There is a contradiction within conservation where craft skills are supposedly respected without that respect being put into practice in any way shape or form often between trades and professionals eg. craftsmen doing each others work, conservators doing craftwork, professionals specifying installation methods etc.  

For most of construction history fixer masons (builders) have been the highest regarded people on site due to their extensive knowledge but nowadays this is completely reversed with skilled fixers being almost non-existent. This is so prolific that banker stonemasons who carve are held in higher regard and are considered the "experts" on site when it comes to building. And professionals completely dismissing the idea of anyone without an education having anything useful to input in the design or programming phase.

I have no real issue with this as I have met very few people with good enough knowledge or skills to challenge this current state of affairs. 

However that does not include me, I have gone to fairly extreme lengths to acquire the knowledge and experience necessary to challenge this. I have on numerous occassions noticed issues with designs, pointed them out to the designer and been promptly ignored. Eg. the SPAB guide to chimney capping is terrible, I explained why in clear detail and got rudely ignored. Simply put its a solution to rainwater management with no rainwater detailing... yes I did just say that. Its a long winded description to install Indian stone slabs upside down with terrible mortar. I have observed numerous examples of inexcusably terrible craftsmanship.  

Below are some of my observations with explanations but not necessarily specific solutions. A lot of this content is an expansion of points made on the Lime FAQ page.

Concrete is the biggest industry in the world, this is an extension of the lime industry.

10,000 years of being the most prolific building material across the world. 

There is no one solution.

In fact you can use several limes on one application. My case study for waterproofing a cellar has 13 different mortars used. Utilising several different types of lime in a number of different forms.

Putty is not best. Hot lime is not best. NHL is not best. To think this is to display an utter lack of understanding of the versatile nature of lime. 

Could you force the use of one lime for everything? Yes. 

Is this remotely sensible? No. 

Is this childishly simplistic and stubborn? Yes. 

Does it have any connection to historic limework or the science of lime? Absolutely none whatsoever.

"Putty is good for everything" The confusion about its supposed superiority comes from a number of places. The stupid Well's report, a misunderstanding of the word fine and professional laziness and obstinance. 

"Hot lime is good for everything" Only if you're an absolute lime ninja. To make an effective topcoat, hot is a challenge for instance. Most proclaimed experts are adding PP fibres and strong pozzalons, missing the point entirely. I have only made what I would consider to be a perfect hot mix on a few occassions, one that carbonates almost fully within days. Because that's the ultimate goal with hot mixed mortars used hot, to create such a perfect storm of ingredients that they rapidly draw in the carbon required and cure immediately. 

"NHL is good for everything" my main issue with NHL is the lack of lime in the mortars in comparison to the original that it will be working alongside. They are also strong and can get stronger with certain aggregates. Contain salt. Are unregulated. But that being said if you want something strong and its new, NHL is fine and for some stones like Granite and certain sandstones it can even be preferable. 

An often misunderstood solution that can cause more problems than it solves in an alarming number of applications. The most often being incorrect placement, surprisingly enough putting an underwater stream against the base of a building is not a good idea. They should be offset and below the footings as an absolute bare minimum. They may also need lining with more than fabric and assumptions should not be made in regards to where they discharge. My preference would be for them to be covered with paving and a slot drain or similar installed with additional detailing at the wall base.

Not repointing the most likely place for water ingress seems to be very popular, it would seem obvious to me that when you are repointing a wall that the ground be excavated so that the footings can be repointed and not left open so that the rain can fall down the face of the fabric and then sit at the base of the wall entering at its own leisure. The same can also be said of rendering that leaves a gap at the base of the wall similar to modern applications, surely its obvious that this is not an effective solution to shed rainwater away from the wall. The solutions to both lie in utilising alternative lime mixes and would fail should a modern putty based or hot lime mortar without any additives and fine aggregates be utilised, Especially if efforts have been made to reduce shrinkage such as PP fibres or strong pozzalons. Although it is a istake to point up stone footings that were constructed without mortar to prevent rising damp....yes rising damp is very much a problem. Contrary to what some 'lime celebrities' loudly proclaim. 

