NHL3.5 render - mix not as workable as lime putty?

[inwood]

I'm about to render the corner of my building (at some point the stone work at the corner of the gable end has been replaced with brickwork which is in a very poor state due to being previsouly covered in a cement render).

I've been mixing up a test batch of render (3:1 NHL3.5) and found the mix appears to be quite loose/dry. When I take some off the hawk it falls into pieces rather than staying together. Adding water just seems to make it sloppy rather than the nice sticky stuff I get with lime putty.

The sand I'm using is a well graded washed sand which has already been excellent for plastering with the lime putty.

Any ideas why the NHL mix doesn't appear to be as workable? Should I mix the water/NHL3.5 to a paste before mixing into the sand? My alternative is to use some putty instead of the NHL and gauge it with some Metastar.

Any suggestions welcome.

 

[Nemesis]

Why are you using hydraulic? Any sound reason?

 

[inwood]

The corner is exposed, in a windy location (even when there's no wind as the buildings around channel any air movement around this corner) and I'd like to get a quick set to avoid having to manage the carbonation for a long period of time as I've no scaffolding on which to hang hessian/plastic.

The bricks are relatively modern, very hard and built using cement mortar so I'm not really concerned about breathability for this smallish area, it's more for cosmetic reasons.

 

[Nemesis]

I've never used the stuff I have to say - wonder if you need to work it more?

The only concern is will it have a similar effect as the cement? It's certainly not as breathable as non-hydraulic.

 

[skier-hughes]

It's a question of working it well and adding water little by little. It sounds to me like you've gone from just too little to just too much in one go.

When I've used it I've had no problem.

Graham

 

[Gervase]

It needs a lot of mixing. If you're using a mixer, once the mix has homogenised, leave it running and go away and have a slow cup of tea - you need to get it to the state where it is plastic enough to spread, but sticky enough to hang on your trowel when you turn it upside down.

 

[Craig]

Sounds just like my porridge.

 

[chuckey]

On the back of St Astier lime bags they say " use a good quality mixer and mix for a minimum of 20 minutes". - Any ideas what a good quality mixer does and a poor one doesn't?. Use a silver plated spoon?
Frank

 

[Nemesis]

A good quality mixer is one who also makes the tea and provides choccie biccies.