Baling with jumbo bales, by which I mean the REALLY large bales that require pretty substantial machinery to place, is possible. However, there are multiple considerations that need to be addressed to determine if the extra cost in foundation materials, plaster and roofing materials make it worthwhile. In this Straw Bale Minute, I address each of them.
Archive for the ‘Bale Types’ Category
This article is reprinted with kind permission from the Oak Hill Homestead blog. They cut and bale their hay by hand. One could modify the size and application of the baler to bale straw by hand. This solution could work very well in areas where mechanical balers are not available.
We don’t own a tractor, so we cut and bale our hay by hand. Last year, we stored it loose in several sheds and anywhere we could find a few square feet of dry storage space. This year, we have a hand baler. A friend in Texas sent us a link and Hubby set to work on it. The baler in the plans is for use in making a bale of pine straw, but it works just fine baling our mixed-grass hay. (more…)
It’s not unusual to end up with extra bales after building a straw bale house. In fact, I recommend it. Those extra bales are great to have around as steps or scaffolding supports when plastering. Furthermore, I would always rather have a few too many bales than not enough when building. The question is, what to do with the extra bales when the project is done?
If you live on a big piece of land, you can spread the bales out as mulch in your garden, bedding for chickens or other livestock, or simply to decay back into the soil. If you don’t have a spread of land big enough to accomplish that, you can try and find someone who does and offer them the bales either for a price or for free. This is also a great idea (either of those two ideas) for the loose straw created during construction. Believe me, there will be lots!
Another great way to use the bales if you dont have that room to spread them out is as a gardening tool. Straw Bale Gardening is a good way to grow plants in limited space, or if you have poor soil. It also helps if you have a hard time bending over as the bales lift the plants 18″ or so off of the ground. If you just finished building your own house, the idea of not having to bend over to harvest your lettuce may sound pretty good! Anyway, there are some good advantages to using straw bale gardening techniques, not the least of which is that you will use your excess bales in a healthy, positive way. Here’s a good website to get you started on this process. Enjoy!
That’s a question that I have been asked potentially thousands of times over the years teaching workshops. I like that people ask the question, actually, because it shows me that they are paying attention to the details and wanting to make the house the best it can be. The answer is usually “yes” but has been “no” a few times. When it comes to stuffing loose straw in the wall, one might think it’s easy: just grab whatever loose straw is around you and shove it into the hole that needs to be filled. Well, nope. Like so many things in life it’s a little more detailed than how it first appears.
The first thing to keep in mind is that you want to use long straw, not short and stubby pieces. Certainly do not use material that has been cut from the wall either by a chainsaw or weed whacker. That straw is way too short and will not create a solid patch.
Second, be sure to twist the straw into a rope. In fact, I prefer to twist the straw into a rope and then fold that rope in half before I place it in the wall. This helps tie it all together and keep it tight in the gap it’s filling. Spaces that can’t be filled in this way because they are too small can be filled with looser straw packed in tight around these ropes. Be sure to use long straw!
A third detail is when to use a clay slip. Most gaps can be stuffed with dry straw as long as it is well packed as described above. Some bigger holes may require a clay slip to be applied to the patch straw to help it stick, literally, in place. The slip also cuts down on potential burning of the patch should a fire spread across the wall. Of course, that’s a bummer no matter what, but it’s still important to build to the best standards you can.
Once thing to keep in mind is that stuffing the gaps between the bales, if any, is easiest done while stacking the bales. Stuff some material as described above in between the bales and pack it in tight. This keeps the stuffing in place when weed whacking and helps to tighten up the wall as you build. Waiting until after the walls are up makes the stuffing process slower and more labor intensive overall.
Several of you have, over the years, written to me about using straw bales that are wrapped in plastic. The suggested benefits of this have ranged from no need for additional vapor barrier, to ease of stacking, to being able to mortar the blocks together. Although this would seem like a good idea at initial glance, I don’t like the concept. Here’s my thinking:
Photo Credit: www.wajking.com.au
One of the most important aspects of straw bale construction is the ability for the walls to move moisture through them. I’m not talking about water, per se, but moisture in the form of vapor. The fact of the matter is that vapor will be present in your house and that moisture will find its way into your walls. What if you shower and forget to turn on the fan? Where does that moisture go? What if you forgot to turn the kitchen fan on while boiling a pot of spaghetti? That moisture has to go somewhere too.
