On 7/29/2017 2:31 PM, Dave Plowman (News) wrote:
I've got a Victorian semi, and the brick walls go above the roof. On top
of those walls is a coping of pre-cast concrete lengths - each one a
couple of feet or so long - replaced along with the roof some years ago.

At the end of this wall (front of the house) is a typical Victorian cast
stone. Which included a short length of this coping stone - but all in
one, so would tend to retain the others. This stone is three brick courses
high (at the front) and extends about 2.5 ft back into the wall.

And is spalling badly. One worse than the other - and of course it's the
one between the two houses, on the party wall.

When the roof was replaced about 30 years ago, the roofers rendered this
stone - and that has all fallen off, bit by bit. Luckily no-one was
injured by the falling chunks.

The house is scaffolded for painting, so I have reasonable access. But
only on my side of this central stone.

In an ideal world, I'd remove it. Make up some shuttering and cast up a
new one. But I don't fancy doing any damage to next door's roof - and I
can't get access to that side from the scaffolding anyway.

I've got a load of lime mortar made specifically for fixing this sort of
stone. It would be possible to fix shuttering to the existing stone to
remake the coping part. But just how well would the lime mortar hold?

I'll take some pics and put a link to them if it would help.

Sounds like a plausible idea. The other thing you might think about is
ways to improve the keying. For example you could drill some holes in
the face to be repaired, insert plastic wallplugs, and then put in some
screws protruding a certain amount from the surface. I think I would use
stainless steel screws.

Are you talking about pure lime mortar, or one containing some cement as
well? My suspicion is that while simple lime/sand is fine for repointing
and filling cracks, you might want something a little bit stronger here.