Why Ridges Fail
Traditional ridges are bedded in a sand-and-cement mortar. Over time the mortar shrinks, cracks, and eventually breaks its bond with either the ridge tile or the roof covering below. Once that bond fails, the ridge tile starts rocking in the wind. Over a few seasons the rocking wears the mortar away, water starts getting underneath, and eventually one ridge lifts off in a gale. At that point you've got an open hole at the top of your roof — and the wind gets under the neighbouring ridges much more easily, so more failures follow.
The other failure mode is that the mortar stays intact but water gets between the ridge tile and the covering below (because the bedding was thin to start with, or because the top course of tiles or slates has sagged over the years). You get slow leaks that run down the underside of the ridge and drip through the ceiling at the apex of the loft.
Re-bedding vs Dry Ridge
There are two fundamentally different ways to fix a failing ridge. The old-school answer is to take the ridges off, clean them, and re-bed in new sand/cement mortar. This works, but it's only buying you another 15 to 20 years before the same failure cycle starts over. A lot of roofers still do this because it's quick and the labour charges more than the materials.
The modern answer is to convert to a dry ridge system. The ridge tiles sit on a continuous weatherproof roll (a flexible breathable flashing that seals between the ridge tile and the roof covering below), and each ridge is mechanically fixed down to a batten with stainless steel clamp brackets. No mortar anywhere. The result is a ridge that doesn't wash out, doesn't blow off, and doesn't leak — essentially for the life of the roof.
Dry ridge systems like Klober Permovent, Marley RoofPro and Ubiflex DRS all meet the current British Standard (BS 5534:2014) which actually requires all new ridge work to be dry-fixed. Mortar bedding on new installations is no longer compliant.
What It Costs & Takes
A full dry ridge conversion on a three-bed semi — typically 8 to 10 metres of ridge — takes a day with ladder access, two days with a mobile scaffold tower. Typical cost is £800 to £1,500 including a new ridge roll, clamp fixings, and taking up and reinstating existing ridge tiles (unless they're broken, in which case we'll quote for replacements too).
Full mortar re-bedding is cheaper — £400 to £700 for the same run — but we'd only recommend it for listed buildings where conservation officers specifically require lime mortar bedding. For any normal house, dry ridge wins on cost over a 20-year period once you factor in the time between re-bedding cycles.
Associated Work
While we're up at the ridge, it's worth looking at a few things that often need attention at the same time. The top course of tiles or slates just below the ridge gets the least protection from the ridge overhang and often shows the first signs of weathering. Cracked or slipped tiles in the top course can be replaced as part of the ridge job. Flashings where the ridge meets a chimney are another common area for simultaneous work. And we always check the ventilation at the ridge — modern dry ridge systems include ridge ventilation as standard, which can retrofit proper loft ventilation to houses that were never detailed for it.