Moisture collected or formed in the house (think about breathing house plants) will be pushed through the walls by the pressure of the home. Again, this is just reality: that homes are pressurized. Notice when you close an interior door that has a tight fit or when your bathroom fan turns on and slams your door the last 1/2″. That’s the pressure I’m talking about. If the bales are wrapped in plastic, there is no way for that moisture to get out. It WILL find its way through at whatever cost. That may mean finding a small penetration in the plastic and getting into the bales…only to find it can’t get out the other side. Now you have a plastic wrapped box of mush!
Another advantage of bale construction is the fantastic bond that is made between the plaster and the bales themselves. If the bales are wrapped in plastic, that bond cannot exist and so the overall wall assembly is weakened. Not much more to say here. I think that’s pretty clear.
The advantages, or potential advantages of using plastic wrapped bales are far outweighed, in my opinion, by the risks that such a process would create. I suggest you stick with the bales in their natural state.
1. Long straw. Be sure to ask your source is the bales are long straw or chopped/thrashed straw. A bale harvested by a combine will be thrashed straw and the short pieces make for a very weak bale. These are a poor choice for building. A long straw bale will typically be 14″ tall (2-string) and 16″ tall (3 string).
2. Look for a cut edge and a folded edge. If the cut edge is not clearly visible on one SIDE of the bale, it is probably a thrashed bale and the “cut edge” is likely facing up or down. Again, don’t buy these bales.
3. Color. You want a bright, golden color. Brown or black bales have seen moisture damage. Dull bales may have been stored for a season or longer. They can be acceptable if the other details check out; however, fresh bales are best if you can find them.
4. Moisture Content. Bales should be around 8-13% moisture content when checked with a bale probe. Under no circumstances should the bales reach higher than 20%. At that level, mold growth is supported.
5.Density. The easiest test is to pick up a bale by one string. If the bale deforms in any way, then don’t buy the bales. If the bale stays completely in shape, then the density is acceptable.
6. Shape. tight, rectangular bales are what you want. check the corners of the bales to make sure they are not rounded. Rounded corners will mean a lot of stuffing after the wall is stacked. Tight, angular corners mean the bales will fit together well and your stuffing will be limited.
7. Smell. This is another test of moisture. When you walk into the barn, take a deep inhalation through your nose. How does the room smell? Musty is not a good sign. Fresh straw is what you want to smell.
8. Weight. Dry bales will be relatively light weight. A 2-string bale should not wiehg more than say 45lbs. If it’s heavy (you’ll know what heavy means when you feel it) the bale is probably wet.
Most importantly, use your common sense. If something seems off, it probably is. The importance of quality bales can’t be stressed enough. If you get bad bales, you will fight them from the moment they arrive on site to the moment you finish the house. They make for more retying, more stuffing, more material loss, more post stacking compression, less effectiveness of wall clean up (string trimmer work), weaker vertical stands and corners, more tamping to get your walls plumb, weaker plaster substrate and more. Trust me, get quality bales.
Happy (quality) baling!
Why would I want to do that? You may be asking yourself that very question and rightfully so. The answer may be simple or complicated depending on the situation. It may be that you have a series of wall sections that need thinner bales than the rest of the house due to framing and engineering requirements. One place where this is common is at the top of the wall system. It’s not unlikely to have a large beam at the top of the wall supporting the roof. That beam, hopefully a 4x something, will not allow you to reach the outside face of the wall with the plane of the bale and you’ll have an entire section of bales that’s 4″ too wide at the top of the wall. In some scenarios, you can simply turn a bale on edge and it will fit perfectly. In others, you can’t. I’m not a huge fan of using lots of loose stuffing in the house to fill larger voids like this. I think that starts to weaken the wall in the end. In fact, the tight fit of the bales to the top plate is one of the ingredients for a tight and solid wall. By cutting down regular bales by the required 4″ (in the scenario described above) you can install regular bales, stay with the running bond pattern, and install them tight to the top plate. Only minimal stuffing will be required.
Here’s another scenario that a friend of mine just experienced. Because of his location, he had to have his bales trucked in from another state. That’s not ideal, as I prefer to purchase bales locally, but he wasn’t able to do that due to current local straw stocks. Having installed his toe ups, and framed the house, he was ready for his bale delivery and it showed up right on schedule. Only one problem…the farmer sent him three string bales, not the two stringers he had ordered. The three string bales were 6″ too wide for the house he had built. He thought about stacking them on edge and I was able to talk him out of that. When he asked me for suggestions of what to do, I contacted a friend of mine with a portable sawmill. Here’s a scenario where he had to trim 6″ off of 400 bales and do it quickly. Every day that he didn’t have bales to install, the job was falling behind schedule.
