Mixing and using lime mortar and why it's a great idea to take a natural building diploma!

Whenever we take a trip to the Pointe d'Agon to collect oyster shells for the chickens we pass by an area called Les Fours au Chaux - 19th century lime kilns, these are dotted all over this coast and were apparently mainly for manufacturing lime for agricultural use. Ironically lime production for building work historically used oyster shell. For an idea of how long construction and lime have been associated, the first lime used for building was in the Ancient Kingdom of Anatolia, the region that is now eastern Turkey and the foundations studied date from around 14,000 years ago.

The oyster beds from the Pointe d'Agon 

Once the food of the poor, the now rare deep sea oysters are harvested here only for a few weeks at the end of November and kept 'in captivity' before ending up on the New Year's dinner tables of Paris.

Introduction

When I moved back to England to study for my doctorate we bought a 1930s house in great need of repair some of which was to do with the masonry of the building. At the time I was also supplementing my research grant with some teaching at a local college (Maths and IT) and it was here that I found that there was an evening course in bricklaying for D.I.Y. Keen to acquire new skills, I enrolled for this and over the next eighteen months or so I became acquainted with some of the practical techniques of this fascinating trade. Our instructor was a professional builder and the tips and suggestions he made to me and my classmates regarding our own specific home projects were invaluable. Although Natural Building per se was still in its infancy or rather rebirth, we were very lucky in our instructor. One of the most important for me and avant garde for a mainstream building course, was his his stressing of the use, where possible, of lime mortar. We used this in class and became well acquainted with the medium. On finding out that I wanted to replace an ugly 1960’s fireplace with a cast iron Art Nouveau one he immediately cautioned me not to use the very expensive commercial  fire cement but to opt for a ‘soft’ lime mortar mix to fit the new fire-back, Following his advice I was able to undertake the job at a fraction of the cost through using his recommendation and it worked perfectly. In fact the money I saved through not having to purchase the expensive refractory cement more than paid for the evening classes!

If you have a project that requires bricklaying or stonework and you want to do it yourself then I would highly recommend contacting your local colleges or schools to see if such a course exists. Nowadays you may be lucky and find they have an actual designated Natural Building Course or Workshop, or at least a sympathetic tutor like ours, you won’t be disappointed and it may be a start of a brilliant new career.

Whilst my knowledge of lime mortars is in no way as extensive as I would like, I have never found that the mortars I have mixed and used have done anything detrimental to the structure of the buildings. For further information on specific uses of lime mortars, I have included three of my favourite sites at the end of this post.

I’ve used lime mortar a lot in our present house firstly because it is obviously appropriate to a 300 year building, as it is sympathetic to the original  build of stone laid on a bed of clay mortar, secondly because in the mortar mixes I have used it will never be stronger than the stone of the house and thirdly when used in wall construction, the wall is able to ‘breathe’, essential for the 70cm (27”) thick walls that we have here. Clay mortars were very popular in the 15th century and were still used in vernacular houses and buildings in the 18th century.

Battle scars Our two workshops showing the variety of 'make do and mend' pointing that the house front has suffered over the centuries as it has weathered the various bellicose attempts of man. To us this is all about the persona and age of the house, so unless the repairs have been of later date and thus of cement, we have left them alone. In keeping with tradition and harmony, Sue of course laid our front garden stones on a bed of lime mortar.

Fenêtre meurtrière - literally murder window or rather arrow-slit window, not only bears witness to the width of our walls but how much an 18th century French farmer's house was his castle. These windows allowed the occupants a wide field of view and thus fire, whilst being protected by the walls with a formidable stone shield.

A Word About Natural Hydraulic Lime

Sea shells, chalk and limestone are all forms of calcium carbonate, when these substances are crushed and heated in a kiln between 800ºC –1 000ºC the carbon dioxide in the compound is driven off leaving solid calcium oxide(quicklime).

