Multiwall sheets – materials, applications, differences and installation
Which multiwall sheets are the right ones? Materials, differences, prices, installation – all in one comprehensive guide with tips and practical tables.
Multiwall sheets – also known as twin-wall sheets – are multi-wall plastic sheets whose internal structure consists of parallel webs. This structure creates insulating hollow chambers that save weight while providing stability.
Multiwall sheets are usually made of polycarbonate, acrylic glass (PMMA) or PVC. They are UV-resistant, light-transmitting and weather-resistant – properties that make them particularly suitable for roofing, greenhouses and carports.
Differences from similar products:
- Solid sheets: No hollow chambers, heavier, more expensive
- Corrugated sheets: Single-wall, no insulation, more for simple roofs
- Light sheets: Collective term for transparent roofing materials, not always insulating
Materials compared – what is suitable when?
| Material | Advantages | Disadvantages | Recommended for |
|---|---|---|---|
| Polycarbonate | Extremely impact-resistant, UV-resistant, temperature-stable | Scratch-sensitive, slightly more expensive | Carports, industry, hail regions |
| Acrylic glass (PMMA) | Highest light transmission, UV-resistant, dimensionally stable | Less break-resistant | Conservatories, terraces with design requirements |
| PVC | Inexpensive, easy to process | Short service life, yellows faster | Temporary solutions, simple roofs |
What variants are there?
Multiwall sheets differ not only in material but also in construction:
| Type | Construction | Advantages |
|---|---|---|
| Single-wall multiwall sheet | Two layers, one chamber | Very light, inexpensive |
| Twin-wall sheet | Three layers, two chambers | Good thermal insulation, stable |
| Triple-wall / X-structure | Several hollow chambers, with cross or X bracing | Best insulation, maximum flexural rigidity |
| IQ sheets | Multi-layer high-tech sheets with air chambers | Energy-saving, very long-lasting |
Additional functions of modern multiwall sheets provide extra benefits in application: "NoDrip" or "AntiDrop" coatings prevent the formation of condensation and ensure that moisture runs off as an even film of water instead of condensing into drops. "HeatStop" or "CoolLight" technologies reflect a large proportion of solar radiation and thus reduce heating beneath the sheet – ideal for covered seating areas or conservatories.
The "UV+" function denotes UV protection on both sides, which is particularly important for self-supporting applications or open structures, as both sides of the sheet can be exposed to solar radiation.
What do multiwall sheets cost?
| Material | Price range (€/m²) | Example 6 mm sheet |
|---|---|---|
| Polycarbonate | 18–35 € | approx. 25 € |
| Acrylic glass | 25–45 € | approx. 32 € |
| PVC | 10–18 € | approx. 13 € |
Price factors:
- Thickness: More chambers = higher price
- UV coating: Single or double-sided
- Colour: Opal/bronze more expensive than clear
- Format: Cut to size or standard size
Application: Which multiwall sheet for which project?
| Application | Suitable material | Rec. thickness | Notes |
|---|---|---|---|
| Terrace roof | Polycarbonate, acrylic glass | 10–16 mm | UV-protected, light-transmitting |
| Carport | Polycarbonate | 8–10 mm | Impact- & hail-resistant |
| Greenhouse | Polycarbonate, PVC | 4–6 mm | Insulation value important, inexpensive solution possible |
| Conservatory | Acrylic glass | 16 mm+ | Highest light quality & insulation |
| Industrial hall | Polycarbonate (X-structure) | 10–25 mm | Span & insulation decisive |
Avoiding typical mistakes
- Wrong sheet thickness: too thin under high load
- No UV layer taken into account: leads to yellowing
- Doing without closing profiles: dirt and algae penetrate
- Silicone used instead of suitable sealants
Installing multiwall sheets – step by step
Preparation:
- Load-bearing substructure made of wood, steel or aluminium
- Slope: at least 5° (9 cm per linear metre)
- UV-coated side facing outwards
Cut to size:
- With a circular saw (fine saw blade)
- Only remove the protective film completely after installation
- Deburr edges
Fastening:
- Spacers + stainless steel screws with rubber seal
- Profile connectors made of aluminium or plastic
- Antidust tape (open chamber ends) + closing profile
Construction (illustrated):
A typical connection looks as follows: An H-profile or click system is placed between two sheets. Before insertion, a sealing tape is stuck to the underside of the profile. The sheet ends finish with approx. 5 mm clearance from the groove to allow for expansion. The ends are sealed with antidust tape and protected by a closing profile.
Installation notes:
- Do not create mechanical stress (thermal linear expansion!)
- Never use silicone – only system-compatible sealants
- Fix sheets only at points – do not glue over the entire surface
Accessories – what you really need
| Accessory | Function |
|---|---|
| Connecting profiles | connect sheets without stress |
| Closing profiles | protect edges, prevent dirt ingress |
| Antidust tape | prevents dirt & algae in the chambers |
| Sealing tape | water- and windtight sealing |
| Screws with spacers | stress-free fastening |
Buying advice: How to make the right choice
Answer the following questions before purchase:
- Where will the sheet be used? (e.g. terrace, greenhouse, industry)
- What light transmission is desired?
- Is there a risk of hail or wind load?
- Does it need to be insulated (conservatory, plants)?
- How long is the desired service life?
Tip: Always buy multiwall sheets as a complete system (incl. profiles, sealing tape, accessories) to prevent later leaks and complaints.
Direct to the right solution:
- Buy twin-wall sheets online
- General overview of multiwall sheets
Selecting multiwall sheets specifically & installing them safely
Multiwall sheets offer an ideal combination of light, protection and insulation. The decisive factor is choosing the right material, the right thickness and a professional installation system. With polycarbonate or acrylic glass you are on the safe side in most cases – provided you prioritise quality over cheap imports. Take advantage of the option to order multiwall sheets cut to size – suitable for your project.
FAQ – Frequently asked questions about multiwall sheets
Which multiwall sheets are better – acrylic or polycarbonate? Polycarbonate is more impact-resistant and break-resistant, acrylic glass offers clearer light and is more UV-stable. For terraces: either is possible. For carports: polycarbonate.
How long do multiwall sheets last? 15–20 years with UV coating and professional installation. Cheap PVC sheets often only 5–8 years.
Are multiwall sheets walkable? No. Only with a substructure designed structurally for this – never walk on them freely!
What should be observed when cleaning? No solvents, no rough sponges. Use only water, soap and soft cloths.
Can you install multiwall sheets yourself? Yes – with planning, instructions and suitable tools. Important: allow for expansion clearance, use accessory systems.
Which colour is ideal? Clear: maximum light transmission. Opal: glare-free, for living areas. Bronze: slightly shading, elegant appearance.
What about fire protection? Polycarbonate sheets usually meet fire class B2 or E (normally flammable). For public areas or special requirements, DIN-compliant products should be chosen.
Are multiwall sheets recyclable? Yes – many sheets are made of single-grade plastics and can be recycled. Disposal via the recycling centre or building materials trade is possible.
How high is the light transmission? Clear: up to 84 %, opal: approx. 76 %, bronze: approx. 60 %. Acrylic glass usually has higher light transmission than polycarbonate.
What is the U-value of multiwall sheets? Depending on construction, between 3.5 W/m²K (single) and 1.4 W/m²K (multi-wall). The thicker and more complex the structure, the better the thermal insulation.