So with two laborers and one sawmill expert, the entire stack of 400 bales was cut down by 6″ in a little less than 6 hours. If you’ve taken a workshop with me, watched my DVDs or just paid close attention to bales in the field, you’ll already know that a standard straw bale has two edges: a folded edge and a cut edge. That’s due to the way a baling machine works, folding the straw into the chute with a plunger, tying the bale and then slicing off one edge to make the bale the right size. I always recommend that the bales be stacked all the same direction in the walls, cut side in or cut side out. There are some factors that do into deciding which way to face the bales, but that’s not the point of this story. In this scenario, the “new” cut edge was extremely clean and sharp. It made for the perfect interior wall surface as finalizing the wall clean up will be easy with the pre-cut bales all facing the same way. You can see in the picture here how nice the bales turned out and why they create a clean surface for the interior wall.
Although I really don’t recommend planning on the use of a portable sawmill unless entirely necessary, it’s good to know that they work so well and so quickly should you find yourself in a similar situation. The best remedy for this problem is proper planning and proper communication. Mistakes get made, it’s part of life, and so having a back up plan to great planning and communication is a good thing.
There are so many reasons why I suggest you not build your house with the straw bales on edge. It’s hard to know where to start. I’ll just lay out the first ten that come to mind.
1. Strings on the exposed face mean no notching around posts and thus a thermal break at each post.
2. Bales are not sturdy. If you throw a bale off the stack it will land on the flat 99 out of 100 times, not on edge.
3. Any framing in the wall eliminates the running bond system, thus weakening the walls.
4. No weedwacking is possible to smooth the walls.
5. Running electrical is difficult because you have to cut chainsaw grooves around strings.
6. Corners are unsupported because you can’t notch the bales around the posts, therefore there is no overlap.
7. Niche construction means cutting the strings and weakening the wall.
8. The shape of the bales requires more stuffing when on edge.
9. The exposed surface of the bale has less “tooth” for plaster than when the bales are stacked on the flat.
10. Wall settling may be more as the strength of the straw bale is not from side to side but from top to bottom.
Having worked with bales on edge on several occasions, I’m certain that I won’t do it again (if I have control of the project). The only reason I’ve heard as to why people think it’s a good idea and continue to do it is that it saves square footage because the bales are thinner in the walls this way. Let’s be realistic, you only save 4″ per wall and that’s not worth it in my opinion. If you plan to build with bales, you need to know that your walls will be thick. If that’s a problem for you, there are other building systems out there to consider or you can use a portable sawmill to rip your bales down by 4″ and then use them on the flat. That’s not ideal, but better than stacking on edge. I’ll write more about that process later.
If you plan to build with bales, you absolutely must have a moisture meter with a probe. It is so valuable that I consider it a “must have,” not a “it would be cool to have” tool.
Use the meter to check the moisture levels of bales before you buy them. I randomly check about 10-15 bales in a stack to see what the moisture levels are. Be sure to check the side of the stack and the top as moisture can get in either direction. Insert the probe all the way into the center of the bale as moisture in the center is almost impossible to drive out whereas some surface water on the sides of the bales can be eliminated quite easily.
You can also use the meter on site. There may be some suspect bales in the delivery you receive and rather than take a chance on installing a wet bale, the meter will allow you to check the moisture levels on the spot and make an informed decision. I keep my meter on site during every job.
Here’s a link to the meter I use. You can buy a meter like this one factory direct, or you can find them in farm supply stores. It doesn’t matter where you go to get it, just be sure you actually buy one!
What is the perfect bale to use in a straw bale house? I am asked this question a lot. Most times, the question refers to what type of straw is the best. Some people say rice, others say wheat. I always tell people to buy what is most local as long as it is dense, dry, and clean. The other side of this question is in relation to the size of the bales to be used. Many people want to know if a 2 string bale is better than a 3 string bale for home construction.
