Does anyone out there have a good figure for coverage of lime plaster?

Specifically, how much square footage of wall could I cover with 50 lbs of hydrated lime (powder) at 1/2" and 3/4" thicknesses?

Hello DL

You know you have a very good question but being one that has wrestled with such questions in the past I will try and give you some guidance

The old text books give you formulas and coverage guides for slacked lime mixtures but unfortunately I do not have one of these texts at hand so in that regard I suggest the following:

Mix up a weighed batch of say5 lbs, and then on a flat surface apply it and you will have a close evaluaion of the coverage

You should build up the layers in stages to reach the finished thickness, putting on a base or rough coat , then a scratch coat, and then the finished coat

I suspect that you are mixing in some sand if it is a base mixture or rough coat, but if it is a finish coat then you will just be applying a lime only mixture

I personally don't not know how well hydrated lime will work so you will have to experiment

At UCV we did use hydrated lime, sand mixture to lay a stone foundation for a smoke house, and it seemed to work well

I do suggest using a very small amount of white portland cement just to ensure the proper hardness of the finished surface, there again I suggest some experimentation is in order, do not overdo this step but use caution.

hope this helps

NH

NH,

I have used it before. But just on repairs on our house. I never really bothered to measure the coverage. I also used it to make a bread oven, made of dry stacked bricks and sealed with plaster.

So I am aware of the need to build it up in layers.

But here I am making a room of certain dimensions, and for figuring costs I need to know how much plaster it will take to cover the walls and ceiling.

My plan is to have a base coat, at least one build coat with the final build coat given a wet sponge rub to make it even -this also gives it a grainy texture. It will then be finished with a lime wash to make it smooth, because this will be a comercial cheesemaking room and Indiana law requires that such facilities have smooth walls that are easily cleaned. I chose to go with lime plaster for its antibacterial properties.

I will try a test patch to estimate coverage, that is a good idea. I have some old plaster I can use. Hydrated lime works well, provided you use it quickly. It will break down over time once exposed to air and no longer make good plaster.

For Hydrated lime, I use a 3:1 ratio of sand to lime, mixed on a board with a shovel.

Have you seen/read "using natural finishes" by weismann and bryce. I've read a bit lately, and particularly like this one. Its borrowed, but worth buying. What you applying it over. I been increasingly interested in this lime and earth plasters, since with used clay finish on our walls in an addition. the book mentions:@ lime aggregate coverage- scratch 5gal. to 2.5msq thickness 10mm; straight coat-5gal. to 4msq at 6mm thick; finish 5gal. to 6msq at 3mm thick.

Brandon

The frame will be 2' OC studs (it will support no structural loads) with lath on the inside. The plaster will probably go directly on this lath, but I may have a clay base with a plaster finish instead (a lot cheaper to do myself, even if it does take more work) This mostly depends on whether or not I can dig up suitable loam nearby.

also, I have plenty of manure available, and may use such a mixture for the undercoat. BUT since this is to be a commercial cheese operation, I doubt I will go down that road...

Mortar volume equals sand volume.

An ideal mortar mix has a lime volume equal to the space between the grains of sand, so to meassure the space, place a known volume of dry sand in a bucket and add meassured water until the water level reaches the top of the sand. Then calculate sand to lime ratio.

Calculate area of walls to be plastered then multiply by thickness of plaster equals volume of mortar. Apply a fudge factor to avoid shortfall. Plaster volume equals sand volume. Apply sand/lime ratio for amount of lime needed.

To account for squeeze through and formation of the keys add at least 1/8" over plaster layer thickness.

Through a lot of figuring and searching, and with the suggestions made for figuring, I have figured that to cover 560 square feet, I need about 63 cubic feet of plaster, so about 21 cubic feet of lime...
then figuring based on a figure I found for 30 pounds per cubic foot of hydrated lime, I figured I will need 620 pounds of lime, which comes in 50 pound bags so I need to buy 13 bags of lime. By Roger's suggestion, this will yield a plaster thickness of about 5/8" (I used 3/4" for my figures)

And if I go with a clay wall with a plaster finish, then I will only need 4 bags of lime