Lime Render / Plaster

[Adam F]

I've tried not so ask here, and do my own research but I'm struggling to understand the various different terms and products from what Ive read online..... hydraulic, slaked, NHL2 etc, etc....

I have a basic rubble and stone interior wall (ajoined outhouse used as a summer room) which needs re-plastering - I'm looking to replace the rough finish that still exists in places - which barely coveres the material behind and gives a tidy look, but still shows the bumps of the cobble.

I've plastered / rendered with modern materials a fair bit, so I'm happy with that, but I'm really struggling to know what mix of lime I need to use?

Can anyone give me an easy answer? Is there an easy answer!

Many thanks.
EDIT: After more research would I be OK using http://www.heidelbergcement.com/uk/en/hanson/products/cements/packed_products/limes_and_lime_mortars_conservation_range.htm
Mixed 1;3 with sharp sand as a basic render?

 

[Schoolmarm]

You don't really need hydraulic on an internal wall.

That rough finish sounds like harling where it is thrown hard at the wall using a shovel shaped tool.

Gervase is your man with the info as I expect he will do quite a lot of harling.

 

[MdB]

Slaked lime - Heated limestone - highly reactive and fairly dangerous. Not what you want.

Hydrated lime - Made from slaked lime (by adding water). Available as a powder from builder merchants and the like. Goes off in the bag if left a long time or if it gets damp. The cheap way of buying lime and is what a lot of people use. Will not set whilst wet. If you have spare you want to keep, turn it into putty by adding water.

Lime Putty - Made from hydrated lime (by adding water) or directly from Slaked lime (by adding water). More expensive to buy from specialist lime companies. You can make your own from hydrate. Will not set whilst wet and will keep indefinitely in a sealed container.

Hydraulic Lime - Hydrated lime that has additional minerals in it which cause it to set whilst wet. NHL = Naturally Hydraulic Lime where the original limestone contains these minerals. The more minerals, the stronger the set and the higher the NHL number.

For all indoor jobs use Hydrate or Putty - there is no difference between them. For outside jobs, hydraulic lime can be used for either continuously damp conditions or for highly weather exposed positions but hydrate / putty is still best for most jobs.

Strongly recommend going on a day Lime course to learn the differences between lime and modern materials.

 

[christianb]

MdB has it pretty much nailed there.

Ideally you should use only lime putty for interior plastering, but you can also use NHL2 (the softest of them all) if needs be. Or a mix of both. The numbers, by the way, relate to the respective compressive strengths of the lime - NHL5, for example, is the eminently hydraulic stuff they used to use on the foundations of tower bridge. It's like cement.

C.

 

[Adam F]

BRILLIANT!! Thanks all - that is exactly the info I was after. I had a very detailed reply from Gervase too which was superb.

Thanks again!