Adding water to the cooled medium results in an exothermic reaction and produces calcium hydroxide which subsequently, if left exposed to the air, will absorb carbon dioxide to form once again calcium carbonate. Adding sand to the calcium hydroxide produces a mortar known and used for thousands of years. If the limestone is not pure but contains impurities of  clay then during the heating process the calcium will react with the clay to form compounds called silicates which will set with the addition of water. Not all of the calcium will be in the silicate form, there will still remain some calcium hydroxide, which will set by the carbonation process. Thus mortars of different strengths and setting times can be produced. depending on the level of the impurities.

There exists a classification for Natural Hydraulic Limes which describes their performance due to the level of impurities. Namely: feebly hydraulic NHL 2, moderately hydraulic NHL 3.5 and eminently hydraulic NHL 5. The higher the number, the faster the setting time and the harder the resulting mortar.

Mixing the Mortar by 'Feel'

If I was to use the word Art in connection with lime, it would no doubt conjure up an image of High Renaissance fresco but in effect my meaning here is much more prosaic and refers to the mixing of mortar. Or rather it has become so, as over previous decades we have been taught to devalue what was an art or at least artisan, down to the level of manual labour. There is as much of science and art in getting mortar right as in any other endeavour, which is why no Mediaeval cathedral ever carried a ten year roofing guarantee.

From my experience with fitting the fireplaces I knew that a weak mortar mix would be suitable for the temperatures the storage heater wall was to encounter and I decided to use a natural hydraulic lime in the mortar (NHL 3.5). mixed with a sharp sand in the ratio of 6 parts sand to 1 part lime.

Because my quantities of mortar were small I mixed it by hand in a mortar mixing tub which could then be carried into the house.

The first thing to do was to accurately measure the correct proportions of sand and lime.

That done, I dry mixed them to produce an evenly coloured, lump-free mix. This stage is important because I wanted the lime to coat all the particles of sand.

Once satisfied with my dry mix, I added water a small amount at a time and with each addition, continued with the mixing.

The water needed to be evenly distributed throughout the mix so it was important to make sure that the lime/sand mixture in the corners of the mixing tub were moved to the centre.

As the quantity of water was slowly increased, the mortar became more homogeneous and the feel of it on the mixing spade changed. It was at this stage that I stopped and tested the mortar with a trowel.

You do not want the mortar to be like a slurry, but one ought to be able to slice a sausage-shaped piece with two cuts of the trowel which can then be lifted onto the trowel, it should still retain its shape and yet have an elastic appearance when shaken (this and all the steps above are shown in the first film below).

Frankly, I find this to be a very subjective operation and this ’feel’ for a good mortar was one of the first things I learned in my evening class. Nevertheless, the too runny, slurry stage would be self evident.

Bear in mind that the mortar is there to keep the stones apart so it must have some ability to retain a shape but be sufficiently workable that when the stone is laid upon a bed of it, it will form a joint and support the stone.

In Conclusion

Lime mortar is a wonderful medium to work with and a must if you have an old house or building to work on. In the following two films you will see a demonstration of me mixing the mortar, as in the above paragraph, by 'feel' for my recent storage heater project and in the second film I'm also pointing the wall of our barn.

Now if you'd like to sit back and watch the films.


I would certainly recommend the following sites:-

http://www.buildingconservation.com/articles/articles.htm#limemortars for more information on the use of lime mortars in restoration work,

http://www.naturalhydrauliclime.net/FAQs.html for a contemporary review of the applications of the medium and

http://www.stastier.co.uk for comprehensive technical information on the performance of mortars made using lime-based products.

If you've enjoyed this article and found it useful please feel free to share it or to comment and/or make observations. All the very best and until next time,

Andy

© Andy Colley 2014

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Home-made strawcrete and stone storage heater Part 2 - building the wall

Looking backwards to go forward, our introduction to storage heaters, came about because we moved down to England from Scotland and bought a wonderful ruin of a 1930’s semi, which had been subject to a whole host of abandoned heating systems, spanning several decades, one of which was an electric storage heater. The start of this project, creating the strawcrete pad can be found here

Previous experience with storage heaters and why we decided to make our own

 

In the front downstairs room of the house, which was to become our dining room, there was was an electric storage heater. This was powered with a low tarif supply but as far as we were concerned it was ugly and inefficient, being placed on the wall between us and the neighbour. We had already decided to remove the sixties era fireplace in this room and replace it with a  cast iron Art Nouveau one we had bought from a builder and open up the chimney.

