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Using lime for outbuilding foundation

 
Helen
(@helen)
Member

Hello, and apologies that this topic is relating to foundations for a whole new build rather than an extension - I couldn't find an exact category! I'm building a low brick wall in the garden as a greenhouse base and after spending so long removing concrete and cement from the house & garden and replacing with lime mortars, I'm keen to avoid using concrete foundations (I know they don't need to be deep, but still...). I'm struggling to find any info online about using lime/limecrete for foundations, although have laid limecrete slabs inside the house. Does anyone know if it's possible to do this? I have lots of mature lime putty leftover from repointing which I could use. Many thanks in advance 🙂

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Topic starter Posted : 16/02/2022 4:02 pm
Chris Brookman
(@chris)
Member Admin

Hi Helen

Others may have different ideas but in my previous role I used lots of lime mortars for building stone walling and we simply added pozzolans, such as Metastar or GGBS to the lime mortars to make them set below ground. Do you have any masonry that you could lay in the mortar? I'm not sure how well using lime putty with graded aggregate (to produce a lime concrete) will work, purely from a time taken to set perspective. I'd suggest the pozzolan is a must though. Hope that helps.

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Posted : 17/02/2022 3:57 pm
Helen
(@helen)
Member

Hi Chris,

Thank you for this advice - I really appreciate it 🙂 I have a full bag of Argical bought for a previous project and not needed, so do have pozzolan at the ready! However, based on your thoughts re time to set (in such a damp setting with only the top surface of the foundations open to the air) do you think I'd be better to save my lime putty and go for NHL instead, and then not use the pozzolan, but add some masonry as you suggest? 

ReplyQuote
Topic starter Posted : 17/02/2022 4:24 pm
Chris Brookman
(@chris)
Member Admin

Hi Helen

I think the NHL would be a better choice to produce a mortar/concrete in the footings. I would use some NHL5 if you have it available so that you create a robust, load-bearing footing. I personally would use the lime putty you have for internal finishes (if you need it on the wall) or for laying the bricks. This would allow the bricks to be recycled at some point in the future, if required.

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Posted : 17/02/2022 5:38 pm
Helen
(@helen)
Member

I think that's the way I'll go then Chris, I know where I can get some NHL5. Agreed about the putty and funnily enough have been knocking the old mortar off some lovely handmade bricks this week for building the wall, and the lime mortar crumbles off so nicely - then you can see where more recently someone has used cement on some of them and there's no shifting it. Such a shame. Thank you very much again.

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Topic starter Posted : 17/02/2022 6:34 pm
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