Heavy-duty work trucks and older vintage vehicles develop rust. Often, rust will leave gaps and small- to medium-sized holes in the floor of the passenger cabin. Expanding foam and cardboard can be used to repair minor perforations in a rusted truck floor. Fixing the rusted floor will help protect the cabin and the occupants.
Pull back the carpet (if present) to expose the metal floor. Sand rusted spots and vacuum loose rust particles.
Cut pieces of cardboard several inches larger than the diameter of each floor hole. Lightly coat these pieces with silicone spray so you can peel them away when the foam is cured. The cardboard will help contain the expanding foam to the area that needs to be filled.
Tape the sprayed cardboard securely below the floor pan and around the hole so that it will "mold" the foam along the bottom contours of the perforation as it expands.
Put on the rubber gloves. Place the extension tip on the nozzle of the expanding foam canister. Insert the tip into the holes in between the upper and lower sections of the floor pan. Press the nozzle in short bursts, allowing the foam to expand. Continue spraying the foam until it fills the space created by the cardboard mold pieces.
Let the expanding foam cure for 24 hours. Peel away the cardboard used to form the foam.
Cut off any excess foam protruding up into the cabin as needed with the drywall saw. Lightly sand the surface of the dried foam so it is flush with the floor pan.