At the same time the storage heater would be moved upstairs  to a spacious front bedroom, with fine views of Warwick castle’s firework displays, great acoustics for its concerts and which we intended to use as a sitting room. Its function would be to supplement the superb original 30's Art Deco bedroom fireplace. To do this, the heater was isolated from the power supply and dismantled.

If you’ve never seen  what's inside one of these heaters then you ain’t missing much. Basically, they comprise an electrical resistance, running between heavy bricks. The heat output being regulated by a moveable flap to control the warmed air leaving the unit.

The inside rear wall is covered with a pad of insulation. A word of caution: Asbestos was often used as the insulating material in storage heaters and although you will see on many professional websites, dates of 1970 and 1980 quoted as marking the end of its use, you really need to find out exactly if the model you have contains Asbestos before you start taking it apart. Be warned that further to the obvious dangers of Asbestos, this form of insulation, when old can become powdery and thus ever more hazardous to the lungs. It is also of tantamount importance to ascertain if and when Asbestos was banned for use in household appliances/building materials in your particular country of residence. For example, when we moved to our present ruin, here in France, we found that the roofing material on an old abandoned rabbit hutch, attached to a Bread Oven in the garden, contained Asbestos but thankfully,  there were disposal procedures in place, which we could follow to rid ourselves of it.

Far left showing rabbit hutches roof cover, thus prior to Asbestos removal and right a couple of years later on.

 

The key point of our old storage heater’s relocation was that it was to be placed against the internal brick wall of the upstairs room which incidentally led directly onto the stair well. Over a period of days after reconnecting the heater in its new room, we began to notice that this wall had started to store heat as well, such that as one ascended the stairs from the entrance hall, one could feel that there was a significant amount of heat emitted. So although we had known that locating it on an inner wall made sense, we got a much greater benefit from the heater than we’d originally expected. This was a valuable lesson to us of how useful it was to be able to store heat. The means of supply (electricity) was certainly not ideal but the way in which a house could benefit from the simple method of charging up a mass with heat and letting convection do its stuff, was.

Fast forward 20 years and back to our non-toxic storage heater, by appointment to the genius loci

It took about four or five days for the strawcrete to start to feel firm, I was still able to dig into the surface with my fingernail and the surface still felt damp. Nevertheless, I decided to remove the shuttering from around the pad so as to expose more faces to the drier air in the kitchen. 

I also decided to turn the pad upside down exposing the smooth bottom face to the air and I laid the pad onto an old wire shelf from an oven so that air could circulate freely around it.

 
 

After a further seven days, the strawcrete felt firm and resisted my finger nail, it also felt considerably lighter. If you compare the colour with the little pure lime sample you are immediately struck by the warm golden colour the straw has imparted to the lime, something we exploited when we used strawcrete as the foundation layer for our hemp and lime insulated walls in our kitchen.

Work could then progress on making the wall. 

The first thing I did was move the stove off its plinth and sweep the chimney, I’ll describe this exercise in another post. 

 

Next I put the strawcrete into position on the tiled surface, the smooth, flat side down. I had decided to fit shuttering on three sides of the plinth to act as a guide for laying the stones and to prevent excess mortar from the joints from dropping into the gap between the rear wall of the heatsink and the lounge wall. I used chipboard sheets recuperated from pallets for this. The rear wall was a coated sheet but the side walls were bare of any such coating and thus I covered these with a layer of polythene so as not to  draw moisture from the mortar. Across the front elevation I screwed two narrow strips of pallet wood so as to allow me access for laying the stones. 

 

We have plenty of stones in the garden, some are from the house where we have removed parts of walls for windows and doors and some have been dug up over the years of our gardening. I needed stones that had ‘flat’ faces and were fairly regular in shape. The selected stones were cleaned of any soil or clay using a scrubbing brush and water. 

