The short answer
Re-bedding the ridge on an average house usually takes a day or two of work on the roof once scaffold or access is in place. A short ridge on a simple semi can be quicker. A long ridge, hips, a steep pitch, hidden damage or wet weather will stretch the job, because mortar cannot be laid in the rain or left unprotected while it sets.
What the work involves, and why that sets the pace
Re-bedding means taking the ridge tiles off, clearing the old mortar from the top of the roof, and fixing the tiles again on a fresh bed. The ridge runs along the very top of the roof, where the slopes come together. The tiles that cap it are bedded on mortar, and over the years that mortar cracks, shrinks and falls out.
The sequence is the same on every roof. The old tiles are lifted and stacked. The cracked mortar and the loose debris beneath it are raked out so the new bed has a clean seat. Fresh mortar is laid, the tiles are set along a straight line and tied back with mechanical fixings, and the joints are finished and struck off. Ridge and hip tiles bedded in mortar also need a mechanical fixing under BS 5534:2014, since a mortar bed cannot be the only thing holding them.
None of those steps is slow on its own. The time goes on doing them carefully over the full run of the ridge, and on getting safely to the top before any of it starts.
What decides whether it is a short job or a longer one
Four things move the timescale more than any others.
- Ridge length. A small terrace has only a modest run of tiles. A long double-fronted house, or a row of connected roofs, means a great deal more tile to lift, clean and set.
- Hips. A hip is the angled line running down an outward corner of the roof. Hip tiles are usually bedded in the same way as the ridge, so a hipped roof adds several runs of work. The hip tiles also need a firm fixing at the bottom, which takes extra time to get right.
- Access. A house with a stepped terrace, a narrow side passage or a roof that rises high above the pavement needs more preparation before work starts. Scaffold, or a tower in the right place, is often what lets the work be done safely and at a steady pace.
- What is underneath. Once the old bed is cleared, we sometimes find the top course of tiles or the battens beneath it in poor condition. Putting that right adds time, but it is better done now than found out by the next leak.
For an honest estimate, the roof has to be looked at. Our free survey records the ridge, hips and verges with photographs, so the scope of the work is clear to you before you decide.
Weather and curing: the part you cannot rush
Mortar is mixed with water and then has to set. Rain landing on a fresh bed washes the cement out of it and weakens the joint, so a ridge is not bedded in a downpour. A light shower can stop work for the day, and a forecast of heavy rain can hold a job back until it passes.
Frost matters too. Frost that reaches mortar still soft can leave it crumbling later, which is why winter jobs are planned around the forecast. The longer guide to re-bedding ridge tiles covers the method in more detail.
Mortar is generally left to set undisturbed. Once the bed is laid, the tiles should not be knocked or walked on while it cures, so the finishing and tidying happen around that. In practice this means the visible work on site may finish before the mortar has fully hardened, and you should not read a quiet roof as an unfinished job.
Hot, dry and windy days bring the opposite problem. Mortar that dries too fast can shrink and crack, so on some days it needs shading or damping down. These are small tasks, but they are part of why a careful ridge job does not run to a stopwatch.
Mortar bed or dry-fix: does the system change the time?
Some ridges are not re-bedded in mortar at all. A dry-fix ridge uses a mechanically fixed system, with no wet mortar bed, and BS 8612:2018 sets the test standard for these dry systems on verges, hips and ridges. Because there is no mortar to set, weather affects it less, and the fixing itself can go quicker. Fitting one still takes care, and the ridge line, the roof's ventilation needs and the profile of the existing tiles all have to suit the system.
On an older house in Bath, a mortar ridge is often the right match for the roof as it was built. Whether the lime content of the mix should be adjusted for the age of the building is a separate question, and our guide to mortar falling from a roof explains why the mortar fails in the first place.
Either way, we tell you which system we propose and why before you commit. The decision follows what we see on your roof, not habit.
Before and after the day on the roof
The visible work is only part of the timetable. A survey comes first, and once you have accepted the fixed price in writing, the date is fixed around the weather as well as your diary. Scaffold may have to be booked for the same slot, and a house in a conservation area or a listed building needs the consent question settled before any tile is lifted.
Re-bedding a ridge is repair work, so it generally falls well inside the Building Regulations threshold for roof work, which is less than 25% of the building envelope and less than 50% of the roof. If you are unsure, B&NES building control or your registered building control approver can say.
At completion the site is cleared and the old mortar and broken tiles are taken away. Keep the photographs of the finished ridge, since a quick look each spring against them shows whether any tile has moved.
If you are weighing up whether the old tiles can go back on, read can ridge tiles be reused. The main service page for ridge and verge repairs sets out the whole range of work at the top and edges of a roof.
