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Trailer Undercoating - YUCK

One task that I have been putting off is waterproofing the underside of the Wicked Tiny House. Let's start with a little background. Tiny houses that are built on trailers almost always have some kind of waterproofing on the underside. This protects it from water while being towed and moisture while being lived in. Typically, before the house construction starts, some kind of impervious material is laid over the trailer frame. The most popular material is a thin layer of aluminum. Once the impervious layer is installed, floor framing is installed, typically 2x4's, followed by insulation, then the plywood/OSB subfloor, and then the rest of the house. This is NOT what the previous owner of my house did.

My house was built with a layer of OSB (oriented strand board), followed by 2x4 framing, followed by the OSB subfloor. The lower layer of OSB was placed directly on the trailer frame without the impervious layer, which means the the entire underside of the house is exposed to the elements. The previous owner should win some kind of award for cutting this corner. I knew this when I bought the house, and figured it was something I could easily solve by lifting the entire house off the trailer, installing a layer of aluminum, and setting it back down on the trailer. Well, I procrastinated, and here I am today, with a nearly finished house with an exposed underbelly.

Enter waterproofing Plan B. I decided that the easiest way to waterproof the underside of the tiny house would be to use a spray on undercoating/truck bed liner, similar to Rhino Liner. In all my searching online, I couldn't find anyone else who had used this method, likely because they all did it right the first time. Anyways, I found a good deal on four gallons of the stuff undercoating, bought a spray gun, and went to town. I learned within the first few minutes that the undercoating will stick to anything, but by then it was already covering my arms, legs, face, and hair. I remembered that I had old Tyvek suit kicking around that I previously used while riding my motorcycle in the rain, and put that on, even though it was about 80 degrees out. It took about an hour of rolling around under the trailer in the suit, and I was absolutely drenched in sweat when I was done, but the job is done and I can finally check it off my to-do list.

As an added bonus, I was able to coat the steel trailer frame (which was also un-coated and starting to rust), the frame of the truck, and the underside of my car. I am relatively happy with the results, but only time will tell if it will successfully protect the house. I'll provide an update in the future.

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