 

Prior to laying the stones in mortar, I first tried various selected ones, altering their orientation until I felt I had achieved the best fit, then removing them and laying them to one side in the same configuration. I’d decided that any large gaps between the stones would be filled with mortar and small stones. The other point in the construction was to lay longer stones front to back so as to conduct heat into the body of the wall, thus certain ones were selected to go onto the next layer. This also would make a strong bond within the wall i.e. there would be little or no mortar seam running continuously vertically down the wall. 

P.S. Extra repurposing tip - see the natty overall - we found a laundress who has a market stall, on it she sells old company overalls when they are 'past their sell-by-date'. They are really good quality and very cheap. We even once got a life-boat man's suit, which was great for heavy building work - and really good in wet weather!'

The mixing of the lime mortar and the laying of the stones and testing of the new storage heater will be dealt with in a separate blog.

Left -  another great find for our old house, this time at a yard sale, it replaced a sadly defunct Rayburn anthracite heater with a burnt-out back boiler.

The continuation of this project can be found here

If you've enjoyed this article and found it useful please feel free to share it or to comment and/or make observations. All the very best and until next time,

Andy

© Andy Colley 2014

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Home-made low-cost stove night storage heater from strawcrete and stone

For some time we have been toying with the idea of changing the heating system in our sitting room and even considered starting over from scratch and making a rocket mass heater. However, we actually have a fully functioning and useful Godin in there, which it would be a shame to part with. To this end we have decided that it would be quicker and more economical to actually work with what we already have and build what is known as a 'night storage heater'. thermal wall or heat sink at the back of our stove.

Introduction

Our house is heated  entirely by wood-fired appliances: in our kitchen we have a clean-burn wood-burning cooker which by convection heats the rooms above.

The walls, as you can see we insulated, in the kitchen with chopped straw and lime and then on top a layer of hemp and lime. Paradoxically, if we had left the space behind the cooker and the Godin bare we would have had a natural heat sink ready made. However, this is a 300 year old vernacular farm house and the bare walls, unlike the section over the fireplace were not particularly decorative and were never meant to be exposed to view. In the past they would have been whitewashed with lime, probably on a yearly basis.

The cooker is set partly into a huge granite fireplace which itself acts as a heat sink, thus providing the room with some heat even when the cooker isn’t lit. Thus, I have been thinking how I could create something similar in the sitting room.

In our sitting room we have a small Godin stove, which we bought second hand some 16 years ago now and it is on this

that I need to focus my attention before the arrival of Winter. The stove works really well, even though it is primarily set to burn coal and even in the coldest periods will rapidly heat the room. The only real problem with it is the room gets too hot resulting in us letting it burn itself out and then having to relight it as the temperature drops.

What I want to do is store some of the heat emitted by the stove and to let it  transfer its stored heat as the room temperature falls – exactly as a night storage radiator works.

To this end I have decided to build a heat-retaining wall behind the stove. I am planning to make it very economically entirely of stone from the garden and using a lime mortar in the construction. I estimate the material cost to be somewhere in the region of between 5-10 Euros, which at the present rate of exchange is approximately  £4-8  or $6-13 US

Design

The stove stands on a tiled plinth, the plinth is laid on a  foundation on the ground beneath the suspended wooden floor.

To avoid removing the tiles I chose to build the wall on a strawcrete pad , this to furnish a ‘softer’ interface between the tiles and the walls and to ensure minimum heat loss from the wall by conduction into the plinth.

I had initially thought of building the wall in an adjoining stable and transporting it, still in its’ shuttering, into the lounge. I rejected this idea when I realised that the completed wall would weigh in the region of 180-200 kg.

The 'soft' lime mortar to be used between the stones will withstand the elevated temperatures.

Materials

Strawcrete: made from chopped straw mixed with a lime mortar. I had used strawcrete before as an insulation material on the interior walls of our kitchen. One of our outbuildings had a loft full of straw, this I chopped using a modified lawnmower. The strawcrete made from this material made a significant difference to the warmth of the kitchen and the following summer we plastered the entire kitchen walls with hempcrete on top of the straw.

