When I did my test spots one was with onerestore and one was with a strong house wash mix both worked great but the cost of the house wash mix is far less, now that being said I clean a lot of brick and I use eaco chem products everyday and they have great products and they will answer any questions you will have.With a building that large you need to do some test spots the church that I did was right on the square in town and I had to becareful too,if you have any questions give me a call I'd be glad to give you my 2 cents.