Key takeaways
- Establish the radius first — it eliminates most candidates before appearance is considered.
- Wet-applied and small-module finishes follow curves; rigid sheets have a stated minimum radius.
- The substrate has to be curved accurately; the finish cannot correct a faceted backing.
- Convex and concave curves have different minimum radii for the same product.
Continue exploring all interior wall finishes and surfaces guides.
Radius first
Before discussing appearance, establish two numbers: the radius, and whether it is convex or concave. Together they eliminate most of the shortlist.
Every rigid sheet product has a minimum bending radius, published by the manufacturer, and it is frequently different for convex and concave bends of the same material. Below that radius the sheet does not bend — it cracks, delaminates or takes a permanent set.
Materials that do not have a minimum radius are the ones that either take the shape of what is behind them, or are small enough to absorb the curve in their joints.
How each family handles a curve
| Family | Mechanism | Radius tolerance | Watch |
|---|---|---|---|
| Wet-applied (plaster, microcement, render) | Takes the substrate’s shape | Any curve the substrate can be built to | Substrate accuracy; cracking at movement |
| Mosaic and small tile | Segmentation in the joints | Tight | Joint width opens on the convex face |
| Medium tile | Segmentation | Gentle only | Lippage at the edges |
| Large-format tile or slab | None — must be flat or curved to order | Effectively flat | Curved slabs are made to order at cost |
| Thin flexible sheet | Bends within its rated radius | Product-specific | Confirm convex vs concave figures |
| Timber slat on curved backing | Segmentation between slats | Tight, if slats are narrow | Slat width sets the achievable radius |
| Rigid panel, kerfed | Cut relief on the back | Improved, not unlimited | Kerfs telegraph; sheet is weakened |
| Fabric and flexible coverings | Conforms | Any | Support, tension and cleaning |
Numbers are deliberately not given. Minimum radii are product properties that vary by manufacturer, thickness and bending method, and the only reliable source is the current data sheet.
The substrate is the actual problem
The finish cannot correct the backing. A curved wall finished in microcement is only as smooth as the curve underneath it; a faceted substrate produces a faceted wall regardless of how seamless the coating is.
Curved substrates are built either by:
- Curved framing with closely spaced studs or ribs following the radius, then a flexible board
- Flexible board in two thinner layers, staggered, which bends more readily than one thick layer and produces a smoother curve
- Cut formers — profiled ribs at intervals, sheathed
Two thin layers is the common solution and worth specifying explicitly, because a single thicker board will resist the curve and flat-spot between fixings.
Segmentation and faceting
Where the material will not bend, the curve is approximated:
Segmentation breaks the surface into small pieces, each flat, with the curve taken up in the joints. Works when the module is small relative to the radius. Joint width on a convex curve opens slightly at the face, which is either a detail or a defect depending on whether it was designed.
Faceting uses larger flat planes with visible angle changes. Much cheaper than a true curve, and frequently the right answer — but whether it reads as a curve depends on facet width, viewing distance and lighting. Grazing light along a faceted surface reveals every facet, which relates directly to how textured wall finishes behave under the same lighting.
What to confirm before specifying
- Radius, and whether the curve is convex or concave from the finish side.
- Minimum bending radius for the specific product and thickness, from the data sheet, for that direction.
- Whether heat or wet forming is required, and whether the installer can do it on site.
- Substrate construction — framing centres, board layers, achievable accuracy.
- Joint strategy — where segments meet, and whether joint opening is designed or accidental.
- Fire classification for the room’s occupancy, from the product data.
- A mockup if the radius is tight or the material is expensive — see material samples, finish boards and mockups.
When to stop trying
If the radius is below what any acceptable material will follow, the options are a made-to-order curved element, a faceted approximation, or changing the geometry. Forcing a sheet below its rated radius produces a wall that looks fine on handover and fails later, and the failure is not attributable to the material.
For the wider finish shortlist see feature wall materials compared and the interior wall finishes guide.
Frequently asked questions
What is the minimum radius for a sheet material?
It is a product property published in the technical data sheet, and it differs between convex and concave, between thicknesses, and sometimes between dry and wet or heat-assisted bending. There is no reliable general figure by material family.
Can tile go on a curved wall?
Yes, by segmentation — the smaller the tile, the tighter the curve it will follow, because each piece stays flat and the curve is absorbed in the joints. Mosaic follows tight curves; large-format tile effectively does not.
What is kerfing?
Cutting a series of grooves across the back of a rigid sheet so it can bend without breaking. It works, but it weakens the sheet, the kerfs can telegraph through thin finishes, and it needs a substrate that supports the curve continuously.
Is a faceted curve acceptable?
Often, and it is much cheaper. Whether it reads as a curve depends on facet width relative to viewing distance and on the lighting — grazing light along a faceted surface reveals every facet. Test it at the real distance before committing.
Sources
- Building Envelope Design Guide — Whole Building Design Guide, National Institute of Building Sciences Accessed August 27, 2026.