We now buy the straw from a local organic dairy farmer to use in our hen houses. The long stalks were unsuitable for the strawcrete and needed to be chopped into shorter lengths. Some time ago I made a guillotine from some steel scrap to chop up old fruit crates for kindling. I found this could chop the straw after I had ground the blade to a more acute angle

You can find the film on how I made this guillotine from scrap metal here

Stone: The stones used are those which have already been used in the walls of the house and have been removed in the construction of doorways and windows.

Lime: I use hydrated lime NHL 3.5 

Safety gear: Although hydrated lime is much less aggressive than aerated, it will sting if you get it on your skin or worse still, in your eyes. You should therefore provide yourself with a pair of thick rubber gloves and a pair of eye goggles. It is also a good idea to keep a bottle of clean water on hand just in case of any slip ups, so as to wash off any splashes of lime.

Quantities

When working with natural building materials one of the first things you notice is that they are not uniform. This was something we were very much aware of when insulating our house walls and floors with linen, hemp and straw, on no day were either the mix quantities nor the elasticity of the mortars the same. They were dependent on humidity levels in the air, ambient temperatures out and inside and the different batches of the raw materials. There is obviously certain quantities one can work to but be aware that you need to get a feel for these materials as you go along and that, in particular the quantities of water used will not always be the same. However, take your time, work slowly and enjoy being in tune with the organic qualities of natural building.

We found in general when we worked on our house that the quantities of linen, hemp and straw to water and lime were pretty much the same. They were as follows:

1 bucket of lime (in a 35kg bag or 77 lbs of lime, there are just over 5½ buckets)
1 kilo (2.2 lbs) of straw, hemp or linen
6 litres (8¾ Imperial pints) (1.32 Gallons US) of water

Construction

The first stage was to make the strawcrete pad.

I constructed a wooden mould to the required size and lined it with a thin polythene sheet.

Next I mixed a mortar of lime and water.

I kept slowly adding water to the lime until the mix had the consistency of a batter, you will see this more clearly in the film.

Once this was mixed to a smooth consistency, I added the chopped straw.

As with the water, I added the straw little by little, mixing it into the liquid with each addition.

I was seeking the stage where there was no longer any liquid lime left in the mixing receptacle and all the pieces of  straw were coated with the lime mortar.



The mix could then be transferred into the mould, ensuring that strawcrete was tamped into the corners and along the bottom edges of the mould.

In between the addition of strawcrete the mix in the mould was tamped down using a wooden block.

Once full the excess strawcrete was scraped off using a straight piece of wood and the pad was left to dry.

Thus stage one of the storage heater is completed, the rest will be built in situ, follow this link for: Part 2 Building the Wall Now if you'd like to, sit back and watch the film.

If you have enjoyed this post and found it useful, feel free to share it, comment, ask questions or relate your own experience of using strawcrete. Hope to see you for part two and in the meantime all the best from Normandie,
Andy

© Andy Colley 2014

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How to compost urine using a straw bale. Dry toilets for all climates.

The Piddleposter

 

A great way to process dry toilet liquid for around 6 euros or 5 dollars worth of materials. 

Whether you're a homesteader/smallholder looking to cut your water consumption or someone who just wants not to have to take off muddy boots when needing to use the bathroom.....

 
...even though the cows may have something to say about you pinching their bedding.

Introduction

 

A few months ago I received a question regarding the practicality of using a dry toilet in a really cold climate.

My thoughts on this are as follows:

The solid waste from our two-bucket dry toilet system would still go into the composter, I would advise the use of larger amounts of straw to act as an insulator as well as furnishing the carbon necessary for the bacteria to work. Even if the temperatures are very low, as soon as Spring temperatures arrive, the composting process would speed up and I would expect after the passage of two years for the compost bin contents to be completely transformed. I would have said that if one already has a climate able to compost vegetable matter/ garden waste then there will be no problem with that of the toilet contents. 
 

