The short answer
Repointing ridge tiles is enough only when the mortar bed underneath is still firm and well keyed, and just the visible joint along the edge has eroded. If the tiles rock, the bed is hollow or crumbling, or there is no mechanical fixing, new pointing hides the problem without curing it, and the ridge needs lifting and re-bedding.
What repointing does and does not do
Pointing is the visible strip of mortar that finishes the joint where a ridge tile meets the roof tiles beneath it. Under that strip sits the bed, a thicker layer of mortar that actually carries the tile. Repointing means raking out the weathered outer joint and filling it with fresh mortar. It renews the face. It does not touch the bed.
That is why the job is so often offered and so often misjudged. If the bed is still solid and keyed to both tile and slope, a tired face is a cosmetic and weatherproofing problem, and repointing is a fair, proportionate fix. If the bed has cracked through, shrunk away or turned to sand, fresh pointing is a thin skin over a weak core. It looks neat for a season and then the tiles carry on moving.
The question is never "does the pointing look old". It is "what is the bed doing underneath it", and that can only be judged by a close inspection.
When repointing is a reasonable choice
There are cases where repointing is the sensible answer, and we will say so.
- The tiles are firm. Press a ridge tile and nothing moves. The bed is holding.
- Damage is limited to the face. The outer joint is eroded, cracked or missing in places, but the bed beneath is dense and tight when probed.
- The ridge is already mechanically fixed. If clips, screws or straps hold the tiles, the pointing is mainly a weather seal.
- The affected stretch is short. A few metres of joint can be dealt with locally.
In those conditions, repointing in a suitable mix is quicker and cheaper than a re-bed, and it makes sense not to take apart a ridge that is working. We repair where repair works.
Even then, the mortar should suit the roof. A hard mix used on soft old tiles can crack them, so the choice of mix has its own answer: see which mortar mix suits a ridge.
Signs that repointing will not hold
Several signs say the bed has failed and a re-bed is the right job.
A tile that rocks, lifts or clicks under pressure has no bond left. A joint that rings hollow when tapped with the handle of a trowel means the bed is separated from the tile. Mortar that comes out in sandy crumbs rather than hard pieces has lost its binder. A gap along the length of the tile, with daylight showing from the loft, means the bed has shrunk clear of the underside.
The age of the ridge counts as well. One trade guide puts the life of a mortar-bedded ridge at roughly 15 to 30 years, with cracking from about 15 years on, though that comes from a single source and the figure depends on exposure and workmanship. A ridge that has been repointed once already, and has started opening again, is telling you the same thing.
The other thing to ask is whether the ridge has any mechanical fixing at all. BS 5534:2014 does not accept mortar as the only restraint for ridge tiles, so an unfixed ridge falls short of current practice however fresh the pointing looks.
Why a re-bed is a different job
A re-bed starts by lifting the ridge tiles, clearing the old mortar from the apex and the tile ends, and checking what is underneath. The top of the roof is then laid with fresh mortar bedding, and the tiles are set back, aligned and fixed mechanically, so they are not relying on the bed alone. Tiles that are cracked or chipped are swapped for matching ones, and the joints are finished and pointed at the end.
It takes longer than repointing, uses more material and needs dry weather, since new mortar will not set well in rain or hard frost. That is why a re-bed costs more and why some roofers lean towards repointing when they should not.
For the full explanation of what happens on site, see our page on dry ridge versus mortar, which sets out the differences between a bedded ridge and a clipped, ventilated one, and the detail on how long dry ridge lasts if you are weighing the two.
Questions to put to a roofer who offers repointing
If you have been offered repointing, a few plain questions will show whether it is the right fix.
Ask whether they have tested the bed or only looked at the face. Ask whether the tiles are mechanically fixed, and if not, whether fixings will be added. Ask what mix is going on and why it suits your tiles. Ask how much of the ridge is being done and what happens to the rest. And ask for photographs of the ridge before the work begins, so you can see what the roofer saw.
An answer that mentions the bed, the fixings and the mix is a good sign. A quote that simply says "repoint ridge" with no detail tells you very little.
When we survey a ridge, we photograph it, tell you what we found and say directly whether repointing will do or a re-bed is needed. Ask too whether the verges are in the same state as the ridge, because both often weather at a similar rate and can share one set of access. It is also worth reading why ridge tiles come loose before you decide.
The rest of the work in this area is listed under ridge and verge repairs.
