Martin Bonner wrote:
The Natural Philosopher wrote:
wrote:
Lime or cement mortar?
I won't bother to go through pickling out the things that are plain
wrong, and those that are simply exaggerated through prejudice.
PLEASE do. Most of the OP seemed very reasonable to me, but I would
love to hear opposing views. (I have to say that the paens of praise
for the visual appearance of lime mortar struck me as over-egging the
pudding).
Suffice to say there are good reasons why Portland cement is used rather
than lime, these days.
To be fair, the OP did start:
This is specific to old buildings, and walls of similar construction.
With a new build, hard-fired bricks, DPC, and extensive foundations, a
lot of the arguments for lime go away.
As someone has already said, there is no mention of hydraulic lime. For
example, brick dust acts as a pozzolan (as does any material that has
previously been baked, volcanic ash, iron oxide dyes etc.) and this
causes the mortar to set in varying degrees. This aspect seems to be
shrouded in mystery (I suspect deliberately). How much of the alleged
self healing property is lost, and how does it then differ from cement?
I doubt the Victorians could build houses at the rate they did without
some form of set taking place.
IME, if you can't protect ordinary lime mortar from the weather, shallow
applications such as pointing will be washed away by the first rainfall.
Hanging damp sacks all over the place doesn't seem that practical to me.
The other issue is the degree to which modern additives have improved
the properties of cement. At a basic level I'm sure we're all familiar
with how pva reduces cracking and doubtless there are more sophisticated
products around.
There is of course a large element of brown eggs and bicycles about all
this too. Right on types who want to turn the whole thing into an art
form and congratulate each other on their good taste via various
conservation websites.