Moss

Moss seldom grows directly on the fabric roof of a convertible car, as it prefers shade and a substrate to grow on. If you have a green roof, it is more likely you are seeing algae and lichen.  We do sometimes see pavement moss growing on  seams and edges where dirt has built up. We have also seen grass and clover grow in these areas!

A synthetic cabriolet roof is a sterile environment, so if anything is growing on your roof, it is growing on dirt that has built up over time.

What it means

Moss is the soft, cushiony green growth you often see where a car has been parked under trees or left damp and dirty for long periods. Unlike a thin film of algae, moss grows in little tufts or clumps. On cars it favours fabric and mohair soft tops, window rubbers, gutter trims, panel gaps and any ledges where dirt and moisture collect. It has tiny root-like structures that anchor into the texture of the surface, so it does not simply wipe off.

Why it matters

• Makes the car look badly neglected: Mossy roofs and rubbers are a clear sign a car has been left outside and poorly maintained, which can worry buyers and insurers.
• Holds moisture and grime: Moss traps water and dirt against fabric, rubbers and seams, which is not good news for stitching, membranes or paint edges underneath.
• Can encourage leaks and staining: Persistent damp around seams, stitches and seals can help water creep further in and leave marks that are hard to remove.
• Harder to remove than simple dirt: Because it is a living growth that is anchored to the surface, moss usually needs patient, staged cleaning rather than one quick scrub.

Where you’ll see it

You will see moss most often on fabric and mohair convertible roofs, especially around the edges, stitching lines and folds that stay damp. It also appears on window rubbers, in roof gutters, around tailgate channels, under wiper arms and in trim joins that rarely get cleaned properly. Inspection and detailing reports may mention moss on soft top and rubbers, heavy moss growth in gutters or moss around window seals and roof edges.

Context

Moss is part of the same family of biological contamination as algae, lichen and mould, but it is thicker and more three-dimensional than simple green film. On cars it tends to favour shaded, damp areas that are not hit hard by normal washing. Proper treatment usually involves pre-soaking, gentle agitation and repeated rinsing, sometimes over more than one session, followed by appropriate protection such as fabric roof proofer or rubber and trim dressing. Aggressive scrubbing or very harsh chemicals can damage the underlying material long before the moss finally lets go, so technique and patience are just as important as the products used.

Common mistakes

• Attacking moss with very stiff brushes, scouring pads or pressure washers at close range, which can damage roof fabric, stitching, rubbers and paint edges.
• Using strong TFR, bleach or household chemicals in an attempt to burn it off, leading to bleaching, streaking and weakened materials.
• Expecting a single quick wash to cure years of moss growth, instead of planning a gentle, staged cleaning process and follow-up protection.
• Leaving moss in place on soft tops, seals and gutters for years, allowing it to hold moisture, stain the surface and make eventual restoration harder and more expensive.

Written by Danny Argent. Last updated 03/12/2025 17:07