Hi Just joined this thread due to looking for something else. When I look at your pic and how old the place is then read an architect has specified K11 then someone else using it on other farm buildings that will now be ruined, I despair. In a nutshell I am a chartered builder and work in conservation carrying out historic survey and consultancy advice. Ben recorded a podcast a short while ago and explains everything about what you have and how it will work without any K11 or anything else that is sold by chemical companies. Please have a listen then make you mind up. Thanks
https://www.buildingsustainabilitypodcast.com/guests/ben-kerslake/