PVC, polycarbonate, and fiber-reinforced polymer (FRP) cladding systems offer durable, low-maintenance skins for sheds, greenhouses, and garden rooms. Modern formulations resist UV, impact, and thermal cycling far beyond early-generation plastics.
| Material | Profile | Light Transmission | Insulation (R-value) | Life | Best For |
|---|
| PVC (uPVC) Shiplap / V-Groove | Solid opaque | 0% | 0.5–1.0 (air gap) | 25–40 yr | Sheds, garden rooms, bin stores |
| Twin-Wall Polycarbonate | 6–16 mm | 40–80% | 1.4–2.5 | 15–20 yr | Greenhouses, cold frames, roof panels |
| Multi-Wall Polycarbonate (4–10 wall) | 16–35 mm | 35–60% | 2.5–4.0 | 15–20 yr | Insulated greenhouses, lean-tos |
| Corrugated FRP (Fiberglass) | 1.0–1.5 mm | 0–85% (grade) | 0.8 | 20–25 yr | Roofing, skylights, industrial |
| Solid Polycarbonate | 3–12 mm | 85–90% | 1.0–1.5 | 15–20 yr | Vertical glazing, doors, partitions |
Installation Principles
- Thermal expansion: 0.06–0.07 mm/m/°C — oversize fastener holes; use neoprene washers; don't over-tighten.
- Fasteners: Polycarbonate/PVC screws with sealing washers; 300–400 mm spacing.
- Purlin spacing: 400–600 mm (polycarbonate); 600 mm (PVC).
- Edge sealing: Aluminum U/F/H profiles; breather tape on top edge (prevents condensation ingress).
- Roof pitch: Minimum 5° (1:12) for drainage; 10°+ for polycarbonate.
Garden Structure Applications
Sheds & Garden Rooms
PVC cladding over OSB/plywood sheathing + breathable membrane. Insulate cavity (mineral wool, PIR) for conditioned space. Vapor control layer interior. PVC corner trims, window surrounds, fascia — complete weather envelope.
Greenhouses
Twin-wall polycarbonate on galvanized/aluminum frame. Automatic roof vents (wax cylinder or motorized). Shade cloth integration. Concrete knee wall + polycarbonate above = thermal mass + light.
Flat Roof Considerations
If cladding a flat roof (shed, lean-to):
- Minimum 1:40 fall (1.5°).
- EPDM/TPO membrane under cladding — cladding is not primary waterproofing.
- Internal drainage (sump + pump) or external gutter with adequate outlets.
- Walkable decks: FRP grating over membrane; cladding on parapets only.
Modified Bitumen Alternative
For flat roofs: SBS/APP modified bitumen (torch-down or self-adhered). Mineral surface (white/gray) reflects heat. 15–20 yr life. Requires professional installation — not DIY-friendly.
Cost & Value
- PVC cladding: $3–$6/sq ft material; $8–$14/sq ft installed.
- Twin-wall polycarbonate: $2.50–$4.50/sq ft; $7–$12 installed.
- Multi-wall: $4–$8/sq ft; $10–$18 installed.
- FRP corrugated: $1.50–$3/sq ft; $5–$10 installed.
Plastic cladding transforms garden structures from temporary to permanent assets. Match the material to the mission—opacity for storage, translucence for growing, insulation for comfort—and install with respect for thermal movement.
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