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    • CommentAuthorLehobbit
    • CommentTimeSep 25th 2020 edited
     
    Hello all. I am a newbie in this group and this is my first post. Myself and my partner Jacqueline have been living in France since 2014. Our first renovation here was in the Charente Department. We managed to renovate an old wreck of a longere and sell on for a decent profit, although that was not our original plan.

    We missed living in a green and hilly/mountainous landscape (in the UK we had lived in Snowdonia/Mid Wales/Scottish Highlands) and so decided to head to the green and lush Plateau Millevaches in the old region of Limousin. The area is a high plateau of forested hills and heather moorland with the highest part being Mont Bessou in Haute Correze at an altitude of 979 metres. There are lots of lakes here and natural sources and the landscape is reminiscent of parts of Mid Wales and the Cairgorms although much more wooded.

    We have just purchased an old granite house to completely renovate and we wish to do as much of it as possible in a eco manner. It comes with four hectares of woodland and meadow and we plan to have mainly wood heating. The house sits at an altitude of 810 metres or 2657 feet in old money. Winters can be cold here (-25 not unheard of) and in our commune there is actually a cross country Nordic skiing station! However recent summers have been crazy hot (40 degrees plus) and with increasingly mild and wet winters.

    Back to the property. It has electric and mains water, however it is desperately in need of a sympathetic renovation. The house faces south and is partly built into the hillside. It's very sheltered from the north with a wooded hillside behind and woodland to the west with other sheltering trees to the east. I have attached a photo from Google earth to show the property in it's setting.

    The roof is going to be replaced and we also plan masses of isolation in the roof and floor. For the walls which are 500mm thick granite stone we are planning to render on the inside with hemp lime to a thickness of about 80mm, possibly thicker if we shutter it.. Also we will be wood cladding some parts of the exterior with external insulation in addition. Internal walls will be created with shuttering and hemp lime.

    What I really wanted advice on was hemp lime suitability for our project. I have the excellent book on hemp lime construction, the "Hempcrete Book", but there is not too much in there on renovation and retrofit. We have located a local source of hemp and chanvre chaux as the French call it is very popular in France.

    What I want to know is about using hemp on the ground floor rear wall of the house. This wall is below ground level at the back of the house. It currently has a few damp issues but the stone wall is pointed/rendered with cement (inside and out) so cannot breathe. Also the 13 metre long roof has no guttering so all that rain is concentrated at the rear of the house which is a flat terrace. We will have new guttering and rainwater management (into the well/storage) plus removing the cement and using lime will let the building breathe again. We talked to a French eco company about using Isohemp blocks to build an new internal rear wall on the ground floor and to leave a small air gap of 10cm as is conventional wisdom between that and the existing stone wall/bedrock. However the French compaany have advised to infill behind the block wall with loose fill hemp lime to bond the block wall to the existing subterranean stone wall? I have since read that hemp lime should not be employed in below ground situations? What are people's thought on this?

    Only the rear wall is below ground level? Also we have an adjoining stable of 28m2 that we want to convert to a living space. Currently it has an earth floor and again it's rear wall is below external ground level. Here we wanted to create a hemp lime insulated floor slab over a gravel substrate. Will this be possible?

    Although it can be wet here in winter the climate is very different to that of much of upland UK. it dries out considerably in summer with the heat and the last three we have seen significant droughts. I have also read that hemp lime can withstand a certain level of damp? So my question is can we use it for our project in all the areas I have discussed. I hope there are some hemp lime experts that can help? Kind regards Paul and Jackie, Correze, Massif Central, France.
    • CommentAuthorEd Davies
    • CommentTimeSep 25th 2020
     
    Hello Lehobbit, welcome.

