How to make a concrete block wall air tight?

Hi I am currently extending my studio by adding another tracking room. The Outer leaf walls of my room within a room proposed construction are 4" solid concrete blocks and they are definitely not air tight. Previously in another tracking room @ the studio I had an identical wall and to achieve air tightness i rendered the wall with a plaster skim coat. This was very effective but a lot of work... My question is are there any other ways to seal these blocks airtight that doesn't involve rendering/ plastering (I'm getting lazy as i get older :) ) Is it sufficient to patch up any visible cracks or holes in the blocks and joints and hope for the best? Any advise much appreciated regards hally

Good to see you back again, Hally! :thu: Concrete is porous. The surface has hundreds of tiny "holes" or "pores" for every square inch, and air can penetrate quite deeply into those. As can moisture (humidity and also water). That messes up your isolation, and also can potentially create a problem for "damp", fungus, mold. What you did last time, rendering the surface, is indeed the best way to deal with that. Second best is to just seal the surface with a good quality masonry sealant. Of course, the wall itself needs to be in good condition for that to work, with all of the mortar in good shape, no cracks, not flaky, not loose, dry, etc. If the wall is fairly new (recently completed, in the last couple of years), and was built well by good bricklayers, then that might be an option. But if the wall is older, or not in good shape, or was not built well, then I'd really suggest plastering again, like you did last time. If you aren't up to it yourself, then you could hire someone to do it for you. You might even find that, among your musician friends, there are people who know how to do that, and would trade their time and skills for future free recording time in your studio... - Stuart -

Hi Stuart, Thanks for the response... I don't know why i wasn't notified of this in my email, anyway I sucked it up and got on with the plastering, i forgot how relaxing and therapeutic plastering is :D I think I'll start a build diary of the process in a new thread https://drive.google.com/file/d/1n3fNmQ ... sp=sharing https://drive.google.com/file/d/1-urWAt ... sp=sharing https://drive.google.com/file/d/1bTbzbX ... sp=sharing