Water is a major concern when it comes to building a tiny house on wheels. In fact, it’s right up there with weight. We need to keep the house light, and water tight. From the start, we wanted to give serious thought to just how we were going to accomplish a leak-free house. A tiny house on wheels proves to be a bit more of a challenge in this regard, after all it is a moving structure, and has a weird foundation that includes wheel wells.
We did our research: countless videos were watched, articles read, contractors consulted. We saw examples of successful flashing….and the not so successful. We witnessed the mistakes of others, and took note. Then we sat down and discussed it between ourselves, trying to come up with the best way to flash the house. Let me just say, we tend to overkill on these things.
I swear, when I first heard the term capillary action, I heard caterpillar action….and I totally imagined a caterpillar dancing. Your imagining it too now aren’t you? Your welcome. Capillary action is when dripping water get’s to the end of something and sort of wicks back up behind it, in this case our siding. So we plan on having a rain screen between the house wrap and the siding, however we were also concerned about any water dripping to the base where the sheathing meets the trailer and rotting out our floor. So this is what we came up with….
We took this dangerously sharp bit of metal called Z Flashing:
….and installed it on the bottom of the house like so:
We installed the Z flashing all along the very bottom of the sheathing. Usually Z flashing comes out from under the sheathing, as shown in this photo:
But we wanted to keep water from dripping down the bottom of the plywood – gotta keep those plywood ends from rotting out. We attached it with nails about every 12 to 16 inches, then we used Tyvek tape to fasten the house wrap to the upturned leg of the flashing. So if we ever have a leak, any water that runs down the Tyvek will hit that flashing, and drip out and away from the base of the house and trailer frame. And with spacing the nails that far apart, we were able to leave a slight gap between the flashing and the sheathing, so if water ever happens to get behind the Tyvek (which it shouldn’t ever happen, but you never know), it wont get trapped.
This Is Where
We I Went A Bit Overboard.
The wheel wells are the most tricky. Hence, this is the bit where my anal retentiveness reared it’s ugly head. So you may recall in this post here, we showed you how we went about sealing the gap between the sheathing and the metal wells. Which has worked out great. Many other tiny house builders have done the same, and in fact that is all they used. But all it took was the one little thought of: ‘What if the sealant should crack, break or fail? Then what?’. That tiny seed of doubt resulted in some heavy duty flex-wrap:
So now we have a buff should-never-crack sealant, covered with a heavy duty flexible flashing wrap, capped with Z flashing, and then covered with Tyvek and Tyvek tape:
We also left a slight gap between the bottom of the Z flashing and the wells, in case any water should flow under it, it can then escape or dry out.
It may be overkill, but I will rest easy knowing that any standing water on the metal wells will not be able to wick back up onto the sheathing. Wet pacific northwest – bring it on!