    Sorry, I'll leave talking about lime to others but my first thought would be to ask how well drained the ground immediately to the north of the house is and whether it'd be appropriate to improve that if there are existing signs of damp. It sounds like there's plenty of space to drain to to the south of the house.
  1.  
    Posted By: LehobbitWe talked to a French eco company about using Isohemp blocks to build an new internal rear wall on the ground floor and to leave a small air gap of 10cm as is conventional wisdom between that and the existing stone wall/bedrock. However the French compaany have advised to infill behind the block wall with loose fill hemp lime to bond the block wall to the existing subterranean stone wall? I have since read that hemp lime should not be employed in below ground situations? What are people's thought on this?

    In a similar situation - basalt stone wall built into a hill (sandy soil) being the rear wall of the house - I built a conventional brick wall, single skin, in front of the stone wall having put a vertical DPC (sheet of plastic) between the stone wall and the brick wall. The gap between the 2 walls in minimum and there is no connection between the 2 walls. This was all done 25 years ago and there have been no problems since.

    In more recent times I have put EWI (standard EPS with thin film acrylic render) on to basalt/rubble infill walls with no problems and a much improved internal thermal performance.

    I have no experience with lime other than using it as the plasticiser for cement mortar and render.

    Your property sounds well located in terms climate protection and the 50cm stone walls should give a comfortable, stable internal temperature - With our house in a similar location we find that in the winter we venture out - think 'Oh - not to bad' - walk down to the road and half way down (by then exposed to the north) we turn around to go back for another jumper! Location with regard to the environment and compass makes a bigger difference than I ever appreciated before living here.
    •  
      CommentAuthordjh
    • CommentTimeSep 26th 2020
     
    The photo didn't appear. It was perhaps too large and you'll need to resize it before posting it.
  2.  
    Welcome!

    I know someone who completely transformed a slate cottage with shuttered hemp/lime. It was not even that thick; the U value is probably not exciting, but the 'moisture management ability' has massively improved the 'live-ability'.
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Posted By: Nick ParsonsWelcome!

    I know someone who completely transformed a slate cottage with shuttered hemp/lime. It was not even that thick; the U value is probably not exciting, but the 'moisture management ability' has massively improved the 'live-ability'.


    Hi Nick. Yes this is what we are aiming for. Apparently hemp lime has a performance that is greater than the sum of it's parts. Great acoustically, seals the walls from draughts. U values alone cannot account for the qualities of the material. We are using the Hempcrete book as a guide, written by Alex Sparrow and William Stanwix.
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Posted By: djhThe photo didn't appear. It was perhaps too large and you'll need to resize it before posting it.


    Hi there. I did try and upload the photo but keep getting an error message? Any idea how I do it?
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Posted By: Ed DaviesHello Lehobbit, welcome.

    Sorry, I'll leave talking about lime to others but my first thought would be to ask how well drained the ground immediately to the north of the house is and whether it'd be appropriate to improve that if there are existing signs of damp. It sounds like there's plenty of space to drain to to the south of the house.


    Hi Ed. Well at the moment the rainwater is concentrated by the roof at the rear and at the front. (no gutters). We will have a new roof in Bac Acier Sandwich panel. This is basically a galvanised steel roof with two skins and 120mm of PIR foam insulation in between. It's a large roof of 156m2 so slate was not affordable (we were quoted €24,000!!) We like the contrast of modern with the old granite stonework. I think the general surrounding land is pretty well drained as the soils here are sandy. Also at the back of the house is a large flat terraced area about 10-15 metres deep and the width of the house (13 metres), beyond that is a 2 metre high stone built retaining wall and then the wooded hillside. We plan to excavate a channel about a metre deep along the back of the rear house wall and put a honeycombed plastic moisture barrier against the back wall and then re fill the void with gravel and drainage pipes. I think once we have done all this as well as removing the non breathable cement render and pointing that the situation will be resolved.
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Posted By: Peter_in_Hungary
    Posted By: LehobbitWe talked to a French eco company about using Isohemp blocks to build an new internal rear wall on the ground floor and to leave a small air gap of 10cm as is conventional wisdom between that and the existing stone wall/bedrock. However the French compaany have advised to infill behind the block wall with loose fill hemp lime to bond the block wall to the existing subterranean stone wall? I have since read that hemp lime should not be employed in below ground situations? What are people's thought on this?