Once again, I believe the best bales are those most local to your construction site. In general, most farmers are moving towards bigger bales and so that will have an impact on what you can find in your area. Three string bales stack more easily in the field and are more stable when moved by a squeeze (farm machine that moves large blocks of bales). For that reason, more 3 string bales are available today than 2 string, in most markets. So, first concept: buy local.
Here’s the advantage for two string bales: they are easier to work with. They are lighter, smaller, and generally easier to work with than 3 string bales. I prefer two string because I can handle the bales by myself whereas three string bales take two people to move and stack, especially after a long day of baling. The R-value on a 2 string bale is less than a 3 string bale; however, it is already so high, that the difference is not that noticeable. Unless you live in a VERY harsh climate (either hot or cold) the difference between 2 and 3 string bales will be hard to notice.
The advantage of 3 string bales is that they are more solid when stacked. As mentioned above in the field stacking ability of 3 string bales, they are very sturdy because of their larger base surface area. This translates into strong walls as well. I prefer 3 String bales when building load bearing for just this reason. In addition, because they are wider, you can cut deeper niche into them which is also a nice feature.
The reality is that both 2 string and 3 string bales have their advantages. See what is available to you locally and then decide which advantages best lines up with your plans to build. You may find that it really doesn’t matter to you which size you use. In which case, stick with the local kind.
I received the following comment on my old blog. It started me thinking about rice straw and humid climates and I noticed that many of the humid climates are actually where rice grows and thrives. To that end, I wondered if it might really be possible to build with bales in a humid climate if the bales were rice straw. I am not in a position to undertake this study, but want to present a challenge to you all:
Are you willing to do the unbiased research to see how rice straw holds up under humid conditions? This will need to be a scientific experiment to hold mustard with critics. If you are interested, please let me know. Perhaps we can get some funding to do the research if your proposal is strong. I am excited about this chance to expand the world of straw bale construction.
Here’s what the blogger had to say.
Andrew, I just happened to run across this post and comment section as I was searching through various alternative construction sites. I am not an expert in any shape or form on any of these methods but I noticed the questions from the people in Southeast Asia about bale construction there .
One of the sites on materials I was looking at on my earlier searches for information made the claim that rice straw takes twice as long to decompose as wheat straw because of the higher silica content .
Whether this is true or not I cannot say. I simply wanted to pass the information along so others working in these areas might be alerted to check further on whether or not this is indeed true. If it is it might positively effect the viability of straw bale construction in more humid areas that have access to inexpensive rice straw .
There is a new website out there that helps people find straw bales all over the united States. They can deliver as well and have a price break for those buying in bulk. The website is very well designed and I hope will prove to be a great asset to us bale builders and home owners looking to build with bales.
The site is called, funnily enough, www.StrawSale.com. I guess that is a good indication that strawbale.com has continued to influence the world of bale construction! So check it out and good luck finding the right bales near you.
For years now I have been using a weedwhacker to smooth the walls of every straw bale house I have built. But no more! From now on, I plan to use this cool invention created at my last workshop here in Jacksonville.
Here’s the history. Several workshops ago, a man name Frank came up with a cool little rasp made out of blood lath and a piece of 2×4. He used it to clean up the straw in the back of the niche he had created in the wall. It worked very well and then when I presented the idea to several workshop participants at the September workshop, a couple guys took the idea and ran. In the picture above you can see the little rasp has turned into a full size tool! By using a long piece of 2×6 and a section of blood lath, Ryan and Will made a full size rasp that cleaned the walls better than any weedwhacker and many times faster!
The coolest thing about the rasp is that it is long enough to create a flat wall using the posts and window framing as a guide. A little shaking and shimmying and the wall is clean! Thanks to Frank, Ryan and Will for their great ideas. It has changed how I clean bale walls for sure.
When you make yours, be sure to fold the edges of the blood lath over so no cut ends are exposed. The cut ends can rip you up. Ryan mentioned using leather around the edges to wrap the lath safely. Handles on the back of the 2×6 were made out of scrap 2×4, but a better, long term design would incorporate more comfortable handles. Have fun!
When building a straw bale house, the bales are likely delivered to the site in squeeze blocks: tall 8′ x 8′ blocks of straw bales. Here’s a simple solution for getting the bales from the top of the delivered pile to the ground where you can handle them. In most cases, people climb their way to the top of the pile and then throw the bales off to the ground. This will usually damage at least some of the bales and is a good way to squish one or more of your generous helpers! There is a better way.
