How have you finished the underside of your floor with post and beam?

[brian_nj]

I am still debating foundation options and a post below got me thinking on how to finish the underside of the floor with post and beam construction. I was thinking that after the insulation was done using 1/4" plywood to seal it in and then paint it with exterior deck paint. That should keep out the critters, lesson the wind infiltration and help with the rigidity of the floor. I cant see leaving it open to the elements, even if well ventilated it will retain some moisture. When I lived on the coast they used a weave like material it was about 1/4" thick and rigid like wood but even that after a couple years would crumble due to the moisture. Anyone have other suggestions or opinions on mine?

[MountainDon]

We used 3/8 CDX plywood to enclose the bottom.

We first pushed fiberglass insulation up against the sub floor in the cavities and held them in place with stiff spring wire stays. That would keep the insulation up in place with an air space between the insulation and 3/8 plywood.

Next we nailed 6 inch wide strips of 1/4 inch hardware cloth along the inside edge of the beam. The floor joists sit on top of the beams and the joists cantilever over the beam approx 12". So this mesh was placed at the inside edge of the beam, bent to a 90 degree angle and secured with nails fixing it to the beam and the joists.

Then 4x8 sheets of 3/8 ply were nailed in place, overlapping the mesh by an inch or so. The cantilevered portion was covered with ripped lengths of the 3/8 ply.

The sections under the area where the waste water pipe runs was affixed with screws, the rest air nailed.