Hemp Lime - Any advice?

[MissSteel]

Hi Guys,
First time poster! I have just discovered this website and have already spent many hours reading through the forum :shock: My fiance and I have just started our renovation experiance. He inherited a period property about a year ago and we have decided to make it into our home. Unfortunatly the house is in fairly bad repair, we have to re-roof it and replace all the windows. There was a heavy layer of cement render in the front and one gable end of the hosue which we have removed and we are going to re render with Lime plaster.
This is were my first question comes in! We are interested in a company that supplies Hemp Lime products, both for insulating and rendering the house. Their mix for external rendering sounds very good, the supplier as explained that he uses fat lime not hydraulic lime like most suppliers. This he says leaves it easier to work with as any fine cracks ...etc can be closed while the render is curing. I'm not sure about the whole thing, as i have no experiance of this watsoever. We would like to have a coloured lime dash finish on our house as i am not overly fond of the grey look, our plasterer has said this will be difficult to acchieve as it has to be mixed in batches and it is hard to get the colour consistant over the whole building. But with the Hemp Lime, because we would be ordering a good quantity, and it is mixed by the supplier then they can colour it and there would be no issue.
Sorry for my rambling! Basically i am wondering if anyone has any experience of using hemp lime plasters and if they as good over even better then the normal hydraulic lime render.
Thanks!
MissSteel.

 

[Zebra]

Hello and welcome to the forum. I've used lime hemp plasters internally but don't have experience of using it externally. I have heard of hempcrete, which is a lime and hemp mix which you pour into shuttering around a timber frame. I don't know if this would be of any use to you. What's your house constructed of?
I have a new fat lime external render on part of the house, though not with hemp, and it's very breathable and good, though not very strong. I also have a through-coloured render on part of my house, which is part of a system supplied with the external wall insulation boards which I used. I do like the idea of not ever having to paint the house.
I can understand it would be difficult to mix your own colour on site but it's not only the lime hemp that you can get with the colour already in it. There are other types of ready mixed powder that you can get which are not hemp based. I can give you the supplier I used if it helps.
Hydraulic lime is the right stuff for some uses, fat lime is the right stuff for other uses, it depends what it is you're working with and what the wall construction is.
Not sure what advice I can give really, besides I've only experience of the one project. I did a lot of research and talked to a lot of suppliers before deciding on my solution, and even then the plan changed as I went along. Good luck though.

 

[MissSteel]

Hi Zebra, Thanks for the reply. The house is constructed with rubble stone ~2-3 feet thick, we were looking into using the hemp lime mix that you described for insulating the external walls. Setting up battens and tamping the mix down between them then plastering over this. We have been looking into breathable insulting methods and this seems like the best option for us. I'm just not sure about using the hemp/lime mix for plastering outside as i am a little afraid as to how the Hemp will act when it is subjected to the elements. I am based in Ireland, so there is only 2 suppliers of Hydraulic Lime and one of hemp lime as far as I know. The hemp mix is about twice the price of the hydraulic lime, so I dont know if it is worth it just to have a nice uniform colour... decisions decisions!

 

[MatthewC]

Hi there - welcome on board.

I've not used hemp at all, nor have I rendered externally, but I have used limewash. Why not just limewash your grey render? It's easy to apply and is not very expensive, even if you have to buy it in England or Wales.

You also say that you have to "replace all the windows". If you have got old, thin wavy glass, treasure it. Don't let a contractor break them all - it really does look good and it's really very hard to get hold of.

And congratulations on making me laugh with your second post:

We have been looking into breathable insulting methods

I've also got a keyboard that often misses out letters but I can't remember a good example which isn't very rude...

Oh, I almost forgot: photos please!

Matthew

 

[Roger H]

Why not just limewash your grey render?

Matthew - My reading is that MissSteel is looking to remove failing concrete render and that the hemp/lime replacement render will be external insulation.

 

[MissSteel]

Hi Matthew C! Haha, thanks for pointing that out! I am the worlds worst at typing/spelling! Thanks for the reply but Rodger H is right, we have removed the cement render from the house and are looking into the appropriate render to replace it with. I know the limewash is a good option, but I really dont relish the thoughts of re-painting the house again and again so if there was an alternative option i would be delighted.
Unfortunatly the house is in very bad nick. It had slates/downpipes and windows missing for many years and there is serious damage to internal woodwork. Also the windows which are cheap replacements from about 50 years ago are in a terrible state, the local CO has been out and has no issues with them being replaced. Also the house was vandalised about 2 years ago, and all the copper was robbed from the house which resulted in all the windows being broken and flooding damage. So all in all we dont really have much original features but a stone house in a lovely setting! I will post some photos soon, just have to figure out how!

 

[Zebra]

We have been looking into breathable insulting methods and this seems like the best option for us. I'm just not sure about using the hemp/lime mix for plastering outside as i am a little afraid as to how the Hemp will act when it is subjected to the elements.

I'm not sure about lime hemp outdoors. Would it then have a top coat of something else? Or would the hemp be the top layer? Hemp, being an organic material, doesn't want to be in persistently damp situations, or it will rot. Having said that, timber can survive externally because it has a chance to dry again after rain, and so, I suppose, would hemp, although whether you would risk it in Ireland I don't know......
As to hydraulic lime, there are different types. You probably know this already from your research, but there is NHL2, which is a weak mix and more breathable, NHL3.5, which is stronger and less breathable, and NHL5, which is stronger still and even less breathable. It's like a sliding scale, where what you gain in strength and speed-of-set you lose in breathability, all the way from fat lime on one end of the scale, to cement on the other end. What type of NHL might be suitable for your house might depend on how porous your stone is, but I imagine that there would be an NHL which would be suitable.
Where I have very soft porous old bricks I have an external render of fat lime only. This part of the house won't be suitable to cover in a through-coloured top coat and will have to be painted with an external clay paint, because the through-coloured top coat is too strong to sit on top of a weak fat lime base coat. You wouldn't put a strong mix over a weak mix.
Where I have modern blockwork however, I could use either NHL3.5 or a part lime-part cement mix as a base coat, with the through coloured top coat. It all depends on the substrate.
As to whether you could get a through-coloured non-hemp-based top coat render for your house, I obviously don't know about suppliers in Ireland, but I used WP Finish by a company called Lime Green in Shropshire.

 

[MatthewC]

Why not just limewash your grey render?

Matthew - My reading is that MissSteel is looking to remove failing concrete render and that the hemp/lime replacement render will be external insulation.

Sorry, I meant to suggest that the new grey render of lime should be limewashed, not the existing concrete stuff.