    In a similar situation - basalt stone wall built into a hill (sandy soil) being the rear wall of the house - I built a conventional brick wall, single skin, in front of the stone wall having put a vertical DPC (sheet of plastic) between the stone wall and the brick wall. The gap between the 2 walls in minimum and there is no connection between the 2 walls. This was all done 25 years ago and there have been no problems since.

    In more recent times I have put EWI (standard EPS with thin film acrylic render) on to basalt/rubble infill walls with no problems and a much improved internal thermal performance.

    I have no experience with lime other than using it as the plasticiser for cement mortar and render.

    Your property sounds well located in terms climate protection and the 50cm stone walls should give a comfortable, stable internal temperature - With our house in a similar location we find that in the winter we venture out - think 'Oh - not to bad' - walk down to the road and half way down (by then exposed to the north) we turn around to go back for another jumper! Location with regard to the environment and compass makes a bigger difference than I ever appreciated before living here.


    Hi Peter. Interesting to hear your experiences. Can you expand on what EWI is please and also EPS? I am not familiar with these?
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Here area few pictures of the house:-

    South facing aspect. Note the horrible cement render splashback and zero guttering - a recipe for disaster. We will be removing all cement render and re pointing in lime and also partially wood cladding with external breathable insulation under the locally sourced wood cladding.
      Orluc resize 1 for forums.JPG
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    House in it's general setting at 810 metres in the Massif Central. Lot's of mature Oaks, Lime tree, Birch, Scots Pine.
      Orluc house setting resize for forums 2.jpg
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    This is the rear of the house which as you can see has a flat terraced area long ago cut from the hillside. Again there is no current guttering and the cement pointing and splashback is causing " issues". All to be removed. The barn door entrance is onto the 90 metre square (currently open plan) second floor. Those horrible breeze blocks are going too, to be replaced with a triple glazed panel at one side of the current French doors which are double glazed hardwood. p.s that the French estate agent not my partner Jackie !!:bigsmile:
      Orluc rear of house resize for forums.JPG
    • CommentAuthorLehobbit
    • CommentTimeSep 27th 2020 edited
     
    Another view of the house from the access driveway. We need to do some tree work to open it up at little but are reluctant to remove any of the huge and old oak trees. Maybe some judicious crown lifting. The small attached outbuilding will be having a green roof.
      Orluc view from gate 2 for forums.JPG
    • CommentAuthorEd Davies
    • CommentTimeSep 27th 2020 edited
     
    Posted By: LehobbitWe plan to excavate a channel about a metre deep along the back of the rear house wall and put a honeycombed plastic moisture barrier against the back wall and then re fill the void with gravel and drainage pipes.
    That's exactly what I was thinking of.

    Can you expand on what EWI is please and also EPS? I am not familiar with these?
    EWI = external wall insulation. Contrast with IWI = internal wall insulation as your hemp lime layer would be considered, if I understand what you have in mind.

    EPS = expanded polystyrene: plastic insulation that's not quite as insulating as PIR (like typical Kingspan or Celotex products) but has the advantage of being quite a bit more vapour open (“breathable”). Grey version has a carbon coating on the little bobbles making it more insulating than the white stuff but proportionally for insulating value more expensive so useful where space is at a premium. More flammable than PIR, too, so not so good for use in applications where it's not covered be a good fire-retardant barrier. Not to be confused with XPS = extruded polystyrene.
    •  
      CommentAuthordjh
    • CommentTimeSep 27th 2020
     
    Posted By: Ed DaviesEPS = expanded polystyrene: plastic insulation that's not quite as insulating as PIR (like typical Kingspan or Celotex products) but has the advantage of being quite a bit more vapour open (“breathable”). Grey version has a carbon coating on the little bobbles making it more insulating than the white stuff but proportionally for insulating value more expensive so useful where space is at a premium.

