Lime in sections | Heritage Lane

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Gypsum everywhere!

Tday gypsum is used everywhere, by trades people who call themselves plasterers, which is interesting considering gypsum plaster can be applied easily by anyone who cares to try because it's so easy to use,

easy to mix, easy to apply, and easy to make it look flat. And having tried it many times We were amazed at how easy it really is! Alledgedly many even claim to be qualified to use this chidrens material 🤣

So what is Gypsum?

Gypsum is 'Calcium Sulphate Dihydrate' and Calcium Sulphate Dihydrate is a Hygroscopic salt. Sodium Chloride is also a hygroscopic salt and sodium Chloride is in you Kitchen cupboards, labeled up as Tabe Salt.

What happens if you leave your table salt out, uncovered, in the kitchen?

Your table salt absorbs all the moisture in the air and it sets hard, because it's hygroscopic (the armchair experts call it 'hyDroscopic', which is something that doesn't even exist, but God loves a tryer! 🤣. But, in fairness to them, the word 'hydro' is associated with water so obviously there's nothing wrong with their intelligence whatsoever! 🤣🤣🤣

Seeing the obvious yet?

Gypsum plaster will absorb and retain any atmospheric moisture, so it's completely useless in older properties where moisture is naturally present, plus don't forget that salts ere electrically conductive, meaning that the Damp 'special people' will always get a reading from there electrically operated two pronged machines when they stick them into your internal decorating!

So in summary

Gypsum plaster is just wrong for period properties.
Gypsum plaster holds dampness
Gypsum walls will obviously appear to be damp.
The 'special people' take lots of money from you for nothing, (see 'the power of nightmares' on our"rising damp" page.)
The 'special people' will tell you that your DPC has failed (without even ever seeing it.) £££'s more completely unnecessary costs to you.
Damp walls are cold walls in winter months, obviously affecting your heating costs. Meaning they are unnecessarily expensive because you have to heat cold walls.

Beautiful Lime plaster!

Lime plaster doesn't bring you all the false promises that gypsum does.

Lime plaster will not eliminate your indoor atmospheric moisture, but neither will it retain it, because lime is naturally high in capillarity meaning it releases moisture readily, and in fact it manages that moisture release for you.

Lime has natural anti bacterial qualities meaning no mould growths, no fungal growths, no germ spreading, therefore resulting in a healthier home environment for all of the occupiers of that home.

Simply put :- lime is far superior!

Lime vs cement?

Cement is unforgiving and always cracks, regardless of the building"s age.

Lime is forgiving, whilst retaining flexibility once cured, but lime is also self healing in the unkikely event of any slight cracking forming.

Unfortunately far too many people didn't study sciences too well, and today we see far too much of a "lime vs cement" type thinking, along with new found "armchair experts" who've been reading other "new found armchair experts' opinions online and / or watching too many new found DIY armchair experts creating youtube videos.

Despite schools still pumping out three states of matter; solids, liquids and gasses, and whilst every building is a complex mix of all three of those, there is also a huge involvement with English, Maths, and Engineering.

Once we expand physics further into quantum, Particle, and Atomic Physics we find that there is actually nothing on earth that is truly solid becase Atoms are in a perpetual state of electro magnetic energy but because they are basically invisible to the naked eye, and even to most microscopes, they tend to get forgotten about in day to day life.

So no building is in fact solid. (See our Building Sciences page also for more info)

Further to this, natural humidity and temperature variations cause differential expansion and contraction of each and every individual element used in the construction and use of every building.

So buildings do move, and on a day by day, hour by hour, minute by minute basis.

Lime is a natural earth product, and when we use it, for example as an external render mix, we mix water with the lime and the aggregate, we then apply that render mix to to a substrate where then the water content from the mix naturally evaporates out into the atmosphere, and CO² is absorbed from the atmosphere into the lime, and this is how lime products dry and harden.

If any cracks might appear, the lime just waits until it rains again. That rain gets into those slight cracks, re-evaporates again, CO² is re-absorbed again, lime is dry and hardened again.

Ordinary Portland Cement (OPC) (or "cement") sets through a chemical ptocess with the water meaning once it's set, it's set. then colder temps arrive; frosty winter mornings where the water trapped inside the set OPC freezes.

When water freezes it changes from a liquid state of matter to a "solid" state of matter, but in doing so it expands in volume by approx 9-11%, and this is where the damage occurs, only now it's done, there's no self healing as there is with lime because the added chemicals don't allow for that.

Now is another very important part which a huge amount of today's so called online "armchair experts" simply do not know.

There are a vast amount of confusing names today for lime:

Hydrated lime
Quick lime
Fat lime
Lime putty
Hot lime
Hydraulic lime

Non hydraulic lime

Air lime

To name a few.

