Fibre Reinforced Facade Encyclopedia: Composition
Woven roving is a heavy fabric woven directly from continuous glass rovings rather than from spun yarn, and it is the format used when a laminate needs real structural strength rather than a sealed skin. The rovings run in two directions, warp and weft, so the laminate is strong along both and comparatively weak at 45 degrees to them. Weight for weight it produces roughly twice the tensile strength of chopped strand mat and carries a higher fibre volume fraction.
A 600 g/m² woven roving ply reaches about 45 percent glass by weight, against about 30 percent for a 450 g/m² chopped strand mat ply laid by hand.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Areal weight range | 300 to 1,200 g/m² | 600 and 800 g/m² are the common grades |
| Common weave | Plain and twill | Twill drapes better over curvature |
| Roving linear density | 1,200 to 4,800 tex | Grams per 1,000 metres of roving |
| Fibre orientation | 0 and 90 degrees | Bidirectional; weak on the bias |
| Typical laminate fibre content | 40 to 50% by weight | About 25 to 32% by volume in hand lay-up |
| Cured ply thickness | about 0.6 to 0.8 mm per 600 g/m² | Depends on consolidation |
| Tensile strength of the ply | 200 to 300 MPa | Along the warp or weft direction |
| Bias tensile strength | roughly 40 to 60% of the 0 degree value | The reason ply orientation is scheduled |
| Suits | Structural laminates, infusion, RTM | With a mat interleaf in hand lay-up |
Why a woven format is stronger
In chopped strand mat the strands point in every in-plane direction, so only a fraction of the glass is aligned with any given load. In woven roving effectively half the glass runs along the warp and half along the weft, so in either of those directions roughly half the fibre is fully engaged rather than three eighths of it being partly engaged. The rovings are also continuous across the panel instead of being 50 mm strands relying on the matrix to transfer load between them.
The second gain is fibre content. A woven fabric packs the glass into a dense, ordered array with much less resin trapped between the bundles, so a woven roving laminate carries a higher fibre volume fraction than a mat laminate. Higher fibre content means more strength and stiffness per kilogram, lower resin consumption, and less organic content in the laminate, which helps reaction to fire performance.
Crimp, and the limit it sets
In a woven fabric each roving passes over and under the crossing rovings, so it is not straight. That waviness is crimp, and it costs stiffness: a crimped fibre has to straighten before it carries load, and the crossover points are stress concentrations where the laminate starts to fail. A plain weave, with the tightest interlacing, has the most crimp. Twill and satin weaves float the rovings over several crossings, reducing crimp and improving drape at the cost of a looser, more mobile fabric.
Stitched non-crimp fabric is the modern answer. Layers of straight, parallel rovings at chosen angles are held together by a light polyester stitch rather than by weaving, so there is no crimp at all. A non-crimp fabric of the same weight gives higher stiffness and better fatigue performance than woven roving and is the usual choice in infused structural laminates. Woven roving remains common because it is cheaper, more forgiving to handle and well understood.
Wet-out and laminating practice
Woven roving wets out slowly. The rovings are dense bundles and resin has to penetrate to the filaments at the centre of each one, not merely coat the outside. In hand lay-up this means generous resin on the previous ply, patient rolling with a grooved roller, and enough working time before gel. Dry bundles inside an apparently wet laminate are the characteristic defect, and they show up as low interlaminar shear strength rather than as anything visible.
Woven roving also bonds poorly to itself. Two woven plies laid directly together meet across a smooth, resin starved interface and delaminate readily. Standard practice in hand lay-up is to interleave a 300 or 450 g/m² chopped strand mat between woven plies, which gives a mechanical key and raises interlaminar strength. In closed moulding the picture changes: vacuum infusion and resin transfer moulding push resin through the fabric under pressure difference, wet-out is far more reliable, void content drops below 2 percent and the mat interleaf is often unnecessary.
Where each format belongs
- Chopped strand mat: conformable, isotropic, resin rich skins and barrier plies behind a gel coat
- Woven roving: bidirectional strength and stiffness in the body of a structural laminate
- Non-crimp fabric: the same job as woven roving with no crimp penalty, in infused laminates
- Surface veil: a fibre free resin rich surface layer, not a structural ply
- Unidirectional: all fibre in one direction, for local reinforcement at ribs and fixing points
A typical architectural panel schedule uses a gel coat, a light mat barrier ply, alternating woven roving and mat through the body, and unidirectional or extra woven plies local to fixings and returns.
Verification
Fibre content is confirmed by ignition loss to ASTM D2584 or ISO 1172, which burns off the resin and leaves the glass to be weighed, and converted to fibre volume fraction using the densities of glass and cured resin. Void content is measured to ASTM D2734 and is the honest test of wet-out quality in a woven laminate. Interlaminar shear strength by short beam test to ASTM D2344 is the property that reveals a dry woven bundle or a poor ply to ply bond, and is worth calling for on a laminate qualification sample.
Standards and references
- ISO 2113 (textile glass: woven fabrics, designation) and ISO 4602 (number of yarns per unit length)
- ASTM D578 Standard Specification for Glass Fiber Strands
- ASTM D2584 and ISO 1172 (ignition loss for glass content)
- ASTM D2344 (short beam interlaminar shear strength) and ASTM D2734 (void content)
- ASTM D3039 and ASTM D790 (tensile and flexural properties of the laminate)
- AS 5637.1 and EN 13501-1 (reaction to fire classification of the finished laminate)
Related terms
Questions specifiers ask
What is the difference between woven roving and fibreglass cloth?
Woven roving is woven from heavy continuous rovings and comes in weights of 300 g/m² and up. Fibreglass cloth is woven from finer spun yarn at much lower weights, drapes better and gives a smoother surface, but builds thickness slowly and costs more per kilogram of glass.
Why is chopped strand mat used between woven roving plies?
Woven roving does not bond well to itself across a smooth interface. A mat interleaf gives the plies a mechanical key, raises interlaminar shear strength and helps stop the weave pattern reading through the finished surface.
Is woven roving suitable for vacuum infusion?
Yes, and infusion is where it performs best. Resin driven through the fabric under a pressure difference wets the bundles far more reliably than hand rolling, raising fibre volume fraction and dropping void content below 2 percent.
How strong is woven roving compared with chopped strand mat?
Roughly twice as strong in tension along the warp and weft for the same areal weight, and considerably stiffer, but much weaker at 45 degrees to the weave where mat is uniform.
What does tex mean on a roving specification?
Tex is the linear density of the roving in grams per 1,000 metres. A higher tex roving is a coarser bundle, which builds weight faster but wets out more slowly.
Reviewing a laminate schedule for a facade package? Our fibre reinforced polymer system is documented with published mechanical and fire data. See ShapeShell-RT specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.