    It's main advantage though is that it's significantly cheaper than PIR or phenolic, even the grey version.

    More flammable than PIR, too, so not so good for use in applications where it's not covered be a good fire-retardant barrier. Not to be confused with XPS = extruded polystyrene.

    Hmm, my personal decision was not to use PIR anywhere, given it's highly toxic combustion products. It certainly needs enclosing by a fireproof barrier. Very dangerous stuff IMHO. If I had needed something with better performance than grey EPS, I would have used phenolic, such as Kingspan.
  3.  
    Lehobbit - Sorry about using the alphabet soup - I shouldn't assume people know all the abbreviations glibly scattered through this forum - re EWI and EPS - Wot Ed said !

    It s a nice place you have there. If it were mine I would be thinking about putting EWI on the back and ends and keeping the front as is for the aesthetic value. If the small attached outbuilding is going to be unheated then put EWI on the house wall inside that as well.
    I had this situation with an unheated garage and I put sheets of OSB (sideways, so 1.25M high) fixed through to the wall as additional mechanical protection.

    At the back you are right about digging down 1 meter and putting in the honeycombed plastic moisture barrier with french drain to the outside but I would put EPS EWI on the wall before the honeycombed plastic. EPS insulates even when wet and doesn't soak up water. You would need to use the standard EWI system of adhesive, EPS then adhesive plus glass mesh but the final thin film acrylic render can be omitted for underground works. This would not only give you a drier wall but a warmer one as well.

    Some will favour XPS (extruded polystyrene) under ground as it is closed cell but eventually water will seep into XPS when underground and once there will not come out. EPS on the other hand will release any water that goes in when the standing water goes. There is a study that showed, in a below ground situation, EPS out performed XPS for long term insulation value (over 15 years if I can remember)
  4.  
    Posted By: Lehobbit It's a large roof of 156m2 so slate was not affordable (we were quoted €24,000!!)


    Is your roof shaded? If not then I'd be tempted to fit roof integrated solar to a large part of the roof, allowing you to recycle some of the better slate currently on your roof. You could still insulate above, between and below the rafters to give you the necessary u values to cut your heating bill, and you'll also cut your electricity bill.

    We fitted roof integrated panels to a leaky roof consisting of large stone slates. It's been up for years and not a single leak.
    • CommentAuthorLehobbit
    • CommentTimeSep 28th 2020
     
    Hi Pile-o-Stone

    Unfortunately the roof is much worse than it looks in the images. The slate used is the horrible skinny stuff which is only about 1mm thick. Lot's of the chevrons have rotted out at the ends where the roof has been neglected. It needs proper replacement. This was a French families holiday home even in this state with a leaking and knackered roof. Beats me?
    • CommentAuthorLehobbit
    • CommentTimeSep 28th 2020
     
    Hi Peter -in- Hungary

    I hear what you are saying about the external insulation with ESP but we want to avoid synthetic materials as much as possible and go down the natural route if we can. For the roof we have sort of been forced down the route of Bac Acier simply by cost. A Bac acier sandwich roof including 120mm of insulation in PIR will be around €11,000. A new slate roof would be well over double that and does not include any insulation. We don't like the fact the the bac acier roof has non natural material for insulation, but we have to accept that we cannot stretch to a slate roof and 155 m2 of natural insulation. We will have a storage attic below the Bac acier roof with 100 to 150mm of insulation between the rafters and this will be above the bedrooms.

    The problem with the rear wall of the house is that it has been horribly rendered on the inside with cement based render. I think once this has all been removed we won't have a wall that we wish to be on view. We are not great fans of "pierre apparent" The full height of the wall that is below ground level is about 2.2metres. It's not practical to dig down on the outside by that amount and we would be worried about the wall moving and distrubance, plus the time and cost? Digging down a metre would be about the limit and even then we may hit bedrock. Part of the exterior of the house will be timber clad and this will have external wood fibre insulation underneath a breathable membrane.

