Incorrect specification of Hyrdaulic limes

[Anonymous]

Hi there

When I needed the front of my timber-framed house completely replastered in lime, a local "specialist" insisted on supplying moderately hydraulic St Astier. As a result the whole thing was done in that using a three coat system. At the time I did not know about lime putty.

The work looks very nice but the plaster is absolutely rock hard and limewash won't adhere to it properly. I have since read that Hydraulic limes have no real place in conservation work unless you're restoring a harbour wall for example.

Pretty much all the well known lime suppliers stock Hydraulic limes and I wonder how much of it is being used incorrectly, ie instead of putty.

As far as my house goes, one small crack has already appeared in the plaster and I suppose over the years I will replace blown areas with softer non-hydraulic mixes. I just hope that damp will not cause a problem in the meantime.

Any comments anyone?

Don

 

[Anonymous]

>Hydraulic limes have no real place in conservation work
That's a bit of an extreme position. Different people will have different views.
I can't see any good reason why limewash wouldn't adhere to render made with hydraulic St Astier lime. I suspect there was something else amiss.

 

[Anonymous]

hydraulic lime should only be used where a chemical set as opposed to a carbonation set is required. not suitable for a render in my opinion...... if the surface is finished with a steel float then limewash will not adhere.....

start again.

 

[Anonymous]

I rather suspect that many 'specialists' who use hydraulic do so because it's easier to use - not because of its suitability... they possibly hope the client has no idea really.

I agree - not in general something I'd use apart from special situations. I know that historically some lime would have been feebly hydraulic, but we now have more control over what we use and a non-hydraulic is better if you want a breathable structure.