On 22/04/2018 12:07, Dave Plowman (News) wrote:
In article ,
Bill Wright wrote:
On 21/04/2018 22:22, Harry Bloomfield wrote:

He didn't need to hack off, just 'butter' a bit over the exposed tile
edges.

I've been on hundreds of roofs where that's been done and the new mortar
has come off and slid down the roof. The only way to do ridges is to
take the tiles right off, remove all the old mortar, lay a new bed, then
point up.

And if you must use mortar, use a lime based one which allows more
movement. You can buy it ready mixed, and the costs low as part of the
overall cost of doing the job.

Depends on what the tiles are made off. Marley Modern concrete
tiles are better with a slightly stronger mortar mix because they
are pretty strong anyway. If you mix a bit of cement dye in the mix
to make it dry greyish, then that compensates for the extra
cement anyway.

There are a few extensions near me with these tiles, where a
weak mortar mix was used, which dried an awful sandy colour, unlike
the original roof, and the frost is making a couple of
them fairly tatty after only a few years.