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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorselly
    • CommentTimeJul 22nd 2018
    Is this a crazy idea?

    I've got an old stone barn which either needs repointing or re-rendering. The stones aren't amazing so don't care about keeping them and the foundations are shallow so I don't want cracks in the future. In the future I may convert it so I wan't to keep it breathable but also insulated

    Can I make up my own hemp lime mix using some shiv, some lime and sharp sand?

    What could go wrong - at the end of the day its only a render isn't it?
    • CommentAuthorgyrogear
    • CommentTimeJul 22nd 2018

    read this maybe...


    • CommentAuthortony
    • CommentTimeJul 22nd 2018
    Insufficient insulation. If it is going to crack then it will crack, render will show cracks more and will be more difficult to repair.
    • CommentAuthorselly
    • CommentTimeJul 22nd 2018
    So tony you reckon maybe best to just lime point
    as normal and deal with insulation another way (unless I externally insulate) but thats expensive for a shed I may never use as a dwelling
    • CommentAuthortony
    • CommentTimeJul 23rd 2018
    I have EWI'd my stone buildings, OK as a retrofit to already converted to dwellings. The walls in part were without render and there I put up the EWI by putting a thick bead of adhesive top and bottom of the EPS sheets with 5 blobs on the centre line and then pressed this to the wall, this took care of the unevenness of the walls and avoided the cost of a levelling render and prevented convection between the wall and the EWI. You might find that putting on EWI in this way may not be too much different to the cost of repointing given the time it takes to rake out and repoint which will be expensive in labour. (The EPS was put up DIY and the render coats by professional labour).

    It could depend upon the likelihood of using the building as a dwelling or office or what and perhaps resale value may come into it. If conversion is more than 50% likely then perhaps EWI
    • CommentAuthorselly
    • CommentTimeJul 23rd 2018
    Just been chatting away and I think I'll just use NHL3.5 and sharp sand and do the bagging technique.

    I could use EWI but it would spoil what I have and be a bit pricey at the moment. You never know in 10 years time I want to convert I can always tack on ewi somehow
    • CommentAuthorblacksmith
    • CommentTimeJul 26th 2018
    Very helpful guy - Steve Allin - I'm in mid Wales and when he visited CAT (Centre for Alternative Technology) was intent on coming over to help me with my hemp lime project. I wasn't ready but he was game. Take a look at his site and in the links there are some videos, one dealing with hemp/lime render. I am using hemp shiv horse bedding, sharp sand and hydrated lime currently as infill panels in timber frame work and it works fine, skim of lime plaster after a few days. The whole thing takes a few months to harden off currently and will then continue to. No adverse affects. I did some test panels four years ago to test the methodology and materials - works brilliantly for me. My building regs go back to 2007/8 and have a mixture of insulation - I am a solitary self builder so it's taken me a while to get where I am today.

    Tried the cement mixer method but prefer my own way - I use a large sheet of old DPM and mix on that. I use a builders bucket to measure out quantities of hemp/lime/sand. After turning over to mix with shovel I spread it out to approx 1 1/2 inches and I find it much easier to control and wet down with hose - mixing is something of an art and takes approximately and hour from measuring out to being ready. When the hemp has absorbed enough water (the mix is not sloppy nor dry at this point - just hand balls when compressed) I rub the mix through a mesh box I made up and the resulting mix is wonderful to work. Yes it takes time but then I work on my own and that's the way it is.

    I may be using it (Hemp/Lime) as a plaster but have not commited yet - after seeing the Bauwer Light product on this forum I may give that a go - looks interesting and in all probability easier to work with. Maybe I should try a few bags and see how it works.

    Unless your kitted out with a decent mixer I would imagine hemp/lime plaster is hard work, depends on how much area you want/have to do - I have a mortar mixer for this I got ages ago and may need to mod it slightly. If your in mid Wales or passing through drop me a line and come see for yourself.

    • CommentAuthorSilky
    • CommentTimeJul 28th 2018 edited
    Pointing an old stone building can be quite a daunting time consuming task, couple of ideas here if it is any help. If you might convert later it's worth getting the joints filled properly so that it will help with air-tightness?

    I buy pre-bagged NHL lime render (cheapest ca. 7 Euros for 25kg when in bulk in Germany). I open the bag, drop it into a horizontal mixer, add some water and then go and do something else. 5 minutes later I can point. Because of the grading of the sand this stuff is far superior for pointing, it's sticky, can be pushed and you can deep fill joints etc.. and yes it is also recommended for brick work as well as render. Not sure what you can get in the UK, there are a couple of brands here that seem ok. If you did go the pre-bagged route watchout for people selling 'lime render' that has had a lot of cement added to it, check the classification isn't too hard (PII ?)

    I would recommend to use a small angle grinder with a diamond disc, I know it's a little frowned upon because you will 'damage' the stones slightly, but it is so quick in comparison to any other way I've tried. Use the disc to cut out / rake out the front of the joints, if you have a tight joint cut it a little bigger so you can get a pointing trowel in there (or those long thin ones, can't think of the name, I have 5, 6, 8, 12 mm ). Obviously mask, goggles, hat etc.. and then you can fly through.

    After cutting go over with a compressor to blast everything out (long think attachment is boss for getting into the joints), then wash out with a hose (a hose attachments with different sprays/jet sizes/flow control/lock on/off etc.. are great for this).

    edit : just adding a link https://www.historicenvironment.scot/archives-and-research/publications/publication/?publicationId=b6cb68de-3207-4786-a0d8-a595010402fa
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