To safely get your straw bales to the ground, use two long sections of 2×12 framing lumber. Place the leading end of the 2×12′s on the top course of bales far enough apart to fully support the width of the bales. One at a time, slide the bales down to waiting hands on the ground. This will allow you to quickly and safely deliver bales to the bottom of the stack without deforming or destroying any bales or friends!
When you are done with each course of bales, move the 2×12′s down to the next level and continue with the unloading. The lower on the pile you get the closer to the house the end of the 2×12′s will be, which makes the day seem even easier. When you are all done unloading the bales, set the 2×12′s aside as they make excellent scaffold planks for the first story plaster job. Lay the planks across several bales and you have a long working surface that will allow you to reach the top of any standard wall height. Be sure to support the middle of the span as 2×12′s are not technically strong enough for scaffolding with an unsupported span. Remember that the planks will be longer than your pile of straw was tall.
One situation you are likely to find yourself in when building a straw bale house is the ends of bales sticking too far into a room or beyond the plumb line of an exterior wall. As you know, when you build a bale house, you interlock the corners by placing one bale East-West and then the next bale course North-South as you turn the corner. In doing so, it is easy to stack one of those bales out of plumb and not notice it until the whole wall is stacked. Another place this is common is around window and door openings. I have seen many folks terminate the bales too far into the window opening to create the shape they want when meshing and shaping. Those bales need to be cut back to allow for proper shaping.
Exactly how to fix this problem can impact the quality of your walls and the ability of those walls to anchor mesh properly when you shape corners, etc… In the past, the simplest fix was to cut the twine on the bales that were out of plumb and pull out the excess stuffing to get them back in line. This works well because the bales, once stacked tightly to the ceiling, can handle the cut twine without falling apart. The problem comes during the shaping/meshing portion of the build. When you stretch the mesh back across the bales and then landscape pin it, you are asking the bale to hold the pin; however, you are also asking the mesh to hold the bale since you cut the twine thus limiting the strength of that bale. Therefore, both cannot happen. The bale cannot hold the mesh because it will be too weak from losing the twine and the mesh cannot hold the bale without an anchor point for the pins. Oh what to do?
The answer comes from an old farm fencing trick. Have you ever looked at barbed wire fencing on an old farm? If you check out the last section, at the corners, you will often see a rotting old stick wound up in the wire. That stick is the answer. It is called an apron tie. The stick is used to twist the wire tight and then is left in place to hold the fence tight. This same concept works with bale ends. I use a bale hook to scrape away some of the straw on the ends and then pull out the rest of what I need out by hand. Then using either a stick, a piece of rebar or bamboo, or a nail, I twist the baling twine tight with the apron tie. A 20d nail works well because once it is twisted tight, you can stick the nail into the bale to hold it in place. The larger items like rebar and sticks are a bit stronger and often easier to twist, but require additional anchoring to hold them in place. If you use the larger twists then use a landscape pin to hold the tie in place.
This concept will provide really strong bales to attach the mesh to and will easily clean up those “growing corners” as I like to call them. Of course, keeping your corners plumb and in check from the start is always the best plan, but it is good to know you can fix them if they are not set up properly.
I always remind people to clear the loose straw from their job sites for several reasons. The first reason is always fire protection. The second is for slip protection. The third and new reason is for snakes!
I live in an area with rattlesnakes among other less dangerous ones. I was clearing out a bunch of loose straw today from the area below the last workshop site. In that process, I came across two snakes who were less than pleased to see me. Neither one was a rattlesnake, I was happy to see, nonetheless, I jumped a few feet when I found them. So, be sure to clear the loose straw away, especially if you live in an area with dangerous snakes!
I often talk about knowing where your bales will come from before you start building and even designing so you can know the dimensions and how those dimensions will affect your process. I cannot say how important this is, now more than ever. The number of available bales in the Northwest is so small right now, that I am struggling to find enough for my June workshop! I have contacted all of my sources and have managed to find some bales, only to run into the dilemmaFr1skyandS of how to get them here. Fuel costs being as high as they are, it is hard to cost effectively transport bales any distance.
I always support buying locally and using bales from your immediate area if possible, but sometimes that simply cannot be done. It appears that I may be in this situation myself now. Oh the irony of that huh?! Anyway, I it looks like I have found some local bales, but they are nowhere near the size I am used to using. This means that the structure I plan to use for my workshop will be unprepared for the larger bales that will show up in a couple weeks. This is ultimately a great lesson and one that I will teach the participants, first hand!
