The area of the wheel wells for tiny houses on trailers is often the peskiest place prone for leaks. Since they also protrude into a tiny house they require some work and fore thought to insulate and cover.
At Tiny Green Cabins, when we are building the tiny house, we like to make sure we follow our steps to guarantee we have minimized the possibility of a leak.
We use a building gasket on our plates and around the wheel well where the plates meet the well. We staple the gasket to the bottom of the wood plate and attach the plate to the wheel well by drilling from the underside of the wheel well to the wood/metal bottom plate. Then we use a stainless steel screw to secure the wheel well to the plate. As the plate compresses against the wheel well, it forms a tight seal on the inner and outer side of the plate.
BUILDING GASKETS: Building gaskets are designed to seal under heavy loads, such as under sill plates, wall plates, roof panels, wall panels, and rim joists. Since they are effective moisture barriers, they eliminate the need for damp proofing between wood and masonry or concrete foundations. They come in 3 sizes: BG65 for 2 x 6’s, BG63 for 2 x 4’s, and BG61 for edges of rim joists, joints in exterior foam sheathing, or connections between stress-skin panels and posts or purlins.
Then as we apply other exterior layers in the wheel well area, we back caulk such as the wall sheathing. Before we apply the sheathing, we run a heavy bead of Vulkum caulk around the wheel well to the plates and then install the wall sheathing. The wall sheathing presses into the caulk adding another layer of sealant to prevent water infiltration. The last bead of caulk that is applied is at the siding face; we apply a continuous clean bead of caulk that is tooled to a nice finishing look.
On the inside of the wheel wells, we building what we call a wheel well cover that has a 3” air space between the wheel well and cover. We then fill that space with a large gap expanding foam insulation such as from Great Stuff. Once that foam has cured, we remove any excess of foam and apply the top of the wheel well cover. From there it is personal preference on how best to camouflage the wheel well, such as with built in book cases, a couch, or desk.