Spray Plaster

Has anyone ever used a hopper or an industrial spray-gun to apply plaster on their bale walls?

A couple videos on youtube have shown it in action. Looks neat. Seems to work fine with clay or lime-based plasters. I'm exploring the idea of applying it to the walls of my own recently built strawbale home.

I notice hoppers for sale on alibaba.com for like, $70USD. Might this be a worthy investment? I believe I would need a generator and an air compressor to make it work. Would save a hell of a lot of time, I reckon.

What do you think?

At the natural building workshop I attended, we used a texture sprayer to apply clay slip to the straw bales. It worked very well. It required electricity.

Anyone know more about the technical details of the sprayer equipment and required compressor power? Seems like a pretty big time saver especially if warm bodies are in short supply..

Standard texture spray guns want air pressure in the range of 60-90 psi for spraying clay slips or lime base earthen plasters because of the density of the material.

You will want a compressor with at least a 20 gal. reserve tank for the air so you don't have to stop and wait for pressure build up many, many times during the spraying.
(I have used 80 gal. tank two stage, 5 hp., 230v compressors for plaster spraying and I have also used 6 gal. pancake compressors, believe me, the more air available the happier you will be with the end results).

Any time you stop spraying plasters (as in you ran out of air supply due to too small a tank) you need to watch the consistency in the hopper or you might end up with a clogged gun and that means stopping to clean out the gun then put is all back together and starting again.

Great, thanks.

My compressor is about as beefy as can run on 15a/120v, and has a 20gal tank.. certainly not up to the standard of that 5hp unit, but still sounds like I'll be in pretty good shape once I get around to plumbing in a second tank, especially if I borrow a smaller compressor to add a bit more oomph.

Yep I think you will be good with a setup like that.  A second compressor will lower the recovery time.

Damien Vallero wrote:Has anyone ever used a hopper or an industrial spray-gun to apply plaster on their bale walls?

A couple videos on youtube have shown it in action. Looks neat. Seems to work fine with clay or lime-based plasters. I'm exploring the idea of applying it to the walls of my own recently built strawbale home.

I notice hoppers for sale on alibaba.com for like, $70USD. Might this be a worthy investment? I believe I would need a generator and an air compressor to make it work. Would save a hell of a lot of time, I reckon.

What do you think?

Hi Damien! I found this old thread while searching and wanted to reach out and see how your project went. Did you end up spraying your bales with slip? I am building a strawbale house right now, and will begin plastering within the next couple of weeks. I'm trying to calculate how much clay I'll need (I have to truck it in, we bought the side of a mountain and we have lots of rock here, but no site clay!). Do you have a sense of what volume of clay or slip you used to cover what square footage? Any lessons learned or tips you could share? Thanks!

Hi Andrea,

The above post was Damien’s last post. He has not been active for a few years.

Bryant RedHawk wrote:Standard texture spray guns want air pressure in the range of 60-90 psi for spraying clay slips or lime base earthen plasters because of the density of the material.

You will want a compressor with at least a 20 gal. reserve tank for the air so you don't have to stop and wait for pressure build up many, many times during the spraying.
(I have used 80 gal. tank two stage, 5 hp., 230v compressors for plaster spraying and I have also used 6 gal. pancake compressors, believe me, the more air available the happier you will be with the end results).

Any time you stop spraying plasters (as in you ran out of air supply due to too small a tank) you need to watch the consistency in the hopper or you might end up with a clogged gun and that means stopping to clean out the gun then put is all back together and starting again.

I currently use a 6 HP gas "wheelbarrow" compressor and hopper guns to spray papercrete and EPIC (papercrete combined with EPS beads) For continuous spraying I find the horsepower to be way more important than the tank capacity. Anything less than 5 HP (gasoline) or 2 HP electric is very slow going. You can rent gas powered air compressors for about $100/day, that is usually what I recommend.