This is a short post showing videos and photos of the Diathonite being applied. It was a busy three days. BorderLime worked really hard and did a superb job. We worked alongside them, with Tom on the mixing machine. You can see from the videos the speed at which the product goes on to the walls, and the mess it creates. It really was worth masking stuff up thoroughly, although we still spent several weeks vacuuming fragments of cork and lime dust.

The finished result was transformational. We’re yet to experience a winter with it, but I’ll post an update when we have some more feedback on its performance.

Videos of Diathonite Application

Diathonite Mixing Machine in action

This video shows the diathonite mixing machine in action. A bag of Diathonite Thermactive is placed onto the top of the hopper. The serrated edge cuts the bag open. The top and bottom of the bag are lifted up to pour the dry mixture out. It filters down through the grille into the hopper where it is dosed with the correct amount of water, and mixed up. It is then pumped into the building through the hose and sprayed onto the wall.

Spatter coat application onto smooth substrate

This video shows the first “spatter” coat of Diathonite Evolution being applied to a bare brick internal wall. The hose brings the Diathonite into the building from the machine which is mixing it up outside.
The spatter coat serves as a “key” for the proper base coat to adhere to – this is important if the substrate is not very grippy, as was the case with these smooth bricks. It was left to dry for a short while prior to the base coat being sprayed on at a thickness of up to 20mm.

Spraying the second coat onto the stone walls

These two videos show the application of the second coat of Diathonite Thermactive, the day after the base coat was applied in the same way, and roughly trowelled off. The Diathonite goes on in a continuously sprayed “worm”, which is then trowelled by hand to make a uniform finish. This coat will be left to dry for a couple of weeks prior to hand finishing with a lime plaster.

Trowelling off the second coat

This video shows the Diathonite being smoothed off after the second coat has been sprayed on. It is trowelled by hand to achieve a finish which is ready for a final coat of lime plaster.

Photos of Diathonite Application

To read about how we decided to use Diathonite and how we prepared for the installation, read the other posts.

7 comments to “Diathonite Insulating Lime Plaster – Part 3, Installation”

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  1. Karl Roscoe - 30th August, 2019 Reply

    Great stuff, thank you once again for sharing.

    In the picture ‘Finished top coat and the join into stone wall…’, regarding spray the ‘left’ wall, is the ‘left’ wall partly external or completely internal? I’ve been thinking about spray diathonite three inches into a room on the internal wall that meets an external wall? Your left wall looks like at least a couple of feet and so interested to know the reasoning there.

    Where did you apply the Deumix? In for the first foot up a wall where rising damp was an issue, then continue with Thermactive or Evolution?



  2. LoisLogsLune - 17th September, 2019 Reply

    Hi Karl,
    Thanks for your question. The wall in that picture is in fact the external gable wall. In a yet-to-be-published post, I will explain the detailing of the gable, but in summary the gable had a new stone wall built on the outside of it, and a fully filled cavity using Dritherm. So whilst this wall is now insulated, there is the thermal bridge between the “external” insulation in the gable, and the internal diathonite (see the detail in the sketch
    We returned the diathonite approximately 1m along the gable wall. I suspect that 3 inches won’t really provide much benefit, but our 1m corresponds to the purlin above, so was a natural place to take it to.

    The Deumix was applied to two areas for the first 1m height on the external back wall of the property which is actually below ground level outside (albeit with external insulation, tanking and suitable drainage). Whilst these were not specifically “problem areas”, both were in corners under the stairs, and so had limited air flow. The carpets which were there were mouldy and smelled bad, and there was a general sense of dampness. Whether this was rising damp or just stagnant air in a cold corner is difficult to say, but we took the opportunity to apply the Deumix whilst doing the rest of the work.

    When we returned from a recent trip away, for the first time since we’ve owned this place, it didn’t smell musty when we returned, so I reckon the Diathonite is offering a benefit already.

    Hope this answers your questions.
    Best wishes,

  3. Plastering Auckland - 8th May, 2020 Reply

    This is a short post showing videos and photos of the Diathonite being applied. It states about diathonite insulating thermactive lime plaster application and installation . Thanks for this amazing article. Great blog indeed, will visit again future to read more!! You must also check out it has some great insights too.

