1 50# bag of hydrated lime, according to these figures, can cover 45 square feet of wall with a finished thickness of 5/8". This seems to be pretty accurate based on past experience using this.

Hi DL

Recheck some numbers. At 3/4", 16 sq ft of coverage per cubic ft or a total of 35 cu. ft. of mortar for the project.

DL

After reading the postings on this subject, I offer the following to further cloud the picture. If you find that this is too much information ......... I apologize ahead of time. I have found that when a health department requires wall surfaces to be easily cleaned they mean that it should be smooth enough to be wiped down like a hard tile surface. I don't think the lime washed, sand float finish you are contemplating will give you that but a smooth, hard-troweled finish will.

Wood lath over studs spaced at 24" o.c. should probably be no less than 3/8" thick with a 1/4" - 3/8" gap, depending upon the size of your aggregate and the type of fiber that is in the base/scratch coat. For a lime scratch coat that would most likely be hair, hemp or even chopped straw.

I would not recommend that you use a clay based scratch coat in your plaster system. To get the best bond possible between the lime finish and the clay base requires several layers of plaster of different combinations with the clay and lime. Probably more work than the overall job warrants. I'd suggest you consider a 3-coat lime plaster with an overall thickness of 5/8" - 3/4".

Plaster work is a little different than mortar work in that the hydrated lime actually needs to be mixed with water (lime into water) and soaked for a length of time to allow it to full absorb all of the water it can. Allow it to soak in a covered container from 1 to 3 weeks. During this time the lime particles will settle to the bottom and form a putty with a consistency that approaches cream cheese. As long as you keep the putty away from air and under water it will last indefinitely. Lime putty, like wine, gets better with age. A 50 lb. bag of hydrated lime mixed with about 10 gallons of water will yield about 8 gallons of lime putty. Those 8 gallons of putty can be used in the following mixes.

Scratch Coat - 50 sf of coverage @ 3/8" - 1/2" thickness mixed at a ratio of 1 part lime putty to 2 - 2 1/2 parts aggregate and fiber added.
Brown Coat - 62 sf of coverage @ 3/8" thickness mixed at a ratio of 1:1.75 - 2
Finish Coat - 180 sf of coverage @ 1/8" thickness mixed at a ratio of 1:1 - 1.5

Aggregate gradation is based upon the thickness of the plaster coat that is being prepared. If your project will not allow the time needed for the lime to properly carbonize and cure out then gauging it with white cement is always an option.

The information here is based upon my work with both clay and lime plasters that I am called upon to provide from time to time. I hope it is helpful.

thanks, great info

the sand float won't be the topcoat. I do that on the middle coat because I found that it effectively removes any wave that may have formed, making the top coat that much easier to apply.

And I do know about soaking it too. It is not actually 100% necessary, but it is definitely worth it. The lime will work if you just mix it straight into the sand with water, but won't work as well.

Thanks for the info about clay too.

But what I was considering is more or less a clay undercoat, an outer coat with a little lime mixed in for hardness, a a limewash or whitewash finish. So it would technically be a clay wall altogether.

will there be insulation in the wall? I've been wondering how the moisture/vapor barrier issues with more conventional insulation batt or cellulose with lime or clay wall finishes. I understand (or think so) the mediating affects of these finishes, but it has been more in the context of some other clay based interior wall system/ insulation. In addition, vapor not being good for these breathable systems. any light
Brandon

the hydrated lime you speak of, is this a NHL grade, or just standard construction grade hydrated lime?
Brandon

DL

Sounds like you've got a good plan. Just to be safe though .......... I'd prepare a sample of the wall plaster with the finish you plan to use and show it to a health inspector for their approval before getting too far along with the room.

Heavy

I believe DL is referring to standard Type 'S' hydrated lime.

Yes, Type 'S' lime, manufactured and sold as a mortar reinforcer, but what it really is is partially slaked quicklime.

As far as health inspection...

In the good old State of Indiana, regulations are wonderfully loose. And Howard county inspection is all but non existent.
For example, recently in the nearby city of Kokomo we fixed up a small stand that is used as one of those drive through drink deals (drive through diabetes). It was built up on a parking lot, and so had no way of handling drainage very well. So as a result, the bottom was rotting away. So inside the bottoms of the studs and sheathing were full of rot fungus, and the bottom 2 feet of wall was colonized with good old black mold (yum).

Most places in the US would have declared this place unfit, and destroyed it. But good old Indiana laid-back policy means we could repair it instead. So the solution? We replaced the entire bottom 3 feet or so of the structure. When the city inspector came by, who is both building and health inspector, we more or less told him what we did and he said it was good. He's a great guy, we needed to move a gigantic ice machine out of our way, so he took me down underneath the city building to pick up a tool do lift and move very heavy things.

But that said, I still do want to make things to meet and exceed the standards.

The cheese that is being processed is whey cultured and raw milk. While there are no explicitly stricter requirements regarding sanitation for this I want to have a very sanitary environment for the purposes of quality control.
Cheese is cultured by bacteria, yeast, and molds. They will define its flavor. If unwanted bacteria gets into the mix, it may not be harmful to your health but it will harm the quality of your cheese.
Furthermore, my culturing method is to follow the traditional practice of holding over whey from the previous batch to introduce bacteria into the next batch. This means that if a batch is ruined by contamination, so is my culture. So you see how very important sanitation is. This method is a lot riskier than using packaged starter cultures, but it results in a richer, better and more complex cheese.

Also,

We will be aging and maturing our cheese in an unsealed basement, because the humidity and temperature are consistent year round, and are right on where they need to be (quite a bit like a natural cave, which is the ideal environment)

But for sanitation reasons, I want to coat over the 100+ year old exposed concrete blocks with a thin coat of lime plaster, to inhibit mold and make it easy to wash.

What would you suggest for this, Bruce? (and others)

would a single brown coat with a light skim coat suffice?

And also, the firebox for our vat will be built of small field stones (random round here in Central IN) mortared with lime-reinforced mud (with some chopped straw). How much lime would you recommend adding? It does not have to be waterproof, it will be inside.

Recapping, here is my plans as of now (for review)

For the shop walls: Base coat of clay mixed with chopped straw, covered with a coat of lime-reinforced clay, finished with a plaster skim and limewash. Possibly at some point I might have a tinted plaster and do some simple sgraffito work as well. I like sgraffito.

For the basement walls: Brow coat with skim coat

Firebox: random round field stone with lime and straw reinforced mortar.