How do sandwich panels reduce the tare weight of a motorhome?

compoform · 21 Aug 2026

Sandwich panels reduce the tare weight of a motorhome by replacing heavy wood and metal structural elements with a lightweight composite construction: a low-density core material bonded between two thin, high-strength skins. The result is a panel that delivers comparable or superior structural performance at a fraction of the mass. The sections below unpack how this works in practice, from materials to structural performance to panel selection.

This article covers the broader sandwich panel market. Compoform’s range is limited to PP honeycomb and PET foam cores for commercial vehicles and motorhome applications.

What materials are traditionally used in motorhome construction?

Traditional motorhome construction relies on timber framing, plywood panels, and sheet metal for walls, floors, and roofs. These materials are widely available and easy to work with, but they carry a significant weight penalty. A plywood wall panel, for example, can weigh two to three times more than a composite sandwich panel of equivalent thickness and stiffness.

The typical material stack in a conventionally built motorhome includes:

Structural framing: softwood or hardwood timber, sometimes aluminium extrusions
Wall and ceiling panels: plywood or MDF, often finished with a decorative laminate
Floor substrate: plywood, sometimes reinforced with a steel or aluminium subframe
Exterior cladding: aluminium sheet or glass-fibre reinforced panels over the timber frame
Insulation: mineral wool or rigid foam boards inserted between frame members

Each of these layers adds mass. Timber absorbs moisture over time, which increases weight further and accelerates deterioration. Steel and aluminium subframes add structural dead weight that contributes nothing to payload capacity. The cumulative effect is a tare weight that leaves less room for passengers, equipment, and supplies within the legal gross vehicle weight limit.

How does a sandwich panel’s structure reduce overall weight?

A sandwich panel reduces weight by separating two thin, stiff skins with a lightweight core, achieving high bending stiffness without the mass of a solid material. The core keeps the skins apart, which dramatically increases the panel’s resistance to bending loads. This means you can achieve the same structural performance with far less material and far less weight.

The structural logic mirrors an I-beam: the flanges (skins) carry tensile and compressive forces, while the web (core) resists shear and keeps the flanges at the correct distance. In a sandwich panel, the skins are typically glass-fibre reinforced thermoplastic laminates, and the core is either a polypropylene honeycomb or a PET foam. Both core types are predominantly air by volume, which is why the overall panel density is so much lower than solid timber or metal.

In practical terms, this construction replaces multiple separate layers, framing, insulation, interior lining, exterior cladding, with a single integrated panel. That consolidation removes not just material weight but also the fasteners, adhesives, and labour associated with assembling those layers. A motorhome wall built from sandwich panels requires fewer components, fewer assembly steps, and produces a lighter finished structure.

How much weight can sandwich panels save in a motorhome build?

The weight saving depends on which materials are being replaced and the specific panel configuration chosen, but switching from timber-framed plywood construction to thermoplastic sandwich panels typically reduces wall and floor panel weight by a meaningful margin. Sandwich panels consolidate structure, insulation, and cladding into one element, removing the cumulative mass of multiple separate layers.

A few reference points illustrate the scale of the saving:

A plywood wall panel at 12 mm thickness weighs roughly 8 to 9 kg per square metre. A thermoplastic sandwich wall panel of similar or greater thickness can weigh considerably less, depending on core density and skin specification.
Eliminating a steel or aluminium subframe from the floor, which is possible when a self-supporting sandwich floor panel is used, removes a structurally significant mass from the build.
Across a full motorhome shell (walls, floor, roof, and internal partitions), the aggregate saving across all panels can translate into a meaningfully lower tare weight, freeing capacity for payload within the legal gross vehicle weight limit.

It is important to note that actual savings vary by specification. Core density, skin thickness, and panel dimensions all affect the final weight. The right approach is to compare the total system weight, panel plus any required substructure, rather than the panel alone.

Does lower tare weight affect motorhome performance and payload?

Yes. A lower tare weight directly increases the usable payload within the vehicle’s legal gross vehicle weight limit, and it also improves fuel efficiency and handling. Every kilogram removed from the structure is a kilogram that can be reallocated to passengers, water, equipment, or supplies without exceeding the permitted total weight.

For motorhome owners and manufacturers, this matters in two distinct ways:

Payload capacity: Many motorhomes operate close to their gross vehicle weight limit when fully loaded. A lighter shell gives occupants more headroom to carry what they actually need. For manufacturers, a lower tare weight is a competitive specification that directly influences purchasing decisions.

