Custom Curved Polyurethane Faux Beams for Barrel Vault Ceiling Structures

Understanding barrel vault geometry

A barrel vault is a continuous arch — semicircular or segmental — that spans the length of a space. In cross-section, it's a simple arc; in plan view, it's a rectangle. The vault can be a true semicircle (180 degrees) or a segmental arch (less than 180 degrees, typically 120–160 degrees). Segmental arches are shallower and work better in rooms with limited ceiling height.

The radius of the vault is determined by the room width and the desired arch height. A 6-meter-wide room with a semicircular vault has a radius of 3 meters and a crown height of 3 meters above the spring line. A segmental vault with the same width might have a radius of 4 meters and a crown height of 2.2 meters. The shallower segmental vault is more practical in most modern buildings with standard ceiling heights.

The spring line is the point where the curved vault begins — where the arc leaves the wall and becomes the ceiling. The crown is the highest point of the vault. The haunch is the zone between the spring line and the crown, roughly the middle third of the arc, where the vault is most visually prominent.

Transverse rib layouts

Transverse ribs run perpendicular to the length of the barrel vault and form a series of evenly spaced arches across the ceiling. This is the most common barrel vault beam layout in modern interiors.

The ribs can be evenly spaced (creating a uniform, rhythmic ceiling) or varied in spacing (creating a hierarchy that draws the eye to the center or to a specific zone). Uniform rib spacing works well in contemporary interiors. A series of evenly spaced ribs across a barrel vault reads as a clean, disciplined ceiling. The spacing is typically 600–1,200 mm on center, depending on the room length and the visual weight of the beam profile.

Varied spacing creates a focal point. Designers sometimes place ribs closer together near the center of the vault (where the eye naturally rests in a room) and space them farther apart near the walls. This subtle emphasis makes the room feel taller and more focused at the center.

For very long barrel vaults (over 8 m), we sometimes design the ribs to converge slightly toward the center, enhancing the perspective and making the space feel more intentional. This effect is subtle but powerful in large rooms.

The rib profile should be consistent from spring line to crown. We do not recommend tapering the profile as it rises through the vault — the taper reads as an error rather than a design choice.

Longitudinal beam layouts

Longitudinal beams run along the length of the vault, following the curve from spring line to crown. These beams don't create a ribbed ceiling — they create a timber-lined vault where the beams are parallel to the walls and follow the arch profile.

Longitudinal layouts are less common in contemporary interiors but appear in Mediterranean, Spanish Colonial, and Tuscan-inspired designs. The beams are typically spaced 800–1,200 mm apart, and the space between beams is either left open (showing the plaster or concrete of the vault) or filled with a flat panel.

The advantage of a longitudinal layout is that the beams follow the curve continuously from spring line to crown without any splicing. A continuous beam is more visually coherent than short transverse ribs and reads as a more deliberate architectural gesture.

The disadvantage is that the beams are longer and more expensive to produce and ship. For very long rooms, the beams may need to be spliced at mid-span, which requires a hidden splice block.

Mounting on curved vault surfaces

Mounting beams on a curved surface requires a different approach from mounting on a flat ceiling. The beam has to be aligned with the curve at every point along its length.

For transverse ribs, we supply curved mounting blocks that are pre-engineered to the vault radius. The blocks are attached to the structural ceiling at each rib position, and the beam drops over the blocks and locks into place. The blocks are concealed inside the beam and not visible from below. The spacing of the mounting blocks matches the rib spacing.

For longitudinal beams, we supply curved mounting channels that follow the vault curve. The channels are attached to the structural ceiling, and the beam slides into the channel from the end. The channel holds the beam at the correct radius and prevents it from sliding or twisting. The channels are concealed inside the beam and not visible from below.

Both systems allow for thermal movement. The beams expand and contract with temperature changes, and the mounting system accommodates the movement without transferring stress to the structure or cracking the finish.

Splicing for long spans

For barrel vault ribs longer than 4 m, beams are shipped in two pieces with a hidden splice at the center. The splice is a pre-finished PU block that fits inside both beam halves, aligning them and locking them together. The splice is concealed within the beam and not visible from below.

The splice location is determined by the layout drawing. We typically position splices at mid-span between mounting blocks, where the bending moment is lowest and the aesthetic impact is minimized. Each splice location is marked on the beam so the installer knows exactly where to join the pieces.

The splice installation involves drilling two access holes in the inside of the beam, inserting the splice block, securing it with screws, and filling the access holes with color-matched plugs. The process takes about 20 minutes per splice and produces a joint that is invisible from below.

Beam profile selection for vault applications

The beam profile determines the visual weight of the rib. For barrel vaults, we typically recommend medium-scale profiles (6x8, 8x8, or 8x10) because they read clearly at normal viewing angles without dominating the vault form.

Larger profiles (10x10 and above) work in very tall spaces — crown height over 4 m — where the beams will be viewed from below at a steep angle. In a tall room, larger beams are proportional to the space. In a standard-height room, they would crowd the visual space.

Smaller profiles (4x6 and 6x6) can work in contemporary minimalist interiors where the ribs are meant to be a subtle texture rather than a dominant architectural element. With smaller profiles, the spacing should be tighter (400–600 mm) to maintain visual presence.

For barrel vault applications, smooth-profile beams are most common because the clean lines echo the smooth arc of the vault. Hand-hewn or rough-sawn textures work in rustic spaces where the vault should feel more organic and less formal.

Finish options for vaulted ceilings

Barrel vault beams are finished to complement the vault surface. The most common approach is to finish the beams in a warm timber tone and leave the vault surface in a neutral white or cream. This creates a clear hierarchy: the beams are the architectural element, the vault is the canvas.

For more dramatic interiors, the vault surface itself can be finished in a complementary tone — painted in a soft blue, sage green, or warm terracotta — and the beams are finished in a darker tone that contrasts. The contrast makes both elements more legible and creates a more colorful, characterful space.

Multi-tone finishes work particularly well on barrel vault ribs because the grain catches light differently at different angles as you move through the space. A multi-tone beam at the crown of the vault catches the most light and reads most dramatically. The same beam at the spring line, where the light is softer, reads more quietly. This variation is inherent to the material and adds life to the ceiling.

Send the vault dimensions (width, length, crown height, radius, and arc angle), the beam layout (transverse or longitudinal), the beam profile, the spacing if applicable, and the color reference, and we'll return a layout drawing, a mounting detail, a splice plan, a sample chip, and a quotation within seven business days.