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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    Hello all, I hope everyone is well.

    I am at the junction where I need to think about applying my internal plaster. This will be lime based to keep the house as breathable as possible.

    Originally I was keen on attempting this myself. Then after I patched some render I went off the idea as it was not something I enjoyed (under the gable etc.).

    However after recieving plaster quotes in excess of 120 per M2, we actually can't afford a professional lime plasterer as the cost would be half our budget!!

    So I am now full circle again and wondering how easy it is to internal plaster with a lime product? There are many products out there and will need to decide which one. The house is an old cottage but has mostly flat walls (hopefully easier) and I don't mind if these end up a little wavy as you know what the say; it adds character!

    It will be going on a mixture of bare masonry, wood wool board and wood fibre board. Thank you
    • CommentAuthortony
    • CommentTimeJun 4th 2020
     
    Either go on a course, work for a plasterer for a day, preferably doing it with lime.or go for it, skimming is easy watch it on U-tube. It isn’t difficult, wear safety goggles or better a face shield

    Try some skimming first. Use battens to help keep things straight for basecoat work......

    Use lime putty not the stuff in bags
    • CommentAuthorrevor
    • CommentTimeJun 4th 2020
     
    I thought our lime plastering was dear at about £65/£70 sq M I would look for other quotes. Our base coats were sprayed on after dubbing out by hand so made process much quicker although it required lots of visits. Perhaps you are in a location where you cannot get the equipment close up the compressor that was used was big and noisy and had a pan mixer on site also. The materials are reasonably priced it is that you need it a lot more of it than conventional plaster. It is a skilled job I would not attempt it even though I have done a lot of conventional plastering over the years the plaster is a lot more corrosive also than standard stuff.
  2.  
    Do it yourself if you don’t mind a bit of character.
    You will soon get the hang of it. Be confident and prepare to get messy!
    Get it on the wall quick and rough, then go over it all to tidy up.
    I am not a plasterer but have done my own lime plastering (generally quite practical though).
    The hardest type of plastering IMHO is the thin skimming of plasterboard. I have had a go at this too, on small areas, but I would need a lot more practice to feel confident about skimming a plasterboard wall and getting it perfect!
    Lime is very forgiving, lime putty takes ages to go off so you won’t run out of time to get it just how you want it once it is on the wall.
    We did some areas sponged/rubbed off with a damp sponge where it was on stonework, to get a more rustic “hand applied” look.
    We also used up some bagged NHL5 left over from the floor slab to lime plaster flat walls over hempcrete (mixed with sharp sand and soft sand) That went off a lot quicker but was still easy to use.
  3.  
    It is a strange one, you could get machinery right to the door and we are in Norfolk so plenty of people around who do it.

    Perhaps the next quotes will be less...!

    I did see people gunning on a base coat, it looks very good (and quick) though clearing up the mess might be interesting!

    Thanks

    Posted By: revorI thought our lime plastering was dear at about £65/£70 sq M I would look for other quotes. Our base coats were sprayed on after dubbing out by hand so made process much quicker although it required lots of visits. Perhaps you are in a location where you cannot get the equipment close up the compressor that was used was big and noisy and had a pan mixer on site also. The materials are reasonably priced it is that you need it a lot more of it than conventional plaster. It is a skilled job I would not attempt it even though I have done a lot of conventional plastering over the years the plaster is a lot more corrosive also than standard stuff.
  4.  
    Thank you. I feel a bit more confident now...
    Posted By: Dominic CooneyDo it yourself if you don’t mind a bit of character.
    You will soon get the hang of it. Be confident and prepare to get messy!
    Get it on the wall quick and rough, then go over it all to tidy up.
    I am not a plasterer but have done my own lime plastering (generally quite practical though).
    The hardest type of plastering IMHO is the thin skimming of plasterboard. I have had a go at this too, on small areas, but I would need a lot more practice to feel confident about skimming a plasterboard wall and getting it perfect!
    Lime is very forgiving, lime putty takes ages to go off so you won’t run out of time to get it just how you want it once it is on the wall.
    We did some areas sponged/rubbed off with a damp sponge where it was on stonework, to get a more rustic “hand applied” look.
    We also used up some bagged NHL5 left over from the floor slab to lime plaster flat walls over hempcrete (mixed with sharp sand and soft sand) That went off a lot quicker but was still easy to use.


    Thanks Tony

    Posted By: tonyEither go on a course, work for a plasterer for a day, preferably doing it with lime.or go for it, skimming is easy watch it on U-tube. It isn’t difficult, wear safety goggles or better a face shield

    Try some skimming first. Use battens to help keep things straight for basecoat work......

