Subfloor Road Guard

Whats in this post:
Installing a shield for deterring critters and road debris from invading our residence from beneath.  We chose 20 gauge galvanized steel sheets

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Because we desire to live in wild places where critters who eat wood abound, and to protect our home from road hazards while towing we chose to install a heavy Subfloor Sheathe.
The “Sheathe” is the outer surface layer of a structure, regardless of orientation. So what we are seeing now is the lower sheathe of the floor, the bottom of the metal is exposed to road, and sits on top of the Pressure treated, double coated foundation boards. We chose galvanized sheet metal for its resistance to rust, and we chose 20 gauge to help insure that if we run over road debris we don’t acquire a new “volunteer” vent in the floor at the same time. Here we see my cutting tool, a simple angle grinder (wear gloves, eye and ear protection!!!) And next to that is an underside view, showing one of two heavy cross supports on our Tiny House trailer by Ronco Trailers

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Simply put: critters don’t eat metal. They may be able to gnaw through wires, but not even a honey badger could dig a hole through 20 gauge! So Termites, beetles, rats, mice, whatever… No Access through My Floor!!! Later on we trim the sides of the floor with Aluminum roll flashing. Less likely, though still something to be considered is Road Debris.  I am fine with dents, even a small gouge, which I can repair easily. But I really want to avoid having a branch or metal fragment shoot up through my floor… As I said, unlikely chance, but I am building a structure I intend to last for 50 years or more. So, We chose heavy metal  for our subfloor sheathe.

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On top of that we put a layer of rated OSB, sealed with silicone at the edges and joints. we left the recommended gap, though the measurement escapes me.  We used masonry twine to mark the foundation joists underneath. We used 1 3/4″ deck screws to secure both to the foundation, approximately 220 of them total, plenty of horizontal sheering resistance.

In retrospect OSB might not have been the best choice. It was cheap and light, but doesn’t do well with moisture. I really wanted some wood between my metal lower sheathe and the insulation. I also wanted to add a bit of tensile strength to the metal. Additionally, I wanted some wood to glue the subfloor joist beams to to preclude the possibility of sanity destroying floor squeaking. I probably should have used thin plywood instead. We had stretched our funds to the limit at the time so this is it.  I am doing my best to keep water out!

Key Points:
We galvanized metal to resist rust and moisture.
We overlapped the metal and sealed with silicone at the overlaps and edges where the OSB sat on top.
We used sturdy deck screws to secure the sheets down, exterior rated to resist moisture and rust.
We used masonry twine to mark where the joists were underneath to accurately place our screws.
We pre-drilled every hole to penetrate the sheet underneath and avoid inherit issues with driving a screw into PT board.
A metal sheathe on the bottom adds weight, but provides nearly unparalleled protection.

We obtained our Galvanized sheet metal from a local supplier. We used 4′ x  10′ sheets and I used the left over pieces to fabricate internal wheel-wells later on.
Competitive Metals –
Tel:  619.442.4130 – Fax: 619.442.4167 -135 Cypress Lane – El Cajon, CA 92020


One thought on “Subfloor Road Guard

  1. Pingback: Floor Top Sheathing | The Roots of our Tiny Life

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