Fuel and energy efficiency: A lighter vehicle requires less energy to move. For motorhomes powered by conventional engines, this translates to lower fuel consumption over a journey. For electric motorhome platforms, which are beginning to enter the market in 2026, the argument is even more direct: lighter body structures extend battery range. Every kilogram of structural dead weight reduces range per charge. This makes weight reduction a range argument, not just a payload argument, and it is an increasingly standard question from buyers evaluating electric leisure vehicle platform applications.

Are sandwich panels structurally strong enough to replace wood and metal?

Yes. Properly specified sandwich panels are structurally capable of replacing timber framing, plywood, and metal sheet in motorhome construction. The key is matching the panel configuration, core type, core density, skin architecture, and thickness, to the specific load demands of each application area.

Glass-fibre reinforced thermoplastic skins provide high tensile stiffness and impact resistance. The cross-ply skin architecture, where fibres are oriented at 0° and 90° in alternating layers, equalises mechanical properties in both directions, making the panel perform consistently regardless of installation orientation. This is relevant for wall panels that may experience wind loads, point loads from fixtures, or racking forces during travel.

For floor applications, where compressive and bending loads are more demanding, PP honeycomb cores at higher densities deliver substantially greater load-bearing performance than foam-core wall panels of similar thickness. A well-specified sandwich floor panel can be self-supporting, eliminating the need for a separate aluminium subframe entirely. This removes a production step, reduces cost, and further lowers the overall build weight.

Sandwich panels also outperform plywood in durability. In demanding transport applications, thermoplastic composite panels last considerably longer than plywood, which is prone to delamination, moisture ingress, and rot. Over a vehicle’s service life, this durability advantage eliminates multiple replacement cycles and the associated downtime and labour costs.

What types of sandwich panels are used in motorhome manufacturing?

Motorhome manufacturers use different sandwich panel configurations for different areas of the vehicle, because each zone has distinct structural and environmental requirements. The main panel types are differentiated by core material, core density, and skin architecture.

Wall and ceiling panels

Wall and ceiling panels prioritise low weight and a finished surface appearance. These typically use a lower-density foam core, oriented PP foam or PET foam, bonded to glass-fibre reinforced thermoplastic skins. A white PET-film surface finish provides a clean, decorative interior face without requiring additional lining. The cross-ply skin architecture distributes load evenly in both directions, which is useful for panels that carry fixture loads from cupboards, windows, and fittings.

Floor panels

Floor panels carry higher compressive and bending loads and must resist point loads from furniture legs, occupant movement, and heavy equipment. PP honeycomb cores at higher densities are common in this application because they deliver greater bending and compressive performance than foam cores of equivalent thickness. An anti-skid surface finish on the top skin is standard for safety. A well-specified floor panel eliminates the need for a separate subframe, simplifying the assembly process.

Roof panels

Roof panels need to balance low weight with adequate stiffness to resist wind uplift and the occasional point load from roof-mounted equipment. Foam-core panels are common here, with skin thickness and core density selected to meet the specific span and load requirements of the roof geometry.

How Compoform Helps with Motorhome Sandwich Panel Specification

We manufacture thermoplastic sandwich panels specifically for applications where weight, durability, and dimensional precision matter. For motorhome and leisure vehicle manufacturers, we offer panels across the full range of configurations needed for a complete build: wall panels, floor panels, and custom formats for roofs and internal partitions.

What we bring to a motorhome project:

Custom dimensions: Panels are produced in sizes up to 13,500 mm × 2,950 mm, which means we can supply full-length wall or floor panels without joints, reducing assembly complexity and potential weak points.
Core and skin selection: We work with you to select the right core type and density for each panel zone. A wall panel and a floor panel in the same vehicle will have different specifications, and we configure each accordingly.
Self-supporting floor panels: A correctly specified PP honeycomb floor panel is self-supporting, removing the need for an aluminium subframe. This reduces build cost and lowers tare weight in a single step.
Surface finishes: White PET-film surfaces for interior walls provide a finished decorative face with over 22,000 hours of UV resistance, tested to ISO 4892. Anti-skid finishes are available for floor panels.
European production: All panels are manufactured at our facilities in the Netherlands, which means consistent quality, reliable lead times, and no supply chain exposure to long-distance logistics.

We do not ship panels to a specification and leave you to work out the rest. Before production, we review your design, assess the load requirements for each panel position, and flag any configuration choices that could create problems during assembly or in service. If your design can be optimised, we will tell you before the panels are made.

If you are specifying sandwich panels for a motorhome or leisure vehicle build and want to work through the configuration with an engineering team that knows the application, get in touch with us to start the conversation.