The main two you eally need to know about are hydraulic lime and non hydraulic lime.

Hydraulic lime is similar to OPC in that it uses additives to create a set with water.

Non hydraulic lime is pure natural lime which drys and hardens by evaporation of the water and absorption of the CO²

So a non hydraulic lime render mix is the better of the two options as Non hydraulic Lime provides very good capillarity which is vital for managing moisture transfer, and flexibility in older buildings whereas Hydraulic limes are used for limecrete / screeded floors or other subterranean situations where the presence of ground water is constant and therefore the risk of freezing is greater, plus Hydraulic Lime mixes are also resistant to earth salts.

Lime is also a natural anti bacterial agent meaning less chances for bacterias, mo, and fungal growths to occur = more healthy home.

Lime is not just simply another building material, and it's most certainly not a new material. Evidence of it's use in buildings stretches as far back as 10,000 years ago!

At Heritage Lane, we understand the importance of using traditional lime products in buildings to maintain the authenticity, functionality and charm of properties, and architectural features of any historic building.

Restoration & Conservation of beautiful period buildings isn't just a job to us, it's been a lifelong passion.

Lime mortars, lime plasters, lime renders, lime screeds, limecretes and limewashes provide for good moisture vapour permeability which is always important in period buildings.

Non Hydraulic Lime plasters (which we'll now just call Air Lime because when we get onto NHL limes, confusion only worsens) used internally can also provide thermal insulation when mixed with other correct natural elements.

So to recap: Air lime remains flexible and is also 'self healing'; whereas cement based products simply crack as buildings move, because ?they are very dense materials which have high compressive strengths.

But because Air lime cures through evaporation and carbonation; it actually absorbs atmospheric CO² from. the air which causes it to set, (hence Air Lime) therefore it removes CO² from the atmosphere meaning that if any cracks do appear, those cracks will absorb more moisture as it asvitbrains again and that moisture will be re-evaporated again and more CO² will then absorbed again. Meaning Lime is helping the planet!

Further to all of this; lime itself posesses natural antibacterial properties that help to combat and reduce the spread of bacteria, germs, and mould/fungal growth within the home.

Knowing the correct type of lime to use for a specific task is important and this is where we can help.

Today we see a plethora of names used for lime products, including:

1 Quick lime

2 Lime kibble

3 Hot lime

4 Fat lime

5 Lime putty

6 Hydrated lime

7 Hydraulic lime

8 NHL 2.0

9 NHL 3.5

10 NHL 5.0

So lot's of confusion!

We'll go backwards: NHL stands for Natural Hydraulic Lime, but for now we'll just stick with ĺ

HYDRAULIC LIME

L so to keep it as easy as possible (NOTE: NHL can easily be confused for both non hydraulic and natural hydraulic limes)

We have AIR LIMES ( No.s 1 to 6 above )

& HYDRAULIC LIMES. ( No.s 7 to 10 above)

Today's Natural Hdraulic Limes (NHL's) limes were introduced in the 1990's in the pre-mixed bags we see today; before that we had to create our own Hydraulic lime mixes by introducing 'pozzolanic' materials to AIR LIME mixes.

The numbers shown on HYDRAULIC LIME bags relate to their final "compressive strength" measured after 28 days of setting time, in the same way as Ordinary Portland Cement (OPC; commonly called 'cement') is measured @28 days.

The units of measurement used are 'Pascals' but as 1 Pascal is equal to 1 Newton per mm² we generally just say 2 Newtons, 3.5 Newtons & 5 Newtons.

We use Newtons in the UK simply becsuse that is a measurement more commonly used and understood in the UK. Cement) varies in compressive strength, generally between 30 N/mm² and 53 N/mm²

Whereas HYDRAULIC LIMES obviously also vary in compressive strengths: between 2 & 5 N/mm², however there has always been some "discussion" over whether or not NHL's continue to 'strengthen' over time due to more moisture/ water contact over time. However we have never seen any evidence to prove this, so.that's just another "old wives tale" in our opinion until proven otherwise. (You'll soon realise that older buildings bring a lot of old wives tales with them and a lot of people today still try to tell a lot of of these old tales).

Maybe some of the armchair experts got a bit confused between natural lime and 'Roman concrete' which is a very diifferent, yet still very ingenious science, and very useful if you want to tie your ships up in sea water. Not exactly needed in or on your house though

So to quickly finish up:

Air Limes (No's 1 to 6) where moisture permeability & flexibility is required.

Hydraulic Limes (No.s 7 to 10) where strength is required.

And don't forget that Hydraulic limes do also posess some moisture permeability, but lower than Air Limes because they are a very much more dense and harder material once set, so it is important to consider this, and consider it intelligently when choosing the correct lime for a particular task.