    What I really want to know from this forum is the viability of using hemp lime on the walls on the inside (below ground level), especially using that Hemp block system to build a new ground floor rear wall and then infilling behind with loose hemp lime fill to bond it to the original wall. Alternatively we could shutter around 150mm of hemp lime directly against the rear stone wall. My question is will it hold up to any damp however slight? I can't see the north facing aspect getting driving rain against it as it is so sheltered at the rear by the terrace and tall tree covered hillside. Once we have guttering and proper drainage, plus a honey comb membrane on the exterior for the top metre of backfill, I cannot see how it will be really damp? The house we are renting has a cellar below with natural stone walls. They are not damp to the touch even though they are well below ground level? Anyone got any experience with hemp lime?
  5.  
    Have you e-mailed UKHempcrete.com for advice (Alex Sparrow's co.)? I am sure they will be able to give you an opinion. You talked about ''using that Hemp block system to build a new ground floor rear wall and then infilling behind with loose hemp lime fill to bond it to the original wall. ''

    As I understand it the experience of the person I spoke of was that the bond was not necessarily good. In some parts the rigidity comes from tight contact with the floor and the ceiling, not necessarily from adhesion between the hemp and the stone wall.
  6.  
    Posted By: LehobbitI hear what you are saying about the external insulation with ESP but we want to avoid synthetic materials as much as possible and go down the natural route if we can. For the roof we have sort of been forced down the route of Bac Acier simply by cost. A Bac acier sandwich roof including 120mm of insulation in PIR will be around €11,000. A new slate roof would be well over double that and does not include any insulation. We don't like the fact the the bac acier roof has non natural material for insulation,

    What about using tiles for the roof, would this give a more traditional look at a price more affordable than slate although you may have problems with the joist sizes as tiles are heavier than slates. (there are also lightweight composite 'slates' that might be worth a look)

    Posted By: LehobbitThe problem with the rear wall of the house is that it has been horribly rendered on the inside with cement based render. I think once this has all been removed we won't have a wall that we wish to be on view. We are not great fans of "pierre apparent" The full height of the wall that is below ground level is about 2.2metres. It's not practical to dig down on the outside by that amount and we would be worried about the wall moving and distrubance, plus the time and cost? Digging down a metre would be about the limit and even then we may hit bedrock. Part of the exterior of the house will be timber clad and this will have external wood fibre insulation underneath a breathable membrane.

    For the rear wall I was suggesting putting on insulation for the 1M you are digging down as once you get down 1M the soil temp is a stable 12 deg year around where as at the surface the soil will follow the air temp so there would be an advantage to insulate down 1M as you will be digging down anyway. Below ground EPS is, IMO, the best price/performance insulation available.
    I understand that you want to use natural materials, I tend to be a bit more pragmatic about material types and I have always felt that the additional effort with e.g. wood fibre with the protection needed when used externally and the implications when that protection fails makes EPS the material of choice for EWI for me given that historically it has been used for 40 years+ with much the same methods without problems.
    • CommentAuthorLehobbit
    • CommentTimeSep 29th 2020 edited
     
    Hi again. Yes we have already been in touch with them. They have offered us a consultation at £95 an hour via Skype, which we may do. Was hoping for some free advice!!
  7.  
    I've used hemp lime in our house (built circa 1752) and found it to be fantastic stuff. You can use much thicker layers than normal lime plaster and it's much warmer to the touch. I've taken out mouldy plasterboard and replaced it with lime plaster and it has always solved the damp problem.
  8.  
    Pile-o-stone, did you trowel/'glove' it on, or shutter it? From talking to my former colleague I think the 'gloved-on' bits got better adhesion than the shuttered ones, presumably (genuinely) because of the increased 'kinetic energy' possible when trowelling or 'gloving' - it becomes a bit like harling.
    •  
      CommentAuthordjh
    • CommentTimeSep 29th 2020
     
    Posted By: Nick ParsonsPile-o-stone, did you trowel/'glove' it on, or shutter it? From talking to my former colleague I think the 'gloved-on' bits got better adhesion than the shuttered ones, presumably (genuinely) because of the increased 'kinetic energy' possible when trowelling or 'gloving' - it becomes a bit like harling.

