How to Build a Truth Window

A truth window is a location in a straw bale home where people can view what is behind the plaster, Very often, they inspire conversations with curious visitors. Most, if not all, straw bale homes have one. Some are simple and others elaborate. The style of the window is often a reflection of the owners. Most of the truth windows I have seen or created are simple and humble.

Often, the window is no more than an 8″ x 8″ hole in the plaster. I have also seen and created truth windows that are akin to true windows, with working shutters and glass. Below is a description of how to create a simple, bull nose plaster truth window.

The first decision with any truth window is where to place it. Would you rather display it in a more public setting or private location within your home? Once you have a sense of where it will be located, consider what you will see in the window. Position the opening so that the different components that make up the wall are displayed. Show the straw, wire mesh, bamboo and whatever other materials were used.



  • For a simple, bull nose plaster window, use the plaster itself to frame the opening. Follow the directions below to accomplish this:
  • Place 2 inch masking tape on the bales in the shape of the opening you want.
  • Use the scratch coat of plaster to rough in the shape of the window.
  • Land the plaster about 1″ on the tape.
  • Allow the plaster to dry after you scratch it like the rest of the base coat.
  • When applying the brown coat, use a margin trowel to form a bull nose with the plaster as you round into the opening.
  • Once again, land the bull nose on the masking tape, keeping the straw clean.
  • Wait to float this area until the brown coat has set up quite a bit.
  • If you float it too soon, it will be difficult to maintain the shape of the bull nose.
  • Use a damp sponge float instead of a neoprene float to finish the bull nose. We are trying to find a good online supplier of these plastering tools. Until then please visit your local plaster store to purchase these.
  • After the brown coat has dried, use a razor knife to cut the tape back to the face of the plaster.
  • Use the final coat of plaster to touch up the bull nose.
  • Dive the plaster into the straw with a margin trowel to create a sharp, clean edge.


Andrew Morrison has a passion for straw bale construction that is matched only by his desire to teach his knowledge to others. He has a wealth of experience in designing and building both conventional and straw bale homes. After years of building, he has moved his practice entirely to consulting and teaching. He shares his knowledge with thousands of people via his DVD series and this website and teaches roughly six-eight hands on workshops each year. For more on his workshops, please visit  Andrew received a BA degree from Hampshire College in 1995 for Glacial Geology. He also has a degree in construction technology.

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