If you are planning on building a straw bale home, chances are you will be including electrical services in the structure. Exactly how those services are installed is different in a straw bale home than it is in a conventional home. Knowing exactly how to install electrical service in your structure is important whether you plan to do the work yourself or hire it out to a subcontractor. You’ll either need the skills to install things properly yourself or in order to explain things to your contractor as they likely will not have worked on a straw bale house before.
It’s a lot easier to learn specific skills and building techniques in person with hands-on training, but I will do my best to describe the process to you here, step by step. Everyone loves bullet points, right?
- Know where your service panel will be located. This is usually required to be shown on the construction drawings, but nonetheless is missed sometimes. It is important to know exactly where the panel will be located for two main reasons. First, if it is located in the bale walls, you will need to create bale stops on either side of the panel location so that the straw stops against a solid surface. This ensures the bales fit tightly in the wall and that you have free access to the box to run your wires in. Secondly, you need to know where to terminate your “home runs,” the wires that run from each circuit to the panel, so that you can power each location as necessary.
- Create a game plan for your home runs. Because installing wires in the bale walls is harder than installing them in conventionally framed walls, it’s best to plan for as many home runs to be made through interior, framed partition walls. In this way, you can connect each load source (plug, switch, light, etc.) to a home run that returns to the panel as easily as possible.
- Mark you locations on the wall. I use a can of bright spray paint to mark all of my crucial locations on the bales before I start installing anything. This is a great way to locate potential problems before they arise in physical work. Be sure to mark out all of your niche locations before you start drawing electrical notes and runs on the wall. If you don’t, you may run electrical work right through the middle of a perfect (or at least what was a perfect) niche location.
- Build your mounting plates. I use a totally different system to attach my electrical boxes to the wall than most straw bale builders do. I used to use the “vampire spike” like other builders, but I have come up with a better way of doing it that creates a more solid connection to the wall. What’s even better is that the creation of the mounting plates is much safer than making spikes. The plates are made of 1/2″ plywood and should be a few inches wider on each side of the box than the electrical box itself. This usually means making 12″ x 14″ plates, or so. Cut a hole in the plate to allow the electrical box to fit snugly. Drill a hole in the upper corner big enough to allow your baling needle to fit through. You will eventually use this hole to temporarily tie the plate to the wall. Cover the plate with roofing felt and then insert the electrical box. You need to use “old work” or “remodel” boxes to work with this system.
- Create box locations on the wall. Turn the box so that the flat plate sits against the wall and spray paint its outline on the bales. You will need to use a chainsaw to cut a relief in the wall so that the plate sits flush with the plane of the wall. This means cutting just enough for the thickness of the 1/2″ plywood and then cutting a deeper hole in the bales to allow for the electrical box itself since it protrudes from the back of the plate significantly. Be sure to locate the actual electrical box at the required height. In fact, the temptation is always there to measure to and/or plumb and level to the plywood plate. Resist this temptation and make all of your measurements to the actual electrical box because that is all you will see once the plaster is in place.
- Cut grooves in the bales. Use a chainsaw to cut grooves for the wire runs. I want my wires to be no closer to the surface of the wall than 2″. This makes sure that they will never be punctured by someone hanging a picture on the wall and it surpasses code requirements for wire depth in the wall. Always cut your lines vertically or horizontally. Do not cut corners by angling your wire runs. This causes confusion in the future and can lead to someone getting hurt down the line when remodeling or otherwise working on the electrical system, as most electricians expect runs to be installed in only those two directions.
- Install your wires deep in the wall. Use a push stick to make sure the wires (direct burial wire/UF-B is acceptable for installation into the straw) are installed as deep in the wall as possible. Use 6″ – 9″ landscape pins to anchor the wires in place every 2′, at a minimum. It is important that the wires not migrate towards the surface of the wall overtime while you are completing later phases of the construction process. Once they are fully installed in the wall, stuff straw into the groove to completely cover the wires. This protects them from coming in contact with the plaster, which could destroy the casing. Leave at least 6″ of wire in the box to work with later.
- Label your wires. It may seem obvious which wire is coming and going, but it won’t be once the plaster is in place. For this reason, use a permanent marker to label the end of each wire. Simple notes such as “HOT” and “TO LIGHT” are all you need in most cases. For more complicated installations, be sure to write as much information as you think you will need later to identify each wire. Tie your plates to the bales by using a bale needle to thread baling twine through the upper hole through the wall and back. This twine will be removed later, so just tie an overhand knot to keep things in place for now.
- Use the mesh to anchor your plates. When installing your mesh, do not attach it to the plates until you are ready to lock them into final position. Measure your box heights, and use a torpedo level to make sure your electrical boxes are exactly where you want them. Holding them in position, staple the mesh to the plates. Be careful to use staples that do not penetrate through the plate as that might pierce a wire. If you must use long staples, be very aware of where your wires are located so you don’t hit them. With the stapler in hand (and I’m talking about a pneumatic stapler that shoots structural staples, by the way) attach a final plate cover made from plaster lath (diamond lath or blood lath are other names for this material). This gives the plaster something to hang onto over the plates and ensures a quality plaster job.
- Mark it up. Use your bright spray paint to outline where every electrical line is located in the wall before you plaster. Stand back and take some pictures to include in your home portfolio. This way, you will know where every wire is in the wall and you can make informed decisions should you decide to remodel later. Finally, place tape over the electrical box openings so that no plaster will find its way into the box and most importantly, into the screw holes.
Like I said, it’s easier to learn this process hands-on; however, I know that not everyone can make it to one of my seven-day workshops so I hope this was helpful in at least getting you started. Happy Baling!
About the Author
Andrew Morison is a specialist in straw bale and green construction. He has shown thousands of people how to build their own straw bale projects through his comprehensive series of instructional straw bale, concrete foundation, and plastering DVDs, as well as his hands on workshops. You can check these out at www.StrawBale.com/store.
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