  4. Geoff Bolam - 13th May, 2020 Reply

    Hi Lois, Thanks for posting the article.
    I’m considering Diathonite for the conversion of a small church to a holiday let.
    We have similar problems of damp in the walls – caused by a modern concrete floor and damp-proof membrane, cement pointing, leaky gutting, no heating, etc.
    We were initially advised to dryline the entire building but this rejected on conservation grounds, and then to just remove the cement pointing and repoint and repair with lime.
    However, we’re going to have to work hard to heat the building as the roof cannot be insulated much either, so now looking at insulated plaster at it appears to offer a solution both issues.
    I’ve been looking at Diathonite but our architect is cautious about using a ‘modern’ material in a historic and about the longevity of it.
    I just wondered if you’d experienced any issues, such as cracking, performance, decorating etc, since having it installed?
    Thanks Geoff

    • LoisLogsLune - 13th May, 2020 Reply

      Hi Geoff,
      Thanks for your post. I think you’re doing the right thing in avoiding drylining – when we removed ours it was horribly mouldy behind, which can cause really bad indoor air quality, and aggravate conditions like asthma. Lime pointing will help too – it allows the stone to dry out quickly and won’t trap moisture.
      The Diathonite seems great for us so far – it’s been in for 12 months now. I think I’d struggle to describe Diathonite as “modern” – its main ingredients being lime (an ancient product!) and natural cork – you only need look to some of our historic buildings to find lime stands the test of time much better then cement. In terms of performance, we’ve not observed any cracking or damage beyond one or two spots of superficial cracking on our lime plaster top coat where it dried too fast, but we have no reason to suppose this goes into the diathonite layer, and we will remedy these when we get to decorating those areas. But there is no damage around, for example, the front door, which does vibrate a bit as it opens and closes – the diathonite is solid there. There is one area of diathonite which may need to be addressed – a small wall, around 1x1m seems to have lifted; we think this is because it was applied to smooth brick in that spot, and because access was especially awkward just there, we don’t think it got its spatter coat key. Elsewhere though it seems really solid.
      We used a lime and sand mix for the finishing plaster coat. There was some staining as we applied this, a darkish yellow/brown stain leaked through, and we think this was tannins from the cork, however it has faded back to the lovely soft warm grey of the lime plaster coat without any need for intervention. We’ve been advised that we should use breathable paint (avoid vinyl etc), and to keep the area of tiled finish to a minimum to ensure it performs as intended (I guess to manage any moisture loading from the outside). I think also we’ll have to put up a framed area to install the shower cubicle against the diathonite wall, but these sort of considerations are normal for managing an old building.
      To be honest, i really would struggle to fault it as a product. It was expensive as a material, but the installation cost was lower than for some other approaches because it was so fast for the installers to do the whole job. I’ll try and get some pictures posted up of the finished bits asap.
      Your project looks really exciting – good luck with it!

  5. Colin - 9th July, 2020 Reply

    Hi Lois,

    A great three posts on your application of Diathonite. Down here in Kent, we are about to embark on a retrofit of a Victorian house with solid brick walls – so similar enough to learn from your experiences, but also different enough that I can’t just apply them 1:1.

    My question though is related to drying time – specifically, how long did it take your 50mm application to dry? I can see from Diasen’s tech specs that they claim 15 day’s drying time, but I can’t see what thickness that relates to. The question we are asking ourselves is – how long do we have to wait from application (60mm Diathonite + Argacem HP) coat before we can paint the walls?

    Any insight you can share will be very welcome. Thanks,

    • LoisLogsLune - 12th August, 2020 Reply

      Hi Colin,
      Thanks for your great feedback.
      In relation to your question, my understanding is that the 15 days before the finish coat and then perhaps the same again before painting, providing that you are using a breathable paint. The products may continue to cure after this time, but assuming the condition is not too cold and that there is reasonable ventilation to avoid high humidity, it can continue to cure after the top coat and painting. A breathable paint is important not only to allow the product to finish curing properly, but to ensure that it can function as intended throughout it’s life – it will manage the moisture content of the walls by absorbing and releasing moisture according to the conditions, but only if there is no coating blocking this process.
      My own experience is probably irrelevant – since we’ve not yet painted any of the walls! We will leave most of them the natural colour. We also used a lime plaster top coat (lime and sand mix) instead of argacem on the basis of cost – I am preparing a post on this topic for publication later this year (when I have the time). The top coat was applied about 3 months after the diathonite, because we were doing other jobs in the meantime.
      Hope this helps!

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