Grit in your gutters from the roof tiles: what it means

Where the grit comes from

Concrete tiles: normal wear

Concrete tiles change as they age. Wienerberger, a major tile manufacturer, says that "the majority of concrete roof tiles manufactured around the world are surface treated", and that their colour "will eventually fade over time". Some ranges have a deliberately granular finish. Marley, one of the UK's biggest tile makers, says tiles and slates "gradually change in appearance over time through the action of natural weathering", through rain, sunlight, dust and growth.

So a little grit, with tiles that look faded but are otherwise whole, is what an older concrete roof does. On DIYnot, a homeowner who noticed "a fair amount of the granular tile grit coating in the gutters" asked whether it mattered. A roof cleaner replied that "the tile is still waterproof as its made of solid concrete". That's one tradesman's view on a forum, but it matches what the manufacturers describe.

Clay tiles are different

Clay tiles don't fade the way concrete does. Wienerberger notes that clay colour doesn't fade over time. So if you've got a clay roof and a lot of grit in the gutters, look elsewhere first: the mortar on the ridge and verges, or a flat roof or extension draining into the same gutter.

Ridge and verge mortar: the one to check

On many roofs, the ridge tiles along the top and the tiles at the gable ends are bedded in mortar. Over the years, rain and wind wear that mortar away, and it washes down into the gutters as sandy grit.

Marley explains that displaced ridge tiles in high winds relate "specifically to use of mortar to bed them", and that "environmental conditions such as driving rain and wind" can "erode and dislodge the ridge from its bedding". It suggests that where ridges have already come loose, replacing them with a dry ridge system may be sensible, because mortar-bedded ridges can't easily be reinforced.

Signs to look for from the ground: gaps under the ridge tiles, ridge tiles out of line, mortar missing along the gable ends, or pieces of mortar on the ground or in the gutters.

When grit is a warning sign

• The grit arrived suddenly after the roof was jet washed. Marley says high-powered jet washes can "damage the surface of the slate or tile".
• You can see tiles that are cracked, flaking or crumbling at the edges.
• There are gaps in the ridge or verge mortar, or ridge tiles have moved.
• There's damp in the loft, or daylight showing through.

If any of these apply, have the roof looked at. If none do, the grit is most likely normal wear, and the job is just to keep it out of the downpipes.

Why grit still needs clearing

Grit is heavy, and it settles in the bottom of the gutter where it mixes with leaves and moss into a dense sludge. It washes towards the outlet and can collect in the bend at the top of the downpipe. Even if the tiles are fine, the gutters need clearing.

How we deal with it

When we clear your gutters by hand, we look at what the grit is and where it's coming from. We photograph the ridge, verges and roof slopes, so you can see whether it's normal wear or mortar that needs attention. If the ridge needs work, we'll quote for it separately, including a dry ridge system where that's the better fix.

Written by Hawkes Roofing, roofers based in St Albans who clear gutters and repair roofs across Hertfordshire, Buckinghamshire and north-west London. Last reviewed 26 October 2026.