So in my last update I showed how I framed the floor (here) of my Tiny House and the next step was to insulate the floor cavity. When you frame the tiny house, most people frame it so that it hangs off the edge of the Tiny House on most of the sides. This creates a gap between the framing and the actual trailer. So we use expanding spray foam to close it up air tight. This foam creates a water and vapor barrier.
One major tip I can give you if you are using this stuff, wear latex/nitrile gloves that you can throw away. If this stuff gets on your skin it literally will not come off, even with paint thinner, goo gone, pumice soap, or any other trick you have in your book. You basically have to wait for your skin to wear off. trust me, I know!
First off, this is what I started with, the floor framed, beneath that you can see the white vapor barrier and that is covering the metal flashing. Then I sprayed the expanding foam into all the cracks to seal it up. From there I will be putting in the foam board, which I will show in my next update post.
Today I wanted to share with you all on how I framed the floor of my house. The framing was done with treated 2×4’s placed on 2 foot centers. The trick to framing is to have all your joists designed to both land on 24″ centers (so when you place sub flooring – 4 feet wide – you know exactly where to screw into the floor joists). The other thing you need to consider is the forces that the floor is going to be encountering, this effectively is your foundation, so it’s important for this to be really strong.
To add more strength I used corner braces that are used in hurricane prone area building, I also tied the floor joists to the deck of the trailer using high sheer strength screws. I screwed from below the trailer, through the trailer decking, into the joists. In certain key joints I chiseled out notches for the cross members to sit into, this wasn’t in the plans, but I thought the potential forces seemed to call for it. Here is a video and then a bunch of photos after that.
After removing the boards for the deck of my house, I then flashed the whole surface of the trailer with galvanized metal flashing. This will prevent moisture from getting into the insulation and floor framing and prevent mice or road debris from entering into the undercarriage. I made sure to overlap the seams and then used flashing adhesive to seal it all up. The sheets then were secured using staples and the vapor barrier was placed on top of that.
It’s worth noting my approach to moisture when it comes to my Tiny House. I have several layers of redundancy to prevent moisture from becoming and issue. First is the fact that the trailer is inherently off the ground, this means that there is a good air flow to dry out any moisture that does make its way under the house. I plan to have a gravel pad to facilitate better drainage under where the house is parked. From there I have the trailer decking which is pressure treated. I think it is very unlikely that much water will be able to get up underneath the trailer other than if I were to drive it down a road after/during a rain shower. From there I have a sealed layer of galvanized metal flashing. This will prevent any water from entering an because its galvanized, it is well adapt at handling it if it does. On top of that is a sheet of 6mil vapor barrier. On top of that is my floor framing and insulation. The floor framing is also treated and the foam is closed cell so it will not absorb any moisture. All in all I think moisture isn’t going to be a huge issue because of the air flow, but if it does get in, there are multiple layers to handle it.
First step was to cut a hole for the tiny house deck. The decking of the actual trailer is treated lumber, to cut the hole I used a sawzall to make the cuts.
Then I attached galvanized flashing to the deck, being sure to overlap the seams and seal them with flashing adhesive.
Then I added a 6mil vapor barrier.
Finally all my floor framing (covered in depth in another post) is all treated lumber.
Picking up my trailer was a very surreal moment for me. I think when I saw the trailer for the first time it finally hit me that I was committing to this project. It was a weird mix of emotions… excitement mixed with a touch of oh s%!$ I have to build a whole house! Even though I have been inside a Tumbleweed Fencl before, when I saw the trailer it seemed small. The interesting thing is now that I am building on it, it’s size seems to get bigger feeling. Even though it seemed small for a house, it was huge on the road! I had to go down this little side road to get home; at one point I looked in my side mirrors and my right tire was on the pavement’s edge and the left side was a foot into the other lane!
So now the nitty gritty details for those who want them.
The trailer is a 18′ utility trailer, its a 8,000 GWVR made by Kaufman trailers. Between the fenders it is 82.5 inches which is really important for to make sure your house is as wide as possible. Basically if you have you maximum trailer width, minus the tires, clearance from the axle/wheel wells you get about 82″. The decking is treated lumber and I opted to get a heavier duty trailer so I could just leave all the decking on instead of fooling with removing some of it like many houses do. This also means that I have a (almost) solid chunk of wood underneath my insulation which adds to the R value of my house. According to a web search this will add about R-3 to my already R-13, add the almost inch of flooring and then a 1/2 finished flooring we are looking a total of R 18.8 for the floor.
I took my trailer to a welder to add the tie downs and remove a bunch of parts. I had him cut off the rear light arms that you can see in the above photo, also the spare tire bracket and one part of the front “I” beam to make it flush with the front of the trailer. The tie downs are 4 bolts in the front, 6 threaded rods on the sides and two plates on the back. Check out the video below for more.
Here (below) is the front “I” beam that the top right arm of the “I” was cut off, you can see them cutting it off in the above photo.
In the above photo notice that I made the tie downs go in line with the cross members of the trailer. I will have to tweak the wall framing to accommodate, but it is much strong at this point.
Since the house extends about 6″ off the back of the trailer I needed more tie down spots and support. Above and below are photos of the rear tie down plates. I left them without holes because I wanted to be sure to place the hole exactly where I needed it to tie into the framing once it is built. Because of this I made the plates out of 6″ C channel and then had gussets welded onto them. These plates ended up being slightly too long, but I will just sheath this section of the house twice: the first layer will extend the surface beyond the plate’s edge and the second will hand down to attach the siding and hide the trailer from sight.
Today I have a quick video that I wanted to get up before I start working on my Tiny House today. It was pretty cold out this morning at 7am so I took advantage of needing to get a post up on the blog while it warms up a bit. Many people have asked how do you anchor a Tiny House to the trailer so that it doesn’t come off while moving down the road or get lifted off during a storm. This video will show my approach to this. I actually upped the number of attachment points from what the plans called for after talking with my weld who has spent 30 years in construction trailer frames for mobile homes, RV’s, and trailers. The important thing to note that I didn’t in the video is that the anchor points are aligned with the cross members of trailer which make it a lot stronger.