lime plaster problem

[noble78]

Hello

As the title suggests I need your advice!

We (my plasterer!) are using an NHL 2.5 2-1 mix of lime and plastering sand but it does not seem to spread very well and plasterer says it seems too sandy to gain a smooth finish. Would a 1.5-1 or even a 1-1 mix be better?
It is internal walls that are lime plastered but we have had to repair some patches that has blown by being repaired with cement over the top! Couldn't make it up! We went back to brick with a lime base coat.
Anyone come across anything similar? How did you resolve it?

Thanks in advance

 

[noj]

For an NHL Finish Coat: 1 part NHL2 1 part Fine Silica Sand is suggested

Or use a premix fat lime - I've used https://www.lime.org.uk/products/li...plastersrenders/lime-top-coat-finish-plaster/ with success. Other brands are obviously available

 

[formerly known as]

Why is everyone using NHL for plaster and render? It is horrible to use and isn't as permeable as a fat lime.

 

[88v8]

Because until you arrived, or returned as the case may be, this has been an NHL forum, or at least we think it has, although whether one is referring to Natural Hydraulic or Non-Hydraulic can sometimes be a tad hard to discern.

No wonder lime fell out of favour.
http://buildinglimesforum.org.uk/about-lime
Lime... a source of confusion.

While cement is pretty much cement. Cement; lime for dummies.

Ivor

 

[MatthewC]

The 2:1 plaster which I bought for my house clearly used a sand which was far finer than plastering sand with those quite large bits in it. However I couldn't say what sort of sand it was.

I agree with using lime putty rather than NHL for plastering or mortaring (if conditions permit) - when I mixed a barrow load of NHL for building a wall, it was going off before I had used it all, so had to revert to doing small mixes which, although tiring, was far more effective.

Matthew

 

[skier-hughes]

Why is everyone using NHL for plaster and render? It is horrible to use and isn't as permeable as a fat lime.

I've been on two lime courses and everyone says they are just as permeable.

 

[noble78]

Thanks all!

It was a non hydraulic mix that just didn't go well at all! Bless my plasterer for trying it (he's become a convert to lime through Google ) I've sourced some fibrelime which is being delivered tomorrow, fingers crossed!

I agree the lime terminology is really confusing which will deter some from using it.

Thanks again and good luck in your projects!

 

[formerly known as]

Why is everyone using NHL for plaster and render? It is horrible to use and isn't as permeable as a fat lime.

I've been on two lime courses and everyone says they are just as permeable.

were they also selling it??

 

[formerly known as]

Thanks all!

It was a non hydraulic mix that just didn't go well at all! Bless my plasterer for trying it (he's become a convert to lime through Google ) I've sourced some fibrelime which is being delivered tomorrow, fingers crossed!

I agree the lime terminology is really confusing which will deter some from using it.

Thanks again and good luck in your projects!

Fibre lime and warm cote appear to be quite similar and both easy to use.

 

[skier-hughes]

One wasn't, it was at Sheffield energy centre, or similar name.
Other was selling NHL, Putty and their own ready mixed, so no reason to say NHL is as permeable as putty as they could sell me whichever.

I've never ended up being able to mix it correctly, I now buy ready mixed, which is great for me.

I also had my lime mortar tested to see how it was made up and the closest they could suggest was NHL3.5, considering the house is 500 years old I took a closest match as ok

 

[formerly known as]

the trouble with mortar analysis is that it doesn't take into account the fact that contamination both in aggregate and lime can show as pozzalanic material which can have an hydraulic nature ....... although clay content in aggregate and ash in lime are far less hydraulic than an hydraulic quicklime.

 

[skier-hughes]

Well they've been analysing lime and other stuff for years and came well recommended, so I think they new what they were doing, if my son wasn't getting married in the paddock in 10 days I'd look up the report and post it for you, it was 2 or 3 pages long (done 10 years ago now!)

 

[Gervase]

I'm not a fan of NHL for plastering, but when I have used it I've noticed big differences in the different makes of lime. Castle brand is probably the worst, while Singleton Birch is the best; a lovely creamy mix which is almost as good as a fat lime plaster.
That said, fat lime plaster is the stuff to use. If you're concerned about curing times and hardness, add a pozzolan to the mix - Metastar is good. Your plasterer will be pleasantly surprised at the ease of working with a 'proper' plaster!