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(Andrew Gabriel) wrote in message ...
In article ,
(N. Thornton) writes:

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface

I use 1:1:6. The render isn't the facing surface indoors anyway
(I assume you will skim it afterwards).

I've done some 1:1:6 rendering now, and I have to agree with you
there, its plenty strong enough.

strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

In lime mortar, lime reacts with CO2 to grow a crystal across the
crack, and this self healing provides some movement tolerance. I'm not
sure if there may still be a bit of this action with a lime cement
mix, but the lime can still meet the CO2, as the plaster would crack
at the same time, so it seems quite likely, unless perhaps you know
about all this in greater depth.

It's silly to point if you're about to render. The unpointed
surface will provide a much better key for the render, and if
you are applying the right pressure, the gaps will be filled
anyway. Do remember to PVA the brick.

First it depends on the depth of the gaps and how much pressure is
applied when rendering. Second it literally takes about 2 minutes to
repoint quite a big area with a glove. Its just a way to ensure you
get max strength there. It doesnt always matter, often doesnt in fact,
but Victorian buildings are sometimes marginal and those ones need any
strength they can get. With those ones filling the mortar gaps fully
does matter, so I think its worth 2 minutes to avoid a risk.

Regards, NT