You will need to remove the interior of the RV in order to gain access to the area requiring repair. Remove all cabinets, appliances, walls, ceiling panels, and flooring. Always disconnect the LP gas at the tank prior to working on the RV. Run all power tools off of shore power (power at a campsite or home), do not use the RV's electrical supply. Soft wood like aspen, exterior grade plywood, and OSB are suitable woods for repairing RVs. Wall and ceiling repairs will require the removal of aluminum panels. This is not possible with fiberglass siding and Airstream RVs.
Start by making the repairs to the flooring first and then work your way up to the ceiling. Cut out the old subfloor with a hammer and chisel. If there is damage to the floor joists, remove as much as the subfloor as needed to get to the joists. Save any subfloor that is in good condition. To replace a floor joist, cut out the damaged section. Remove the ends completely where they attach to the frame. Slide in a replacement joist and secure it to the frame. The procedure is similar with wall supports. The siding of the RV must be removed to repair the wall supports. After the siding is removed, cut out the damaged supports and replace them. Ceilings can be repaired from the inside of the RV, but if you can peel back the roof and work from the outside it is easier. Cut out all damaged wood and replace with new wood.
If the rafters of the RV require repair or replacing, careful measuring is required in order to get the roof to fit back on the RV correctly. When possible, measure the angles of any rafters that require replacing or use the old rafter as a template for the new one. Install the new rafter by attaching it to the frame piece at the top of the wall.