There is a fundamental difference in how one uses an air lime mortar and a water lime mortar(hydraulic). The main premise of air limes is to use as little water as possible during mixing, application and aftercare, to do otherwise is to completely miss the point of how these mortars function and to encourage lime leaching, shrinkage and friability. They need wetting down but no more than twice a week and once they are almost dry, definitely not to keep them wet to prevent shrinkage. Docking and wetting down prior to application should be done welll in advance and with penetration of water as a goal to reduce the temperature of the building units, it is not to replace the water or prevent the mortar from drying out. And during application the surface should NOT be wet to prevent penetration and dilution of the bond point.  

I would even go as far to say that if you can keep your mortar wet for a prolonged period its wrong, the purpose is after all to dry out the masonry so if it can't dry itself out...

There is a recent trend for replacing all floors in old properties with a poorly functioning "limecrete" slab with a capillary break. This has to be one of the most poorly designed and least thought out solutions I have ever come across. (see soft capping) The slab has virtually no freelime content and is often specified with aggregates which will further reduce that. It is without a doubt the worst solution utilising cementious materials for the problem, They barely breathe and are weak, its also expensive and has little to no waterstopping functionality. It would be better to make it from virtually anything else; hot lime and pozzalons, (the irony of this being that the lightweight aggregate used is often expanded clay aggregate an aluminosilicate, AKA Roman effing concrete when mixed with quicklime and a couple of other things). Weaker NHLs which breathe more. Cement based gauged with hydrated lime, again superior breathability and strength. Weak semi-dry concrete. Lightwieght concrete. Rammed earth. Lime Ash AKA gypsum floors.

My personal solution is a two part slab with no capillary break which I'm hoping to find professional support to help me develop into an applicable system. To be used in combination with a traditional yet updated version of clay waterproofing.

I would even argue that it would make more sense to cut up an existing concrete slab so that it can be lifted in sections and the capillary break introduced beneath it without replacing it with a virtually functionless and expensive "limecrete" slab. The cork edging could be installed in a simialar manner. The issues from using concrete are mitigated by the installation of the capillary break. 

As a additional note; we know less than we did. If someone specified a suspended floor just assume it was done for a reason and reinstate it. Limecrete and high or excessive groundwater is not a good idea. Clay and limecrete not a good idea etc.

In vernacular conservation there is little to no actual construction knowledge utilised, nevermind civil engineering. It is incredibly ignorant of what can be done due to the gatekeeping, touchy nature of a lot of the professionals involved. The following is in reference to the documentary about the repair of Pisa. Did they really need to spend so long coming up with such an obvious solution to the leaning Tower of Pisa? And why aren't they combining that with a longer term solution of stabilising the surrounding ground. Or installing long underground supports to spread the weight across a larger area. I'll tell you why, because a bunch of old men with little to no true experience in these types of works are making the decisions. I can't believe they kept talking about the structure as a moden one and not as one piece of masonry, the constant surprise at how it behaves was depressing. It is one solid unit bonded by exceptional mortar built as a lattice of very hard stones with a flexible core, why is this so hard to understand? It is not a stack of stones like a bloody cottage. The masons involved in the contruction used their knowledge of lime mortar and how it interacts with the stone to such an extent that frankly its insulting the way they kept saying how good they were without ANY real acknowledgement or understanding of how included in the discussion. If I had to guess I'd say that the mortar used had the same stone ground as aggregate with a few additions, slightly impure quicklime and potash, used hot. This creates a far superior bonding mortar than is assumed possible. See my mortarman page for further explanation as to why this is so effective. 

There is almost no consideration taken by a lot people who specify lime mortars and plasters in regards to the type of stone its being utilised with. This is stupid and can be very harmful to the structures. Eg. sandstone does not like lime rich mortars with the potential to lime leach. Hard stone will destroy weak mortars like modern putty based ones. Using a pure hotlime mortar with unseasoned stone will just pull all the salts that are supposed to evaporate off the face and harden it off, into itself. Clogging it up in a similar manner to the unbreathable orange mineral formation often seen on older mortars exposed to excessive water for prolonged periods, that causes spalling of both the mortar and building units. Common with brickwork, 

The list goes on...

