In article ,
"keith_765" writes:

"Andrew Gabriel" wrote in message
. ..
Didn't get to the flaunching today -- that will be tomorrow, or
Wednesday if I need to buy more tiles.

I would like the tiles to overhang the flaunching slightly, so
that even if the tile to flaunching bond breaks, the water still
goes into the gulley. However, that makes it really hard to get
a good finish under the tile edge. The way it was done was the
flaunching was brought up in front of the cut tile edges and
made level with the tile top. This may be because, having removed
the flaunching, I can see the cut tile edges are not in a very
straight line, which the flaunching was making up for.

Still thinking this one through...

Pointing to a tiled valley can course more trouble. Before I comment I
would like to know, which type of tile is on the roof, concrete single lap
interlocking or plain tiles, and is the valley lined with Lead, GRP or
concrete valley trough. By the way 4 to 1 is useless for this type of work.
2 to 1 stiff mix and PVA if you are leaving the old mortar in. BS 5553
states " Open cut lead valley's with plain tiles should not be bedded or
pointed"

I called up Lafarge's helpline, and the chap there was very helpful.
He said to use 3:1, and sharp sand for best result. I asked about
PVA (which I do normally add when I want a strong mortar) and he
wasn't happy about that in mortar exposed to such moisture. He said
if I really wanted a bonding agent, use SBR(?). I commented that I
had waterproof PVA, and he was happy with that (he might have said
that is SBR -- didn't fully catch the comment). He also said to
coat the sand areas on the plastic gully with a slurry of
cement/waterproof-PVA/water in a 2:1:1 ratio to make the mortar
bond well, and apply the mortar whilst the slurry is still tacky.

Anyway, I did one side of the gully. You know that nice feeling you
get when you're doing something and it's going perfectly? Well, I
just wasn't getting that. Mortaring in tiles further up was causing
the ones lower down to move and come unstuck. I had visions of this
last part of the job still leaving me with a leaking roof, screwing
up all the re-felting, replacement of battons and tiles I had done.

In the morning when it had set, the mortar did look better, and the
tiles did all look stuck, but I wasn't going to try tugging on one
to see. I decided to call a roofer to mortar the other side and
redo the side I had done. Roofer came to have a look and said my
side was fine and didn't need redoing. He's going to do the other
side for me though.

Roof was just tested with a torrential downpour. I was up in the
loft looking for leaks, but not a drip to be seen, and that's with
one side of the valley still unmortared. I guess that's a good
sign at least.

I took lots of pictures whilst I stripped the roof around the
valley off, and redid it. When I get a chance, I'll put them up
somewhere. They also turned out to be invaluable when I was retiling
afterwards, as a reference to how it had been tiled before I started.

--
Andrew Gabriel