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How NOT to Plaster a Wall: Avoid Cold Joints Whenever Possible

It's not unusual for people to get excited about plastering their straw bale structure. After all, this is when a simple structure starts to look like a home. When the plaster goes on, suddenly, the building gets a new lease on life and it really begins to feel like completion is near. This is also a very difficult aspect of the construction process and one that will be very visible for the life of your home.

When people come to visit, the plaster is likely the first thing they will notice about the home. It will either look great and wow them, or it won't. Of course, you're likely hoping for the wow factor! Okay, back to my point. Take a look at the photo above. What problems do you see? I see one major problem that happens far too often.

The plaster has been applied by several different people and there are a series of wet edges all drying at once. Here's the biggest problem: this picture was taken during a lunch break and so the "wet edges" were left to dry for a while. These dried edges will ultimately result in cold joints, areas where plaster of different wetness is in contact. The fresh, wet plaster will not fully bond to the drying plaster shown here and a cold joint will result. That's not a huge deal in this case because we're looking at a scratch coat and cold joints are common throughout the field on scratch coats. That said, it is always best to limit the cold joints in your scratch coat as best you can.

People plastering a straw bale house

As you can see in the picture above, working with lots of plastering hands is easy to accomplish while keeping a wet edge. Each person simply sets up near each other and works from the bottom up (or top down if you prefer) so that they overlap on the edges. Section by section, the wall is completed with a constant wet edge in contact with a wet edge. Should you break for lunch or some other reason, it's best to stop in a straight line that will be located differently in each coat.

In other words, don't always stop 1' from the ceiling when you take a break as the cold joints will then travel through all of the coats in which you stop in that location. You can imagine though that if this crew stopped for lunch now, their cold joint would be much more manageable than the one shown in the first picture.

-Andrew Morrison

If you're interested in really learning how to build with bales and you want to have perhaps one of the best weeks of your life in the process, then come to one of our workshops. We ALWAYS have a good time and you will gain the confidence to build your own house too. CLICK HERE to see what workshop locations and dates we have available this year!