    Use lime putty not the stuff in bags
    • CommentAuthorKenny_M
    • CommentTimeJun 4th 2020
     
    Due to lockdown and not being able to get anyone, I have been doing a bit of plastering for the first time. I swore I would never do this as I was always rubbish trying to patch any more than a small area, but I got the hang of it and was improving quickly - until the multi-finish ran out and I couldn't get any more! The one wall that I got finished is looking good, and should be fine for painting after one or two fills here and there.

    Lime will be a bit different but I would imaging the technique will be similar, and when I have used lime outside I have found it easier because of the time it takes to dry. There is so much on youtube and I think its worth watching a number of different videos to pick up different tricks. There are videos on there about lime plastering specifically. Lots of tips and tricks on there for non plasterers too, like battening out to do vertical sections in order to get square and flat, then removing the battons and filling that point like jointing on plasterboard.

    Also look up Darby and Speedskim in screwfix. I didn't get these but think they could help.
    • CommentAuthorowlman
    • CommentTimeJun 4th 2020
     
    A Darby is essential IMO, different lengths are available.
    Many so called professionals choose not to use them to their own discredit IMO. I do lots of contemporary interiors which demand precision finishes and I don't care how good the plasterer you can rarely get it with a trowel and hawk alone.
    A crap finish usually manifests itself when the decorator comes and tries to line up wallpaper, corners bent like bananas and with waves on the surface so any patterns are impossible to deal with.
    When the client decide they want wallpaper at £80+ a roll mistakes become expensive.
    If you go it alone, make sure your corner beads and trims are spot on plumb, and level. Removable, planed, straight, timber battening, also plumb, as others have said, I think is best for beginners.
    •  
      CommentAuthordjh
    • CommentTimeJun 4th 2020 edited
     
    There's a good article at https://www.buildingconservation.com/articles/internallimeplast/lime_plaster.htm

    My lime plasterer used a bagged product for the top coat internally though it's also available as a putty - I think it was Regency Lime Plaster e.g. https://www.mikewye.co.uk/product/regency-lime-plaster/

    edit: I've checked and I'm wrong - he used tubs of the product, not bags. I don't know whether bags are available.
  5.  
    Posted By: rosecottageafter I patched some render I went off the idea


    I think sometimes patching in is harder than doing a complete layer because the join is often noticeable.
  6.  
    Thank you for all the comments. For myself a second hand Darby and all the other bits when I was rendering so seems silly to at least not have a go (he says).

    All of the reputable firms around here I have spoke to no longer use a sand mix due to weight, so I am looking at a couple of different insulating lime plasterers to give a little bit more warmth.

    I will probably just do my inner external walls and some brick internally but have all the stud work skimmed in a one coat plaster to get a similar colour and texture (at lower costs and quicker). Thanks
    • CommentAuthorCWatters
    • CommentTimeJun 5th 2020
     
    I would try and find a course or try a small area first. I'm pretty handy (electrics, brickwork, woodwork no problem) but find with plastering is difficult to get the quality I want.
    • CommentAuthorJonti
    • CommentTimeJun 5th 2020
     
    I did my own plastering with no previous experience. The first part was very easy as I went for a rustic uneven look. Make sure you get the keying of the surfaces right and sealing the plaster afterwards. Mine has been on 10 years now and still looks great.

    As previously mentioned. Thin layers on plasterboard is really difficult and needs much more practice. Also, it is a really messy job.
    • CommentAuthordb8000
    • CommentTimeJun 6th 2020
     
    After a really poor experience with professionals, I thought I’d give it a go myself.
    I went on a two day residential course at Ty Mawr near Brecon.
    It was fun and I’ve done my own since. I’d struggle with more than a couple of walls at a time thought because of the physical demands! I’ve not had too much to do in my house thankfully.
    They also sell bagged (wet) pre-mix for the top coat which works excellently.
  7.  
    Posted By: db8000They also sell bagged (wet) pre-mix for the top coat which works excellently.


    This might be the way to go if you’re not sure exactly what mix to do, and if you are doing it on your own you won’t have to wait while you put another mix on.
    +1 on the physical work, I would do one wall first and then see how you feel the next day. You might find that you are using the same muscle group repeatedly and need a change of task between plastering.
  8.  
    Go on a course for lime plastering. If you're reasonably practical, you will pick it up.

    You need to know how to mix it. I used to mix it too dry, which is physically hard. Then I saw a sprayed render that was so wet it only just stayed on the wall. But much easier to get on quickly and to level up.