There is incorrectly, little to no difference in how people now build with lime in comparison to modern masonry. 

Lime needs compaction for best results, how this is achieved depends on the application. And to bypass this by excessive wetting to achieve a slow cure, adding fibres or pozzolans should be avoided. Among many others. Its supposed to shrink, the art of limework is making a mortar which doesn't shrink too much because its been made with minimal water and the correct range of aggregates. And to know exactly when it needs compacting.  

Repointing is beaten back with a churn brush to achieve this, not to expose the aggregate. That is a conservation method to match aesthetic appearances taken completely out of context and overapplied. The surface should be dense and smooth, not rough and porous. The lime provides the capillary action not visible pores. The rate of convection is not altered by the surface texture and the mortar should be dry enough not to have a layer of laitance.  

Render is knocked back with a wooden float and in more extreme waterproofing cases with significantly more vigour using different tools, depending upon the application. The Roman method was to use very large wooden mallets when each layer was green. Six layers normally and each was different amounting to monlithic construction of such superior functionality some of it still exists today. 

Masonry is compacted with each placement of a building unit by using a mallet or installation techniques such as back buttering with a comb. And not a little rubber one. The mortar should be dry enough to have a point at which it cannot be compacted any further, When building its key to be able to know how much mortar to apply to achieve this. And make a mortar which can do this and not be squeezed out of the joints. It should be very difficult to remove the building unit once affixed this way and it should barely move at all. 

There are exceptions to the compaction rule. Wall hearting for instance does have to be well placed without voids but doesn't require the intense levels of compaction that facades do. Hot mixing can be done without any compaction BUT this is not easy to do. More importantly the mixes are not easy to make this tightly gauged and can often have problems with late slaking due to minimal water content.   

This is a very dangerous topic as it can be completely misunderstood. 

I will provide one good example and one bad but no more as I don't want to get sued or have people take my comments out of context. There are more in the lime FAQ's section.

Permeable resin grouts are excellent for beneath render at the base of a wall, eg. you pave with a virtually impermable stone leaving a gap against the wall which the render will cover. This allows the water to run off the render onto the paving but prevents any collection or movement of water in the render for whatever reason. Used in conjunction with a correctly installed french drain this is an excellent method of managing rainwater. 

Hempcrete, this is contrary to most of the principles of solid wall construction using lime mortars. The overriding aim is to produce a monolithic/unbroken construction with directional capillary action and matching thermal expansion rates with insulative properties that has a long lifespan due to its ability to repair itself. This is almost the opposite to that. 

Lime is not always the answer and can also be a problem. 

A lot of building facades aren't built with lime and even when they are, not the sort of lime mortars and renders produced by lime suppliers. 

This is important because these materials are designed to take on water and if they don't match one part will be damper than the other. Perpetually so in some cases. Hot limes and putties are bad for this, people install them alongside an existing mortar that is denser and quicker drying. So rainwater runs off the original and collects in the new which can't handle it. This can happen with entire walls or when patching in repairs. The wrong sand mix can also do this being have too many voids in comparison to the original. Same problem can happen inside in buildings with poor ventilation as the condensation will collect in the most porous or cold section and if it happens repeatedly it can saturate the building fabric.

NHL's made with washed sands can also retain water due to their porous nature in some scenarios. All types of mortars can do this, especially in sheltered but wet areas. 

The solution to doing this can sometimes lie with some form of barrier between materials but this can then cause other problems. But can be an effective way to prevent the transfer of moisture from a newly built extension to an existing structure if the capillary rates can't be matched. 

All masonry wants to be dry whenever possible. 

There are numerous things done to try and achieve this such as rainwater detailing like drainage or parapet coping. Rendering, limewashing and sheltercoating. Roofing details such as extended eaves and corbels. Cills with driplines. Dense stone at wall bases. And so on and so forth. 

This is by far the most important consideration to take when specifying any masonry work and is woefully ignored. Masonry should not be green and slimy, it shouldn't rot, it shouldn't have standing water on it except in a few exceptional circumstances etc. 

I see a disturbing amount of masonry specified incorrectly that has its lifespan and appearance dimished because of this. 

Masonry shouldn't be left bare if it wasn't previously, no matter how fashionable it currently is. 

