the mortar verge on one gable of my slate roof has failed already (cracked in multiple places and seperated from undercloak) weeks after it was finished. I suspect the others are soon to follow. This is one area I neglected to give enough thought and just went with mortar verge as that's what I'd seen pretty much everywhere else. I now realise there are shortcomings with a mortar system and I think I read that the NHBC will only now warrant a dry system, presumably becuase of too many failures. The roofer has offered to re-do the failed verge (I suspect that means chopping out the mortar and re-packing) but I wonder if I should instead have them all re-done with a dry system. It will cost me, but so will having them all re-done in 10 years when they've all failed and the battens have started to rot.

Has anyone experience of any dry systems that look good with natural slate? I've seem some horrid looking dry systems used with concrete tiles but, looking online, natural slate systems look a bit more discreet. One which caught my eye was the permavent easyverge, this sits under the slate and uses rubber fins to make a water seal so you can still see the edge of the slates, others seem to enclose the edge of the slate and box it in with an internal drainage channel down to the gutter.

The verge detail currently is slate, batten, cement board with mortar fill, oversailing barge board by about 50mm.

suggestions appreciated

I recently had my roof retiled with natural slate. We used a hybrid approach. You can use wet mortar but mechanically fix rubber sealed screws between each slate. This is the same, conceptually, as dry ridge, since they cannot slide off with the screws in place and is permitted by the regs. However, you can see the little silver screws, which isn't as aesthetically pleasing as a lovely thin layer of mortar (but thats not an option as mortar alone is not permitted). However, it doesn't look bad at all and once its up you never look at it again.

Dry ridge also looks fine - though some systems are better than others, so worth researching a bit. The advantage of dry ridge, I think, it the ventilation it introduces at the ridge line, so you get a good chimney effect on the air movement. If I did it again I would use dry for this reason

So dry fix is literally like a rubber strip that goes over your hips and ridges, and then the tiles sit on it, and clips hold them down.

Mortar fix is just tiles sitting on a bit of mortar. Then in between each tile, in the area where the mortar is like with bricks, is a screw that screws into the wooden batton. The way to think about traditional hips is that the only thing stopping them coming off the building is the hip iron at the bottom - in other words they slide down the hip. Thats why a screw between each one is a good way to fix them. Most are too heavy to be blown by wind, and cant really slide off any other way. Dry was invented, as I understand it, because the mortar does not a lot on natural slate, since it cannot bind very well, hence relying on hip irons.

I would recommend getting a roofer in your area to give you examples of both systems. I am afraid my scaffolding is down so I cant give you a photo

In my view slates do not want or need any mortar or undercloaking, far far better off without.

Cloakers will stop rain tracking back in, but please note that undercloaks generally cause this too :)

a) brick wall, stop battens immediately behind the brick, 100mm wide, slates are wide enough to carry over, half slates are wire tied to whole slates. But note half slates at the end is very poor practice and slate and a half should be utilised.

b) stud wall is with rain screen simply add a barge or rail at the top, stop the battens behind that and slates sit dry on top of it.

Undercloak is anything that sits under a tile/slate at the verge, (insane in my book) generally filled with cement mortar.

Cloaker is like a soaker but hangs down over the verge formation, generally made of lead or ali, possibly in the future plastic, akin to a cloaked verge tile where these do not exist for slates

To see what I do with plain tiles see :- http://readinguk.org/draughtbusters/wp-content/uploads/2017/01/P1040134.jpg

Some verge systems are grp and this is also used for flat roofs so. Ought to be durable

But nothing as durable as nothing as there is nothing to it to go wrong.

Not for me.