rope and truss the bales by wrapping around and around the sides of the stack. Do not rely on weights to secure your tarp. Even a heavy boulder is no match for a flapping tarp. If the tarp can’t flip off the boulder, it will often tear itself loose in a heavy wind.

Once your bale walls have been stacked, and before the roof and plaster are on, your bales continue to be vulnerable and the cost of replacing them is much greater in time and aggravation. Replacing wet bales in a wall is not nearly as much fun as stacking dry bales.

Ok, so what if the bales are stacked and then a storm hits? If you have a small building, it may be possible to have a tarp on hand, which will cover the entire building if weather threatens. Most moisture damage comes from water entering the top of the bale wall, usually following a path made by the pins holding the top plate to the bales. A simple precaution, then, would be to lay tarpaper or plastic over the top of the bale wall and/or over the top plate. This can be a temporary cover or can be designed to be left in place when the building is finished off.

Generally the sides of a well-stacked bale wall can endure significant rain with only slight damage, but watch for conditions which would funnel and/or concentrate large quantities of water into or along the bales. These areas might occur around window openings or as the result of folds in the tarp, or could happen where wind might blow otherwise benign run-off into the bale wall. Notched-in-place posts and beams create pathways for water to enter deep into the bales. If your building has a lot of these areas, particularly on the weather side, consider draping a plastic sheet over the wall during construction.

Suppose your bales get wet, what then? Well, it depends. Wet bales eventually will dry out, but if they take a long time to dry out, some damage to the straw may occur--that is, fungi may have digested some of the straw. Opinions differ about how much to worry about this.

One school holds that once a bale has gotten wet it should be summarily thrown out. The notion is that even if very little damage has occurred, the bale is now "charged" with spores, and that any further moisture exposure will activate these spores and trigger widespread fungal growth. I believe this argument is specious. Although it never hurts to toss out a questionable bale (if you have extras), fungi are omnipresent in dry and damp bales alike, and are entirely dependent upon humidity to grow. Fungi grow when humidity is present, and don’t grow without humidity. Fungi will not spontaneously spread through a bale like multiplying bacteria unless the bale is damp.

If bales do get wet, they should be evaluated in two ways: (1) have the straw fibers been damaged by fungal activity, and (2) will the bale dry sufficiently before the building is completed? It’s pretty easy to tell if a bale is damaged--it’s likely to show some blackening, and it might smell or be warm. If you have any doubts, set the bale aside to use as a half-bale and when you open the bale up to make the custom bale you can assess the condition in the center of the bale. Given the right weather conditions, a bale might be soaked on the inside, but the outside might appear dry. A moisture probe is very useful in checking for these conditions, but you can also stick your hand between bales and feel for moisture.

Not surprisingly, bales dry faster in hot, dry weather than in cold, damp weather. A bale might dry in a couple of weeks during the summer--and never dry out during the winter. Damp edges dry quickly, but damp centers may be very slow to dry out. Small, localized areas of damp may not cause significant damage to the wall, even if the area composts before drying out. But large wet areas or widespread damp can jeopardize your building. Significant rot might occur before the bales dry, or in extreme cases extensive composting could become self-sustaining.

If a wall gets wet, but might be possible to delay plastering until the warm winds of summer have had a chance to caress your building. Bleach can be applied to reduce damage to the straw, but the bales still need to dry out. The best thing might be to locate wet bales and replace them with dry ones. This is generally not very difficult once the decision is made. After plastering, bale walls absorb moisture from the plaster, then continue to dry as weather permits. Walls have been successfully force-dried by drilling holes in the wall and forcing air through the damp bales. We had poor results blowing air through small holes, but we’ve heard of successful experiences sucking air out of a damp area and also blowing hot, dry air through bigger holes. Nevertheless, an ounce of prevention is worth pounds of hot air. Keep your tarp handy, your rope ready, and your eye on the sky.

by John Swearingen