Updated 10/11/23:  Here is some of my research and we are looking for advice on mixes for lime plaster and mortar for foundations, floors, and structural repairs. Hope to update with more info.

We are currently building a multi-use 10′ x 20′ (interior dimensions) shed with 2″ x 6″ framing on a rubble foundation, with about 3/4″ of the studs showing inside so we can attach pegboards and shelving for mushroom and hydro salad grows.

Why use lime?

An excellent primer by the Ludlow Civic Society explains lime, quicklime, lime mortar, hydrated lime and hydraulic lime along with slaking a bit of quicklime into putty.

Here is Kris Harbour slaking a ton of quicklime:

Don’t miss the comments on the video!

I was inspired and am going try to slake my first ton in 230 g or so containers we previously used for gravity watering.  I use a different setup for irrigation now, cut the top off the first tank and cleaned it.   Have to go slow to not melt it!

We also set up so the wind will blow dust away from people.

Nigel Copsey Demo Hot Lime Moffat June 2021

48 min — very interesting, Nigel has so much to say!  Whitewash and mortar.

2 hours 48 min  — All things lime!

Nigel is an amazing activist, calling out the industry as the liars they are.

Some notes:

(Very incomplete, took notes while I watched and hope to update on a slow day)

Airlime for good bond, ideally pure lime with no additives.

Nigel is no fan of NHL and explains in great detail how industry marketing has nothing to do with reality. In lab tests both the softest and the hardest NHL was NHL 3.5.

Gain in strength results in loss of capillarity and hardness is not predictable.  Requires lots of hydration, has no water retentivity and makes poor bond.

Cement expands and contracts, destroying the bond until it falls off and causes wet buildings.

Nigel explains that capillarity comes from airlime content.  Hot mix.   Putty for finish coats.   Never use linseed oil to waterproof lime, as it will trap moisture in the walls and subsequent coats will not stick.

Shrinkage:  NHL and cement expand a little when wet, don’t breathe, are too hard.

Earth lime mortar has been extensively used in France.

Chinese mortar:  70% earth and 30% lime, used on most of Great Wall.

Earth mortar [around 50:00]  Demo of earth mix with Binder Loam. Shouldn’t have more than 20% clay.  Earth lime construction was dominant in the Roman Empire and all over the world.  Clay also expands and shrinks as it gets wet and dries.

Hair (cows), hay (not straw) in Yorkshire — to resist cracking.

1:19 min:   course sand, fine sand, …    One lime to three.   When using putty, it contains water and therefore not enough lime.

Quicklime:  Historically, add water to quicklime, NOW: add quicklime to water.

The longer quicklime slaked, the weaker the lime.  1 – 2 weeks max.

1 volume quicklime to 2 volume

1:52 min:  Lime “paste”

Modern quicklime is fired at hire temps, making it more reactive and more shrinkage.  Traditionally fired at 900 degrees.

(Have to watch it again and check and expand on my notes, it’s a long video!)

Here’s what happens when you’re not careful slaking quicklime:

Thanks for sharing!

Philonema Paul’s red brick dust hot mixing recipe: