Hello! I'm new to all of this. I don't know any of the abbreviations, so please bare with me. I'm attempting to build a silo house/guest house in a residential area. Although I'm not in a subdivision or historic district, the zoning board is giving me a terribly hard time to get a permit. They want me to make the outside walls of the silo flat and even with no grooves. I'm trying to find a material to fill in the grooves and keep it as green and cost efficient as possible. I've explored, putty, mortar, all kinds of ideas, but I need something that will stick to the galvanized steel and allow me to smooth it and paint over it. I don't know what to do! If I don't get a permit in soon with a viable plan, they are going to make me take the silo down. That in and of itself will be a nightmare. If anyone has any thoughts or knowledge I would greatly appreciate it!!! I need help badly.

Poorly written. I think you have a silo structure with galvanized steel on the exterior, right. I might be a genius, but why don't you remove the steel and save a lot of trouble?

Nothing comes to mind but good luck....

I'm going to give you the way I would do it, since I like doing less labor. I would put 2 layers of 1/4 " OSB over the metal. It bends easily and should give you a good base for whatever you choose over it . I would glue the 2 layers together upon install.

Wrap it with stucco lath, attach with self drilling sheet metal screws & washers, then apply portland cement based stucco.

Here are some examples:

https://www.clarkdietrich.com/products/metal-lath/diamond-mesh-lath

https://www.lowes.com/pd/QUIKRETE-One-Coat-80-lb-Premixed-Finish-Coat-Stucco-Mix/3034358

You could look into wrapping it in metal mesh and spraying it down with aircrete.  When dealing with code just refer to it as "Cement Parging".  Don't talk about the aircrete part unless they ask you a direct question.  If you have a local pool builder who works with gunite or shotcrete, go talk to them.

Thanks for the thread. My friend was looking for related information.