No wall should be built with water allowed to freely run over its face unless its specified to do so eg. A2S2 Engineering bricks with SBR enhanced cement mortar. Even, dare I say it, the pre-existing ones. And yes some garden walls lack this attention to details but we know better now so shouldn't be doing this anymore.    

I have seen numerous reports on how soft capping is replacing hard capping due to a number of failures.

This failure is down to poor craftsmanship and mortar making not hard capping itself. Lack of compaction, preventing shrinkage, overly wet mortars, pure mixes, incorrect docking, wimpy application, incorrect docking, exposing aggregates, wrong aggregates etc. If it were cement you could just slap it on, spray it for a few days and that would be that but this is lime work. The craftsmanship of which seems to be a unicorn to most people.   

Soft capping is pure idiocy, introducing a salt rich, damp biological material to the top of a masonry wall is fundamentally stupid and I would strongly question whether the people involved in this should be anywhere near historic masonry of any sort if they don't understand the plethora of issues this will cause. I mean seriously this is so disappointing it genuinely upsets me. How can people who think this is a good idea be involved in any sort of decision making. The very same people probably contract masons to remove vegatation from masonry because its harmful.  

The common opinion is that lime works take a long time.

They don't have to. You can utilise various technigues such a green bonding your plaster layers and applying hot limewashes to uncured render. 

And you can hasten the carbonation of the mortar itself with mixing techniques and materials. 

If you don't use excessive water, yes this annoys me, then you can work all year round. And I have tested this on numerous ocassions, pushing the boundaries of when you can work, far beyond what people would expect. A snowy mountain in December... 

There is no historical precedent for it taking a long time or being restricted by the weather. So I do wonder if this is partially down to the highly unprofessional attitude of the type of people who like working on old properties. Not the best ones but the loudest and most prolific, coupled with lime suppliers trying to avoid their products failing and putty being in vogue since the Well's report, Which would likely fail in Winter. Its almost as coincidental as there never being any problems in the world during August that would require politicians, media or business to cut short their holidays. And if I really want to get into it, then us being in the final stages of an Empire probably has a lot to do with it too. 

If you don't get this point, don't work with lime. 

Lime dries by wind on its surface and as it dries, the lime pulls more water through its micropores. This is relevant both inside and out. 

The rate of this capillary action is affected by how much lime is in the mortar. This is why traditional plasters are layered with more lime to the surface and why its more effective to use limewash over render. 

In some cases when you get this wrong the pull of the deeper coats with a higher lime content can hold moisture in the wall.

One of the many reasons NHL's aren't recommended. (see the picture opposite which is NHL 3,5 over an original lime rich air lime mortar)

I've touched upon this subject a few times but wanted to stress it further.

An old property is not like a modern one, they require a far more fastidious approach to maintaining them as they can be irreversibly damaged unlike modern properties, which are fairly easy to fix. 

Pentrative damp can sometimes never be removed, limes capillary action is only effective to about 100mm and most traditonal cottages have 600mm walls. 

If you allow impurities such as salt to moved into the building from whatever source eg. an unlit chimney or a leak which runs over brickwork. Then this can react with the lime mortar or stones natural binder forming minerals or leaving salt deposits which will have a detrimental effect on the building. And require the complete replacement of certain sections. 

There are many things that need doing and a lot of them are dirty and unpleasant so don't get done eg. repointing wall bases below the ground or clearing drains and guttering. Painting wood or masonry. 

Maintenance is easy to do and cheap in comparison to the problems that ignoring it can cause.

This happens a lot and should be a serious consideration with older properties as there is often no obvious correct answer and a lot of people just want paying without any chance of financial liablity or damage to their reputation. EG. an Archtitect will often specify copy/paste solutions that are widespread such as limecrete or EWI when a more bespoke but 'unproven' method would be far superior. A builder will recommend what they know, eg. plasterer background will want to plaster everything, a stonemason will want to clean and repair everything, a joiner will want to build false walls etc. 

This is a reiteration of don't be cheap and lazy, hire Chartered professionals and a number of specialist craftspeople. Pictures can look impressive, very easily, Old properties functioning well, not so easy.