Change Management Consultant
The views stated in my posts are my personal views and not that of any other organisation.
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timmmay: Thanks SXZ, that's useful. I read the property act 2007 this morning, I'd rather not get a court order, that's not the way to make friendly neighbors, but good to know it's possible.
I've been put onto a product called "Sto Protect", which is a clear silicone coating that will apparently do the job. It's around $280 direct from them in a 15L pail, and anyone can apply it. I'm going to suggest that if he wants the mural protected he can pay for the product and the time of the painter to apply it, or alternately I'll pay to have it properly wateproofed. There will be a caveat that if it leaks after applying this product I'll have to have it done properly.
BruceHamilton: Just a quick note. Most deep-penetrating ( as opposed to surface membranes/film silicones ) intended for water barriers require the concrete to be clean and very dry, as the silicone is dissolved in a very thin solvent ( or used neat - but that has safety issues ) to penetrate and react with residual water on the stone or slowly with air moisture. They will work well from the outside, but are far less effective from the inside. If the wall has steel reinforcing through the blocks, then external water will cause corrosion/metal expansion/cracking.
I highly recommend protecting from outside in. It's possible there are heavy water-repellent translucent films that could be applied based on silicones or fluoropolymers ( expensive ). You need to talk to specialist firms, as paint companies are unlikely to know much. Another alternative is clear, rigid, UV-resistant, plastic sheets bolted to wall.
Timmays first product he mentioned was as you say, requires direct application to concrete, removing any paint, etc, but the second was a protector that goes over the top. I did see that its not waterproof (cannot be used on horizontal surfaces) but that it allows run off, so hopefully it will be fine.
timmmay: The manufacturer told me it was fine, though I may run the data sheet past the neighbor just to be safe.
timmmay: Yeah might as well.
trig42: Tell him either you fix it, or it comes down? Both ways he loses the mural painted on YOUR shed.