How you know you have got one
Sometimes it is obvious - a tile in the garden after a windy night. More often it is not. Tiles slip a few inches rather than falling, and from the pavement a slipped tile just looks like a slightly wonky line in the course. Stand across the road and look along the slope rather than at it, and the shadow gives it away.
The other tell is inside. A tea-coloured ring on a bedroom ceiling that stops growing between wet spells, damp on the top of a chimney breast in the loft, or a musty smell up there in summer. By the time a stain appears downstairs the water has usually been getting in for a while and has found something absorbent to sit in on the way.
Why they slip in the first place
Old tiles were hung on timber battens with a nib, and only every few courses were nailed. The nails are the thing that fails. Around the Herne Bay seafront, where the air carries salt off the estuary, plain steel nails can be little more than orange dust while the tile above them still looks perfect. Elsewhere it is simply the batten softening where water has been tracking down it for years.
What I do about it
The repair itself is not complicated, but the diagnosis matters more than the tile. I lift the courses above, check the batten is still sound enough to hold a fixing, look at the state of the felt in the gap, and re-hang the tile with a clip or a copper nail rather than a steel one. Then I look at its neighbours, because a tile rarely slips on its own - if one nail has gone, the ones either side of it are the same age.
What I will not do is bed a slipped tile in mortar to make it stay put. It works for about two winters, it stops the tile moving the way it is designed to, and it makes the next repair worse. If you have had that done before, I will usually take it back out.
What changes the price
I price after I have seen it, not before, because these four things move the number far more than the number of tiles does:
- Where on the roof it sits. A tile two courses up from the gutter is a different afternoon to one beside a chimney or down in a valley.
- Whether I can get a ladder to it. Rear slopes over a conservatory, or a terrace with no side access, sometimes need a tower putting up.
- The state of the battens. Sound batten, quick job. Rotten batten, and the repair has to keep widening until it reaches solid timber.
- What the tile actually is. A stock concrete one I can pick up locally. A handmade clay peg takes finding.
Kent clay, and why it is worth keeping
A lot of the older housing between here and Canterbury still wears clay peg tiles, and there is a strong argument for repairing rather than replacing them. They are small, they are individually hung, and a broken one is genuinely a five-minute swap. They also weather in a way concrete never manages - part of why a Victorian roof around Faversham looks right and a re-covered one next door often does not.
The catch is that they are brittle when cold and unforgiving of being walked on. If your roof is pegs, be wary of anyone who wanders about on it in work boots to "have a quick look" - you can easily end up paying for the tiles they cracked getting to the one that had slipped.