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Electrical Installation in Straw-Bale Walls
Wire. Electrical wires can be run in flex or rigid conduit (metallic or non-metallic), or in romex (type NM or UF), depending upon building department requirements and builder’s preferences. When romex is used, it should be buried within the bales. This is usually done by stuffing the wire between courses of bales, but sometimes involves making a groove in the straw with a hammer, bale saw, knife. In situations where lathing is tied through the bales, creating the possibility of wire being nicked in the process, we require that UF romex be used. When flex conduit is used, a shallow groove is usually made with the claw of a hammer.
Layout. The typical bale wall section, which involves a box beam at the top of the bales, makes running wire or conduit through the building a little more difficult than conventional top plate stud construction. It's often easier to run feeds and home runs in the slab or under the bale wall. Sub panels are typically located in stud walls so that wires can easily be fed to them.
Setting Boxes. Boxes are typically screwed to 2x2 stakes driven into the bales; there is also a handy sheet metal plate used for setting receptacles in steel stud construction. We typically use 4x4 metal boxes with plaster rings, and notch the straw to receive the boxes. We will set all boxes in bale walls. The electrician supplies boxes and plaster rings. Panel boxes are typically located on stud walls or screwed to plywood which has been tied to the bales.
Light Fixtures and Trim. Care in setting boxes for plaster must be taken to assure that plaster around fixture and cover plates is flat and that the plaster ring is the correct depth and is square and level. We will make a final adjustment for the depth of the box just before plaster is applied.
Wall Penetration. Penetrations through bale walls can usually be made by drilling with a long bit, and then inserting a piece of conduit to carry the wire. Care should be taken that the conduit is an appropriate length for the plaster to be applied, and it is important that exterior penetrations are be thoroughly weather sealed.