 

The liquid waste would probably be harder to dispose. Ordinarily, our urine is diluted with grey water from the house and then poured around the garden. When the temperatures are below zero I do see a problem with the frozen ground being unable to absorb this. Fortunately for us the cold spells do not last too long and normally the soil in the more protected areas of the garden are still porous.

I realise that for people living with longer, colder Winters the liquid waste would become a burden. So, my idea is to make a composter specifically for handling “neat” urine and capable of producing a valuable compost at the end of its processing.

The straw bale composter

Human urine is 95% water the rest is a rich mixture of chemicals the largest proportion being nitrogen. To make good garden compost you need a Carbon to Nitrogen ratio of about 30:1 and so the almost total carbon content of straw makes it an ideal companion in the compost bin.

This is an idea becoming more commonly seen at outside public events as no drainage for the liquid is required. The toilet can comprise of an enclosure with a seat if needed and an appropriately placed straw bale to receive the liquid direct from source.

French designers Faltazi have come up with an easily attached folded polypropylene or stainless steel 'funnel' so as to produce an ecological pissoire. The funnels are pushed into the sides of a straw bale at the appropriate height for men. http://uritonnoir.faltazi.com/en/

My experiment was to make a suitable container for a straw bale and empty the liquid waste from its receptacle onto it every day and see what happens to the urine and the straw.

The Design.

Obviously the compost bin has to fit around a straw bale. The standard bales in Europe are now huge cylinders and are designed to be mechanically lifted and dispersed throughout the farmer's barns. 

The organic farm where we buy our grain for our birds has these same sized home-grown organic straw bales and he uses one each morning and night for the bedding of his 50 head Normandy herd. 

Even so he has other livestock areas where he only uses part-bales. If we give the farmer 24 hours notice he can take a part-bale and re-roll it to a more manageable size. This is so it will fit into the rear of our estate car/station wagon, even then it is still quite a push to manhandle it into place. For 5 euros or 6 dollars we got this bale with enough left over in the deal to keep the Hen Houses supplied for several months. So for a small initial sum you can end up with some great and truly organic compost! You will probably have an organic farmers' register for your area, so check out the dairy or other livestock farms and see what they have on offer. Mixed arable farms will also have straw and again I would always go for a certified organic farm, where you can be assured of them not using chemical sprays and/or synthetic fertilisers.

These bales when laid on their sides in fields will shed rainwater for some considerable time, a desirable feature for the farmer but not for the urine composter hence, the bale has to stand on its end to expose the more porous part of the bale uppermost when in the composter.

 










The link for the design and construction of the compost bin on the left can be found here:
Pallet wood compost bin 


If you've seen my other compost bin design you will know of my sliding wall plank system that I developed to ensure easy access for emptying and the facility to exchange rotten planks with new ones. For the new bin I opted for only the front elevation to be of the sliding plank format, the other three walls were to be pre-made in the workshop. This would still mean that the wall panels would be easy enough to carry into the garden for assembly on site.

The cylindrical straw bale has a height of 120cm. Perfect for my needs as the standard pallet plank is exactly this length.

A waterproof lid fits on top of the container to ensure weather protection.

Fabrication

The three pre-constructed walls were made by nailing pallet planks to top and bottom horizontal rails. The wooden rails of each wall were longer than the wall width. This protruding portion fitted over or under the other walls' rail, a clearance hole was drilled through the two rails and a threaded bar was inserted. Nuts on the threaded bar were tightened once the walls were in position. 
 

On the front elevation of each side wall was a vertical post running from top to bottom to which the spacer rails were screwed and onto these were screwed the retaining rails. The resultant gap between the post and the retaining rail had to be enough to allow the wall planks to pass.

One important point is that the upper rails of the side walls projected beyond the rear wall of the composter, this to provide the pivot point for the lid.

Here is the step-by-step film showing the construction:

All the best and thanks for dropping by. Feel free to comment ask for information and/or share this article.

Cheers, Andy

© Andy Colley 2014

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