    I expect it's just like lime in that respect. So pressure/impulse, and working it in, are going to help adhesion. If there's any way to improve the surface key that would be the best way to improve adhesion I think. Maybe fasten some nails or screw in the stone, or apply an adhesive first and put the lime over that. It might be useful to put a fairly thin layer of fat lime on the wall first to make sure of the adherence, then scratch it up when leather hard and hopefully shuttered hemp-lime will adhere well to that.
    • CommentAuthorbxman
    • CommentTimeSep 29th 2020
     
    No experience of Hemp-lime I am afraid but for what it is worth

    I would endorse everything P i H says

    For the rear wall I was suggesting putting on insulation for the 1M you are digging down as once you get down 1M the soil temp is a stable 12 deg year around where as at the surface the soil will follow the air temp so there would be an advantage to insulate down 1M as you will be digging down anyway. Below ground EPS is, IMO, the best price/performance insulation available.
    I understand that you want to use natural materials, I tend to be a bit more pragmatic about material types and I have always felt that the additional effort with e.g. wood fibre with the protection needed when used externally and the implications when that protection fails makes EPS the material of choice for EWI for me given that historically it has been used for 40 years+ with much the same methods without problems.

    However I would suggest maybe using foamglas where ever you can it's inert made from waste glass products and will not absorb water in any way so ideal below ground .

    I am jealous of your property and your adventure with it. Good luck.
    • CommentAuthorLehobbit
    • CommentTimeSep 29th 2020 edited
     
    Posted By: bxmanNo experience of Hemp-lime I am afraid but for what it is worth

    I would endorse everything P i H says

    For the rear wall I was suggesting putting on insulation for the 1M you are digging down as once you get down 1M the soil temp is a stable 12 deg year around where as at the surface the soil will follow the air temp so there would be an advantage to insulate down 1M as you will be digging down anyway. Below ground EPS is, IMO, the best price/performance insulation available.
    I understand that you want to use natural materials, I tend to be a bit more pragmatic about material types and I have always felt that the additional effort with e.g. wood fibre with the protection needed when used externally and the implications when that protection fails makes EPS the material of choice for EWI for me given that historically it has been used for 40 years+ with much the same methods without problems.

    However I would suggest maybe using foamglas where ever you can it's inert made from waste glass products and will not absorb water in any way so ideal below ground .

    I am jealous of your property and your adventure with it. Good luck.


    Thank you for your comments. I wonder if we can source foam glass here in France?
  9.  
    Posted By: Nick ParsonsPile-o-stone, did you trowel/'glove' it on, or shutter it? From talking to my former colleague I think the 'gloved-on' bits got better adhesion than the shuttered ones, presumably (genuinely) because of the increased 'kinetic energy' possible when trowelling or 'gloving' - it becomes a bit like harling.


    I gloved it on as it was a bit thick and heavy for troweling (at least for me as an Amateur plasterer) and it just fell off the wall :).

    I quite enjoyed doing this as it's quite a tactile process and, with zero skills required, I roped in the wife and kids (suitably attired in goggles, gloves, etc) and we had a fun time doing the wall. I then went over it with a trowel afterwards to flatten it off a bit (which needed some shoving and was a good arm and leg workout).
  10.  
    You might also want to have a look at calcium silicate boards. The ones I'm considering for our ground floor dining room/Kitchen come in 30mm and 50mm thickness. They're breathable and are lime mortared into the wall and are used in higher humidity locations such as bathrooms, kitchens etc. Fireproof too, which is always nice to have.

    Not especially cheap though.
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