How to Repair RV Hardwall

Written by john cagney nash
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How to Repair RV Hardwall
Fibreglass hardwall is a versatile RV siding. (rv, image by Greg Pickens from

Recreational vehicles, or RVs, are constructed with outer skins typically made of either aluminium or fibreglass hardwall, also known as hard-siding. While both are durable and waterproof, the hardwall is simple to clean, experiences less flexing when under way, is convenient to maintain and is easier to polish to a shine. Heat transfer insulation efficiency is dramatically increased and noise transfer is minimised, a consideration when camping near roads or beside other RVers who are using generators. Hardwall is prone to delamination after a leak, and repairs can be complex and time consuming.

Skill level:

Things you need

  • Plastic-handled screwdriver
  • Brush and dustpan
  • Soap and water
  • Clean rag
  • Medium grit sandpaper
  • Dewaxing solvent
  • 2-inch blue painters' tape
  • Marker pen
  • Dust sheets
  • Wet-dry vacuum and duct tape
  • Jigsaw with scrolling blade OR
  • Hand-held circular saw with plywood blade OR
  • Spiral saw with heavy duty tile bit OR
  • Angle grinder with metal cut-off blade
  • Protective clothing

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  1. 1

    Tap the butt of a plastic-handled screwdriver on the hardwall to determine the boundaries of the repair. Damaged hardwall makes a dull and muted sound, while undamaged hardwall makes a sharp, clean sound.

  2. 2

    Mark where your cut will be made. It should be two inches beyond the damage to keep the removal and repair as neat as possible, and square in shape to facilitate an easier repair. Remove loose material by sweeping, then wash the area with soap and water. Use a clean rag to dry off, then use medium grit sandpaper to buff the cutting line, which ensures the repair will bond well to the cut rim.

  3. 3

    Use a new rag to rub on acetone or other dewaxing solvent. Ensure all oil and sanding dust is removed from the cutting line, then apply painter's blue masking tape where the cut is to be made. Two-inch tape minimises hardwall splintering along the cut line. Redraw the cut line on the tape and cut through the tape to ensure a clean cut. Cover the area around your project with dust sheets, and use duct tape to fix a vacuum nozzle beneath where the cut is to be made. Run the vacuum all the while you are cutting, and move the nozzle as the cut progresses.

  4. 4

    Make the cut from the inside out, if access is available, because the seam will experience less fracturing. Cut the hardwall with one of the following tools: a metal cut-off blade in an angle grinder, a heavy-duty tile bit in a spiral saw, a scrolling blade in a jigsaw or a plywood blade in a hand-held circular saw. Use carbide-tipped, fine-toothed blades.

  5. 5

    Set your cutting tool at a slow speed and move it gently and smoothly along your marked line. Moving too fast will overheat the cutting blade, which will dull or snap prematurely. If the cutting blade discolours it is about to break, and you must slow your pace.

  6. 6

    Taper the external rims of your cut using an angle grinder. This creates a larger bonding surface for the repair.

  7. 7

    Use a proprietary fibreglass repair kit to patch the hole, carefully following all the manufacturer's instructions and in strict sequence. Wear protective clothing that includes a long-sleeved shirt and gloves, because rogue fibreglass filaments are extreme irritants. Observe all the safety warnings in the repair kit manufacturer's literature concerning the breathing of fibreglass resin fumes.

Tips and warnings

  • Some RVers see hardwall leak delamination as an advantage, because aluminium siding offers no clue of water leakage until damage is advanced.
  • Aluminium siding is more prone to impact damage from accidental contact, so if you anticipate using your RV in areas prone to extremes of weather such as hailstones, hardwall is a better option.
  • Hardwall is more difficult to remove than aluminium siding if sub-skin repairs must be made to bent frame rails or support hoops.
  • Hardwall's increased rigidity comes at the cost of additional weight, typically approaching an extra thousand pounds in a 30-foot RV.

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