Insulating Your Tiny House Wheel Well Undercarriage

Before too much weight is on your trailer, you may want to consider insulating the undercarriage of your wheel wells.  If you desire a really tight house, and very likely will have walls built on top of your wheel wells, you may want to consider this additional (but in our opinion necessary) step.

Some of the items you may need (which may or may not apply to you based on your trailer design) are:

  1. Foam board insulation (1″ & 1/2″) 2) Rubberized undercarriage paint 3) Glue (in our case subfloor caulking) 4) Wood to metal screws w/ washers 5) Oxboard.  What is Oxboard you say? It’s really awesome structural insulated sheathing; we will discuss Oxboard more up the road in an extended insulation post. We used 1/2″ which provides R3 insulation in the wheel well in addition to the foam board.

In our trailer design, the wheel wells were customized (through Wishbone Tiny Homes to be watertight, structural wheel wells. In between some of the plates were areas we placed 1″ foam board, which formed the first layer for the top and sides of the wheel wells.  While it may be obvious, you’ll need to remove the wheels to do these steps, so do it all before there is a heavy load on your trailer!

foam board added to wheel well undercarriage
Subfloor glue to hold the next 1/2″ foam board in place.
undercarriage wheel well foam board
1″ foam board in undercarriage of structural wheel well.

 

 

 

 

 

Our second layer was 1/2″ foam board cut to fit. You want to place these like you would drywall so they help anchor each other in place. The third layer is the 1/2″ Oxboard (structural sheathing). So right off the bat, we have between 6-11 R value to insulate the bottom of our walls, in addition to whatever insulation you’ll have above & in your walls. Self-tapping wood to metal screws (2 3/4″) with washers were used to anchor it all into place:

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This is what it looked like before going to our next step. Keep in mind you’ll want some wiggle room behind your wheel drums, and that while you may have so much cavity room above your wheels, that will be subject to change. Even with the 1.5″ of insulation above the wheels, we allowed enough room for the wheels to raise from weight and when traveling:

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Next you’ll want to seal your insulation somehow.  We just used Gorilla duct tape; anything that acts like flashing tape should do.  This is because rubberized paint will be added on top. Tape was added around the wheel well, all seams, and underneath:

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Last step (other than placing the wheels back on!) is the undercoating paint. We gave everything two coats (just to be safe):

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If your wheel wells look exactly like how they started (despite all the work you did), then you did your job!

insulated wheel wells
Insulated wheel wells- done!
insulated wheel wells
What it looks like once your wheel well undercarriages are insulated… exactly the same as you started!

Do you have a similar trailer design and insulated your wheel well undercarriage some other way? Let us know!

2 thoughts on “Insulating Your Tiny House Wheel Well Undercarriage

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