fibre cement tile - replacing 12"x24" with 300mmx600mm in terrace

As for the Marley Eternit concrete fibre-board roof tiles, I wouldn’t put them on my dog kennel. Cheap, nasty and used mainly by roofing contractors wishing to replace natural slate with a cheap looking but vastly inferior product. Local councils use the same to save on cost. They are man-made, and regardless of what Marley may state, in my 27 years experience, I have never come across a roof tile as poor. On average, you may get between 15-20 years lifespan out of them, after 7-8 years, they lose their shine as the lacquer starts to deteriorate, and so begins the porous moss issues, then it’s only a matter of time. They are very large tiles, so cover a large area very quickly, hence a lot of roofers like to use them, to keep the cost low and to finish the job as quickly as possible. If a client wishes to have a Marley Eternit tiled roof, I will send them elsewhere, I refuse to, and never will, EVER, put them on a clients roof. The only occasion I have put these on a roof, was so ensure that the adjoining neighbours roof (Marley Eternit, that had been fitted 7-years prior) sat flush with my client, Dr Etherson’s new Crest Planum concrete tiled roof, when we installed an invisible bonding valley to connect the two. The issue was that our roof kicked up, due to the neighbours being installed incorrectly. I approached the neighbour, politely asked her if I could rectify the issue, to which she agreed. I’ve also included an independent link below with a discussion between many client’s who have been very dissatisfied with these Marley Eternit tiles for all the reasons I have mentioned. https://www.diynot.com/diy/threads/problems-with-marley-eternit-monarch-tiles.250444/ And lastly, a project we completed in Middleton Tyas for a client who had been ripped off when a roofer removed his Westmoreland Green slate and replaced them with Marley Eternits, claiming they were real slate. After 12 years, the roof leaked. We installed Grade 1 Spanish slate and brought the £800,000 property back to it’s former glory. It is very rare the rafters in will not support a heavier, much better concrete tile, if Spanish Slate (ideally Grade 1) is out of your budget. Crest Planum are the best on the market right now, an alternative and lighter tile are Forticrete SL8's or maybe the new Marley Edgemere tiles are far superior. Dry bonding valleys or invisible bonding valleys, which I prefer and come in different options from Zinc, Code3 soakers or BS5534 laths, code 3 or 4 wrapped are beautiful for connection slate roofs or different sizes. Never should a bonding valley between to adjoining roofs with differing style tiles be connected by vertical ridge tiles. That is beyond horrific.

Maybe it’s hard to say without looking at the roof and seeing the headlaps etc, if you can’t don't put ridge tiles on the boundary line it’s old fashioned and looked terrible, use a GRP secret gutter bonding strip it’s near tidy, professional and to the untrained eye you won’t notice the join in the two roofs. Regards Frankie BT Roofing Services

You can get smaller fibre cement slates and just put a bonding gutter between yours and next doors roof this means the batons don't need to line up

Yes you can. You will probably need more slates than was originally on the roof and possibly some double width slates to help merry in the courses if needed.but it shouldn't be a problem at all.

You can use a bonding gutter where you're property adjoins the neighbouring property, it will seperate the roofs and allow you to change slate size/ batten gauge. But if the budget allows, you should always go for natural slate.