Cracks found mid-clean
What if cleaning finds cracked tiles?
The short answer
You are told before anything else happens. When cleaning uncovers a cracked tile, the work pauses at that spot and you receive photographs of each crack with a plain verdict: swap the single tile, repair a run of them, or look wider at the slope. A cracked tile lets water in, so it is mended rather than cleaned over, and the repair is priced in writing before it starts.
Moss can hide a broken tile for years. Here is what happens the moment a clean shows one up, and how the decision gets made.
How a crack shows itself once the growth is gone
Thick moss acts like a bandage. It sits across hairline splits and chipped corners, and it holds a damaged tile in place well enough that nothing looks wrong from the pavement. Once the growth is lifted, the tile underneath tells its own story. A crack running across the width, a corner missing from the bottom edge, or a tile snapped behind the head where it hangs on the batten (the timber lath it is fixed to) all become visible in daylight.
This is why a good clean starts with a look and not with a brush. Each slope is walked before any treatment goes on, and again once the debris is down. Anything that has cracked is photographed where it sits, so you can see it on your phone rather than take our word for it. Those pictures are the same ones that go with the quote if a repair is needed, and they are the reason you never hear a vague line such as 'a few tiles need looking at'.
Why the clean pauses at a damaged tile
Water behaves differently around a crack. A treated, wet roof sheds water down the tile face and into the gutter. A broken tile lets some of it through to the underlay, which is the membrane layer beneath the tiles, and from there to the timber. The cleaning does not cause that, but washing over the crack hides it again for a season and leaves the damage free to spread.
So when a cracked tile turns up, the work pauses at that spot. You are told what has been found, shown the photographs and given a verdict. The sound parts of the roof can usually carry on being cleaned meanwhile. The damaged area gets a decision first: a temporary cover, a like-for-like swap, or a repair carried out before the biocide (the moss-killing treatment) goes on. You choose what happens next, and nothing is added to the job without your say-so.
One tile, a run of tiles or a whole slope
Most finds are small. A single cracked tile is lifted out and replaced with a matching one, taken from spare stock if the roof has any, or sourced to suit. Where several tiles in a row have gone, the cause is often underneath: a rusted nail, a softened batten, or the weight of someone stepping where they should not have. That earns a wider look before more tiles go on top of a weak spot.
If the cracks are scattered across a slope and the tiles are brittle all over, the verdict changes. At that point cleaning is no longer the right job, because the covering itself is reaching the end of its life, and spending on a clean would only polish it. You are told this plainly, with the evidence. Our cracked roof tile answer explains how a patch is judged against a replacement, and where a small repair will do, a small repair is what you are offered.
Whether the repair or the clean goes first
Usually the repair goes first. Fresh biocide on a roof with an open crack can run through the gap, and a tile bedded down while the neighbours are still wet or crusted with debris does not sit as cleanly as it should. Doing the repair on a dry, clear surface gives a neater result and lets the replacement tile settle properly alongside the original ones.
There are exceptions. When the cracks are minor and weather is closing in, a temporary cover over the damaged spot lets the remaining clean go ahead, and the permanent repair follows. Either route is put to you on paper and priced as one sum, and you pick. Our answer on whether cleaning is safe for your tiles covers how the washing itself is done around fragile areas, and why some roofs are better treated than scrubbed.
What a few replaced tiles add to the bill
National guides give a feel for the scale. Checkatrade's roof repair guide, updated in October 2026, puts concrete tile repairs at £90 to £120 per square metre and clay at £110 to £160, exclusive of VAT, and quotes roofers at around £280 to £360 a day. Those are typical UK ranges, not our prices, and a handful of tiles on an otherwise sound roof sits well below the top of them.
What moves the figure is access, the type and age of tile, and whether matching ones can be found. Find out whether a price has VAT and scaffolding built in, because both change the total. The figure from us follows the survey and covers the job in one sum. For the wider picture of what drives the cost of a clean, see what affects the price of roof cleaning, or go back to the roof cleaning and moss removal page.
Related questions
Cracked tile questions
Can walking on the roof to clean it break more tiles?
It can on brittle, ageing tiles, which is why footing is planned before anyone steps onto a slope. Weight goes on the supported parts of the tile, and on very fragile roofs the work moves to a roof ladder, or to long-reach poles from the ground. If a roof is too brittle to walk on safely, you will be told that instead.
Will cleaning make a leaking tile worse?
No. Cleaning does not widen a crack, but it does stop moss from plugging it. A tile that seemed fine because growth was covering the split may start admitting water once the roof is clean. That is exactly why cracks are photographed and fixed at the same visit, or covered temporarily, before rain finds them.