Is mortar bedding for ridge tiles still allowed?

You may have heard that mortar on a roof has been outlawed. It has not. No rule says a roofer cannot bed a ridge tile in mortar, and thousands of repairs are carried out that way each year. The change is about what holds the tile in place.

The standard that covers slating and tiling is BS 5534. When it was revised in 2014, the pulling strength of a mortar bed was judged too weak to trust as the sole fixing for ridge and hip tiles, and the practice of bedding with nothing else, which had been common, came to an end. Bedded tiles and fittings now carry a mechanical fixing too. The mortar still has a job: it fills the space, seals the joint against weather and sets the tile at the right height. But the fixing carries the load in a gale.

Beneath a mortar-bedded ridge, expect stainless steel screws or nails through the tile, or a clip, or a strap holding the tile to a ridge batten or to the timber below. The detail depends on the tile and the roof, and the maker's guidance for the particular tile applies. The mortar is then placed over and around it, so the fixing is hidden and the ridge keeps its traditional look.

For hip tiles the same rule applies, with the added support of a hip iron at the foot. Hips are steeper than ridges, so the load on each fixing is greater.

On a roof that was bedded in mortar years ago and has no fixings, nothing has to be done in law on the day a standard is revised. But when a ridge needs repair, the sensible moment to add them is during the work, because the tiles are already lifted. A repair that simply refills the joints leaves a ridge secured to the standard of its time, not of today.

That is why a quote for ridge work should say how the tiles will be fixed, not only that they will be re-bedded. Ask what goes through or around each tile, the material, and the spacing between the fixings sit. A clear answer tells you the work has been thought through, and an evasive one tells you to ask again.

A dry-fix ridge replaces the mortar with a set of purpose-made parts: ridge tiles or plastic ridge units screwed or clipped to a batten, with a vented roll or strip beneath that closes the gap and still lets air pass. Nothing in the system can crack, shrink or drop into the gutter, since no mortar is involved. BS 8612:2018 is the specification these systems are tested against, and a product that has not been through those tests cannot claim to meet it.

Both routes can give a sound ridge. What separates them is upkeep. A bedded ridge will need its joints looked at every so often, while a dry ridge needs its fixings and vents checked after storms. Neither is a fit-and-forget finish, and any roofer who says so is selling.

Dry-fix is not automatically better. It suits most modern tiled roofs and many repairs, but on a house in a conservation area or a Cotswold-style stone slate roof, a visible plastic unit may look out of place, and mortar with fixings can be the better choice. Our page on the dry hip system explains how the hip is dealt with, and dry verge systems covers the equivalent for a gable edge. On a protected building, put the question to your local council's planners before the look of the ridge is changed.

Many people ask the question after seeing cracked mortar from the garden, and the worry is understandable. Cracks do not by themselves mean a ridge is unsafe, but they do mean water can get past the joint. Our page on ridge mortar cracking explains what causes it, which cracks are cosmetic and which need action.

Mortar also varies: the mix, the sand, the colour and how it was cured all change how well it lasts. A repair done with the wrong mix can crack again within a couple of winters, which is why a good roofer matches the mix to the tile and the exposure of the roof.

Then there is the cost of reaching the work. The ridge is high, and on most two-storey houses scaffolding is needed. It is worth reading how that works on our page about scaffolding for ridge repairs, because for a short ridge the access alone can take up much of the budget. With ridge prices in hand, check that the total allows for the tower and for VAT.

If your roof has mortar bedding and it looks sound, you do not need to rip it off to meet a rule. If it is cracked, loose or missing in places, ask for a repair that puts a mechanical fixing behind the mortar, or for a dry ridge if that suits the house. For the standard itself, the full guide to BS 5534 ridge fixing goes through what it says and why it was revised, and the main ridge and verge dry-fix page shows the rest of the range.

Send a photograph of the ridge from the ground, or arrange a survey. What returns to you is a set of pictures of the ridge as it stands, then a written quote for work in proportion to the fault. Our own labour is guaranteed in writing for a full decade, and rubble and offcuts are taken away.