Know your source. Confirm the availability of your bales. Know the bale dimensions. Have fun. These are all important aspects of building with bales…not necessarily in that order!
Perhaps the greatest tool on a straw bale construction jobsite is the bales themselves. Of course, I LOVE the straw bale needles I use, but there is nothing quite as amazing as the many uses of straw bales on a site.
I use them as a free standing table when retying bales and notching bales, and add plywood to two bales top create a hard surface table when cutting roofing felt and other materials. They also make great ladders when stacked properly. Ever try carrying a 45 pound straw bale up a stepladder? Trust me, it is way easier to walk up a step way made of big solid bales.
It is well worth adding a few extra bales to your order for use around the jobsite. You will be happy you have them more than once during the construction of your project.
There is a good chance you will have a lot of straw left over when you complete your house. Most of it, if you did your estimating right, will be in the form of loose straw. You will be amazed at just how much loose straw is produced on a building site. As I have said earlier, this loose straw is dangerous to the site as it poses the highest fire risk of any building material on site: dry, loose piles of straw! Be sure to move it away from your structure. But what to do with it all?
The best answer is: grow things! Use the straw in your garden as mulch. Use it to plant potatoes. Use it to make compost, especially if you have chickens. In fact, use it as chicken bedding or other animal bedding. There are so many wonderful uses for the “waste straw” that it really isn’t waste at all. There are not too many building materials that can honestly claim that.
If you do not have the space to use all of the straw, I suggest you contact your local farmers. Many, especially those who grow vegetables in small scale farms, will be thrilled to have free mulch. There are also farmers who make organic compost that need straw one of many ingredients in their mixes. They too enjoy free straw. The point is, it is never wasted if you take the time to find a good home for it.
Now what about the left over bales? You might be able to sell them to someone interested in building or in need of bales for something else. If you just have a few, you can use them as planters. It’s actually pretty cool. You carve out holes in the top of the bales and plant directly in the bales. The straw keeps the roots insulated and moist and the slow breakdown of the bales provides food for the plants. In addition, the roots have free run of the place throughout the bale, making a stronger plant. When you are done and are ready to harvest the plant for the last time, you can then thrown the whole planter into the compost and begin the cycle for next year!
Of course, there are plenty of things you can do with bales which I have not discussed. Build the kids a fort. Protect areas from run off. Build a garden wall. Many options are out there. Be creative and have fun.
All too often the conversation about how to protect bales in a straw bale wall is held without any mention of how to protect those bales prior to their installation. So, how do you protect the bales once they arrive on site and before you install them? For some reason, most likely Murphy’s Law, it will rain once the bales have been delivered, even if you are building in the middle of the desert! I consider a fresh stack of dry bales to be a rain magnet.
The first thing to consider is timing. Do not have the bales on site before you are ready for them. There is no point in storing them on the job site while you are still framing or preparing for bales. They take up space and are more likely to be damaged the longer they “hang around.” Deliver the bales the same week you plan to start baling.
Place them on pallets in strategic locations. When they are delivered, immediately distribute them around the site so that you will not have to carry them around the house just to install them. It is a little extra work in the moment but will ultimately speed up the construction of your project.
Once they are distributed, cover them with quality tarps. If you live in an area prone to wind, you may need to anchor the sides of the tarps down. If, however, you don’t see much wind, it is best to leave the sides of the bale stack exposed to the air so that any moisture that builds up under the tarps can be eliminated by air circulation. It is also a good idea to stack the bales in a pyramid so that any condensation will slide down the tarp and not simply drop on to the bales.
If you have to receive the bales before you are ready to use them, find a dry spot on your land and stack all the bales in one area on top of two layers of pallets. The two layers help to keep the bottom course of bales out of the grass or away from the moisture of the ground. Stack the bales like a pyramid and cover well with quality tarps. I use “Hay Tarps” because they are big and well built. The last thing you want to do is skimp on the tarps and find your entire lot of bales get damaged by rain. Leave the sides open for air circulation as described above unless wind driven rain is in the forecast. If it is, be sure to cover the sides before it shows up!
Again, the key is to leave your bales at the source as long as possible, assuming that the source has a dry barn. If the bales will be left unprotected at the source, then you may want to have the bales delivered so you can ensure that they are protected.