    You also need to know how to take care of it afterwards.
    • CommentAuthorrevor
    • CommentTimeJun 12th 2020
     
    I have mixed lime NHL 3.5 think it was to render stone wall level and between battens to form a level surface behind EWI. I found it difficult to mix with the sand in a concrete mixer and found best way is to slurry the lime with water in a bucket with a paddle mixer. Put this in the mixer then gradually add the sand. Takes a good 20 to 30 mins to mix. Rendering was good enough for what I was doing but would not have tackled interior walls though.
  9.  
    Thank you all. Still a bit undecided but think I am going to attempt it myself...
  10.  
    On wood-fibre board, quite easy. Wood-wool board I have never used, but same rule should apply. On W-F, first apply a c6mm toothed (tiling trowel) coat. Very, very lightly 'float' glass-fibre reinforcing mesh 'on the surface' of this layer. Do not push it in - just enough to adhere. If you push it right back then it isn't reinforcing the layer it's meant to reinforce.

    When this layer has stiffened *very slightly* (you should not have to wait too long - though lime is a very inexact science!) do a 'wet-on-wet coat' (trowel *very* lightly!) until you have largely 'lost the mesh'. You still have another coat (at least) to go once the wet-on-wet is dry, so if there is a little 'mesh-ghosting' still, you'll lose it in that next coat.

    For some that could be the last coat. I use Baumit plasters - RK70 for the base coats (and the (toothed) adhesive layer for the W-F boards) and sometimes use their 'Glatt' finish.

    That's a slightly odd one if you are used to gypsum - it's a bit like thin cheese sauce (but does not taste as nice), and does not really 'build', so get the base-coat really smooth *before* you do the Glatt. Wait until the base-coat is really stiff but not 'gone off' (probably about 4 a.m. according to the Law of the Sod) and rub over with a moist sponge. It's a bit like moving custard through the skin - you will get rid of minor imperfections and even slight 'valleys' - and then you are ready for the 'Glatt'. Note if you do use the 'Glatt' don't be too hasty. Allow the base coat to dry for at least 2 days in warm weather and 4+ in moister weather.

    Where you are plastering onto existing surfaces, if they are not too flat, build up screeds - vertical lines of plaster, plumbed to your satisfaction - let them go off and then plaster between them.

    You probably already know all the precautions re respiration, skin and eyes.

    Have fun!
  11.  
    Posted By: Nick ParsonsOn wood-fibre board, quite easy. Wood-wool board I have never used, but same rule should apply. On W-F, first apply a c6mm toothed (tiling trowel) coat. Very, very lightly 'float' glass-fibre reinforcing mesh 'on the surface' of this layer. Do not push it in - just enough to adhere. If you push it right back then it isn't reinforcing the layer it's meant to reinforce.

    When this layer has stiffened *very slightly* (you should not have to wait too long - though lime is a very inexact science!) do a 'wet-on-wet coat' (trowel *very* lightly!) until you have largely 'lost the mesh'. You still have another coat (at least) to go once the wet-on-wet is dry, so if there is a little 'mesh-ghosting' still, you'll lose it in that next coat.

    For some that could be the last coat. I use Baumit plasters - RK70 for the base coats (and the (toothed) adhesive layer for the W-F boards) and sometimes use their 'Glatt' finish.

    That's a slightly odd one if you are used to gypsum - it's a bit like thin cheese sauce (but does not taste as nice), and does not really 'build', so get the base-coat really smooth *before* you do the Glatt. Wait until the base-coat is really stiff but not 'gone off' (probably about 4 a.m. according to the Law of the Sod) and rub over with a moist sponge. It's a bit like moving custard through the skin - you will get rid of minor imperfections and even slight 'valleys' - and then you are ready for the 'Glatt'. Note if you do use the 'Glatt' don't be too hasty. Allow the base coat to dry for at least 2 days in warm weather and 4+ in moister weather.

    Where you are plastering onto existing surfaces, if they are not too flat, build up screeds - vertical lines of plaster, plumbed to your satisfaction - let them go off and then plaster between them.

    You probably already know all the precautions re respiration, skin and eyes.

    Have fun!


    Thank you Nick!
    •  
      CommentAuthordjh
    • CommentTime3 days ago edited
     
    Posted By: Nick ParsonsOn wood-fibre board, quite easy. Wood-wool board I have never used, but same rule should apply.

    Wood wool boards are a lot rougher than woodfibre. There are gaps you can see through, let alone blow through. So it provides a much better keying surface for plaster. We put wood wool boards over the woodfibre insulation overlapping the window reveals for that reason (we had wood wool boards elsewhere covering timber and timber framing to provide a good key). The scratch coat is just pushed into the wood wool, no need for toothed trowels and suchlike, they'd just get caught.
  12.  
    Thanks for filling in my knowledge gaps, djh!

    When I first saw 'smooth' wood-fibre I thought 'there's not a chance render or plaster will stay on that. There's no key!' - and I was wrong. It stays on very well indeed, but I agree wood-wool has an inherent and presumably excellent key.
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