Lime mortar

[Adam W.]

@pe2dave

Measured or regulated.

Measure the components of the mortar by volume, traditionally done in wooden forms.

Gauged brickwork is a very precise method of brickwork and is characterised by bright red soft bricks and a very fine white mortar joint. They also use gauged brickwork to produce ornamental niches and other fancy stuff.

 

[pe2dave]

Ah! I gauged it be about .....

 

[Jake]

The bricks are soft so they can be rubbed to size to allow the fine mortar joint.

 

[stuckinthemud]

Thank you all, I found my local builders merchant sold 25kg bags for £12, as well as small bags for £2, bought the big bag but its probably double what I need, just more cost effective, although I hate the waste. Just need to get on with it

 

[Mike.R]

I'm late to this thread but i'd recommend, Lime in Building by Jane Schofield as an excellent beginners/intermediate guide to lime..... in building.
It's only a fiver but don't let that put you off.

https://www.blackdogpress.co.uk/product/lime-in-building-a-practical-guide-by-jane-schofield

 

[stuckinthemud]

Thank you for the advice, especially re consistency, I am bucket mixing, so no chopping and crushing, I am struggling a bit withe the dye, I didn't realise the mortar had faded where it corroded at the apex, so, even though I got a pretty good match at the wall base I am having to hack out and point a bigger area than I first intended just to get the colour more uniform. This stuff is so much nicer to work with than cement though, wish I had discovered it years ago

 

[woodieallen]

Having done a little bit of lime work, Adam, your posts are inspirational. Thank you.

 

[danst96]

I thought adding lime to cement mortar, usualy hydrated rather than hydraulic or fat lime, increased flexibility rather than strength.
I have always taken the view that the stuff between the bricks, or stone for that matter, was to keep them apart rather than stick them together.

Yes and as a result is less brittle and is generally considered fire resistant. It's often used in fire places. I built a brick pizza oven when I was still in school using a mix of lime and cement.

 

[chaoticbob]

Thanks for the info Adam - very relevant to me as well as I'm grappling with a 19th century house built of limestone (no DPC obviously) which needs to breath.

However, for the record:

...
Lime mortar has two sets, an initial set where it goes stiff quite quickly and a hydraulic set when it starts to absorb CO2 and turn into calcium carbonate. The initial set can be broken by smashing the mix with a lump hammer. Once you've done that it becomes plastic again and takes a while to set, as it's relying on the hydraulic set this time and that can take a month to harden or longer if it's cold.
...

isn't quite right. Hydraulic cements (eg Portland) are so named because they set by the hydration of complex silicates - it's the action of water which make them set. Lime mortar (which is calcium hydroxide) sets, as you say, by reacting with atmospheric carbon dioxide to form calcium carbonate. The water in lime putty is not chemically relevant. NHL's (Natural hydraulic limes) as I understand it are naturally occurring mixtures of silicates and lime which give a compromise between the fast-setting properties of cement and the flexibility/ breathability of pure lime. The 'hydraulic set' is the first phase where the silicates are hydrated, followed by the long wait for the lime to set. I think!
I'm not trying to undermine your advice, obviously the fruit of long experience, just being a bit sciency! I'd be interested to know if I'm wrong on this.
Bob

 

[pgrbff]

Thanks for the info Adam - very relevant to me as well as I'm grappling with a 19th century house built of limestone (no DPC obviously) which needs to breath.

However, for the record:


isn't quite right. Hydraulic cements (eg Portland) are so named because they set by the hydration of complex silicates - it's the action of water which make them set. Lime mortar (which is calcium hydroxide) sets, as you say, by reacting with atmospheric carbon dioxide to form calcium carbonate. The water in lime putty is not chemically relevant. NHL's (Natural hydraulic limes) as I understand it are naturally occurring mixtures of silicates and lime which give a compromise between the fast-setting properties of cement and the flexibility/ breathability of pure lime. The 'hydraulic set' is the first phase where the silicates are hydrated, followed by the long wait for the lime to set. I think!
I'm not trying to undermine your advice, obviously the fruit of long experience, just being a bit sciency! I'd be interested to know if I'm wrong on this.
Bob

I rebuilt an C18th farmhouse in very wet Ireland, limestone. All work carried out using fat lime mortars occasionally gauged with NHL3.5. No damp whatsover anywhere but I confess I deliberaty kept the house well ventilated. I would tend to agree.
Fat lime mortars can be knocked back up repeatedly, infact unless you have used them before you would think them unusable, esoecially with standard mixers. Before I found my rollerpan I would knock them up in a bucket with a pickaxe handle.
I would advise against re-working hydraulic based mortars after they start to set up, which can be suprisinly quick in warm weather. Having said that from a practical point of view it does happen and I confess to being guilty myself. I have no evidence, just lots of practice.

 

[johnnyb]

yes I thought nhl was initially made from a type of lime with pozzolans already present. no doubt its more controlled in these enlightened times. the hydraulicness of limes was first made formal during victorian times after failures in demanding exposed situations( lighthouses etc) although the Romans knew all about it.
by all accounts hydraulic limes have much less breathability than non hydraulic but would usually be used according to exposure. adding pozzolans during mixing and using non hydraulic lime seemed like a good compromise ( in my mind at least) .this allows you to use mature lime and still have a hydraulic set. in the 90s limelore was like secret knowledge but its much much more available now. its to late to be using lime seriously it was frosty yesterday here.

 

[pgrbff]

yes I thought nhl was initially made from a type of lime with pozzolans already present. no doubt its more controlled in these enlightened times. the hydraulicness of limes was first made formal during victorian times after failures in demanding exposed situations( lighthouses etc) although the Romans knew all about it.
by all accounts hydraulic limes have much less breathability than non hydraulic but would usually be used according to exposure. adding pozzolans during mixing and using non hydraulic lime seemed like a good compromise ( in my mind at least) .this allows you to use mature lime and still have a hydraulic set. in the 90s limelore was like secret knowledge but its much much more available now. its to late to be using lime seriously it was frosty yesterday here.

All of the premixed lime mortars you buy in Italy are so easy to use compared to fat lime mortars and mixing your own mortar using hydraulic lime and sand that I'm sure they mustadd all sorts of additives to them.