Choosing a cladding material is often framed as a question of look and budget. In practice, the three families most often compared, natural stone, glass-fibre reinforced concrete (GFRC) and metal, behave differently in ways that reach the structure, the fixing system, the programme and the building's later life. A fair comparison looks at the whole wall: the panel, the support, the joints and what happens when something is damaged. This article offers a way to do that without leaning on a brand or a price.
Start with the system, not the surface
Most modern cladding works as a layered wall. The panel is the visible skin, but it hangs from a sub-frame, with a cavity and weather barrier behind. In a rain-screen arrangement, the panel sheds most rain and the cavity handles the rest. The guide to the cavity shows why that gap matters.
A comparison should therefore ask the same questions of each material. How is it held? How much load does it put on the wall? How does it move? How is it replaced? Photographs of the finished surface answer none of these. A sample, a drawing and a mock-up do.
Weight and what it asks of the structure
Weight is the first practical difference. Natural stone is dense and heavy, and a panel of useful size needs a strong support and anchors designed for its weight. GFRC is cast thin and is usually lighter than stone for the same area, though returns, ribs and large formats add weight. Metal panels are generally the lightest of the three and are easy to lift and handle.
Weight affects more than the wall. It affects the sub-frame, the anchors into the slab or wall, the lifting method on site and the number of workers needed per panel. A heavy material can be right where the structure and budget allow it, but it should be chosen with those consequences visible. Ask the facade consultant to compare the weight per square metre of the actual build-ups, including the frame.
Fixing and anchors
Each material is fixed in its own way. Stone is often held by concealed or exposed anchors that engage small slots or kerfs in the edge, or by back-fixed anchors that bond into the rear. GFRC panels commonly have cast-in or bonded inserts, with brackets that tie them back to the frame. Metal panels may be hung on rails, clipped, riveted or screwed, depending on the system.
The anchor is a safety-critical part. It must be designed for the panel weight, the wind load, the movement and the direction of loads, and it must be made of a material suited to the exposure. Ask for anchor drawings with materials, spacing and tolerance, and ask who is responsible for design and testing. The wind load guide explains what is being resisted.
Movement, joints and tolerance
All materials move with temperature and moisture, and the structure behind moves too. Metal panels expand and contract noticeably with temperature, which is why they usually have slotted fixings and open joints. Stone and GFRC move less with temperature but can respond to moisture and need joints sized for the full movement range, not just the visible width.
Tolerance differs as well. Metal is made in a factory to tight dimensions. GFRC is cast in moulds and is repeatable, though large panels need attention to flatness. Stone is cut from natural blocks, and variation in thickness and colour is part of the material. A joint that looks fine on a drawing may not accommodate the real variation, so design the joint for the material. See the movement joints guide for the principles.
Finish, colour and weathering
Stone offers texture and depth and ages in a way that people often value, but colour varies from block to block and between batches. GFRC can be coloured and textured to mimic stone or concrete and can be repeated across the building, though the surface may carry some variation depending on mix and process. Metal can be painted, anodised or finished with a high-performance coating, and gives the sharpest edges.
How each material weathers is part of the choice. Rain streaks, staining at sills, dirt on textured surfaces and the effect of salt air differ from one material to another. The finishes guide compares common metal coatings. For stone and GFRC, ask the supplier for weathered examples of the same material, and for a cleaning method that will not damage the surface.
Shape and design freedom
Metal is the most flexible for complex forms, folds, curves and perforation. GFRC allows deep returns, curves and sculpted shapes through moulds, with the cost of the mould spread across repeated panels. Stone is best at simple planes, with shaped pieces costing more and taking longer. For ideas on the metal side see the terracotta, HPL or ACP guide and the ACP and solid aluminium guide.
If the design needs many unique shapes, the economics change. A mould that makes one hundred identical panels is efficient. A mould that makes five each is not. Ask the manufacturer to show how many unique panel types the design contains, and whether a modest rationalisation would give the same impression.
Fire, safety and the cavity
Materials respond to fire differently, and the cavity behind a cladding wall needs to be designed with fire barriers and compartmentation in mind. National rules govern which materials may be used at which heights and for which building types. Do not rely on a general statement. Ask the consultant to confirm the whole build-up against the applicable rules, including insulation, fixings and cavity barriers.
Safety in handling is also part of the comparison. Heavy panels carry risk during installation and any later replacement, and the access method should be considered at design stage. The installation sequence guide describes the order of work.
Each material has its own supply pattern. Stone depends on a quarry, a block selection and a cutting and finishing sequence, and the earliest stages happen well before panels reach site. GFRC depends on mould making, curing and quality checks. Metal depends on sheet or extrusion supply, forming and finishing. Ask each supplier to set out the steps from order to delivery, and where the programme risk sits.
Samples are the most useful tool here. Ask for full-size panels, with the real edge, joint and finish, and view them outdoors in the light they will have on the building. For stone, agree how many blocks are reviewed and who approves the range. For GFRC and metal, agree the colour tolerance between batches. Write those decisions into the specification so the approved sample is the standard.
Supply, repair and replacement
Facade materials last for decades, so repair matters. Can a single panel be removed without disturbing its neighbours? Can a cracked stone be replaced in a matching colour many years later? Can a dented metal panel be swapped? Ask how each panel is held, in what order they come off and what spare stock is advised.
Cleaning is part of the same question. Some surfaces can be washed from a cradle with water and a soft brush, while others need specialist treatment. Record the cleaning regime in the handover manual, and read the facade maintenance checklist for what to look at on inspection.
A simple way to compare
- Weight per area of the full build-up, and what it asks of the structure.
- Fixing and anchor design, with materials and who is responsible.
- Movement, joint width and tolerance for the real material.
- Finish, colour range and how it weathers on a site like yours.
- Shape: how many unique panels the design needs.
- Fire and code route for the whole wall.
- Repair, replacement and cleaning over the building's life.
Put those answers beside each other for each option and the real differences show up. Then ask for a mock-up of the shortlisted options, because the look, the joint and the weathering are best judged in a full-size bay. See also the value engineering guide for how to protect performance if costs are reviewed.
General guidance for orientation, not a specification. Applicable standards, values and details are confirmed per project with the facade consultant.
