Water, it is such an interesting force; it can be gentle and serene or create absolute destruction because it finds its way where it should not be. Aside from the possible ill-effects that an unresolved leak can create, like mould, there is no point in coating water stains if the problem persists because the staining will keep occurring. Not to mention the substrate may become permanently damaged resulting in further repairs than anticipated. Depending on where the staining is happening, it can guide you to where the moisture is entering. For instance, if it happens near windows or doors, it may be a caulking issue; seeing stains coming through the ceiling likely means water could be coming in through a vent or an area that has become unsealed. Most brands of paint have their own bathroom specific paint as condensation can also be a culprit of water staining, although this is not as intrusive as water damage but can still make the aesthetic of the are off-putting.
I have personally had the ceiling over my bathtub fall in because the person in the apartment above me put a bucket under their tub faucet and somehow fed too much into the overflow tube. If you look at the first photo, you can see it was starting to crack, and I called my landlord at the time who said they would come to check it out. Knowing it was going to be a little while before he arrived, I went to grab a coffee; I was back within half an hour and I came home to the ceiling in my tub. Then they said they fixed it, well, as you can see on the newly installed drywall, it was not resolved. At this point, I was moving out anyway and washed my hands of the whole deal. I am grateful the debris and water were contained to my tub and since I was renting, I was not the one paying for the repairs. Problems like these can be a large source of frustration, even more so when it comes out of your pocket.
Of course, drywall is not the only surface that needs protecting, coating concrete is done for various purposes such as protection from general wear and tear, moisture, dust and dirt, heavy traffic, as well as chemicals. When it comes to coating concrete surfaces, it needs to properly outgas otherwise you can end up with pinholes, cured bubbles, or lumps. As concrete is porous, it has a web of tiny air pockets and cracks that can allow moisture, air and contaminants to become trapped even after it has cured. This allows moisture and air to travel in and out; and while it does not always cause the above-mentioned flaws, they are more likely to happen during summer months due to the fluctuations in temperature of air and substrates that can occur in a day. Outgassing can even occur long after the concrete has cured.
The reason you get pinholes or blistering is that vapour has become trapped under an unbreathable coating. To help prevent out-gassing, make sure the concrete temperature is at least if not warmer than the air temperature when applying the coating; if your project allows for it, you can pre-heat your slab by indirect heat or increasing the air temperature to bring the concrete up to ambient conditions, then shutting off the heat and allowing the air to cool before coating your slab. However, it is not the only temperature that can create issues with outgassing but also barometric pressure causing air to move in and out of the concrete.
Now we have talked about surfaces, substrates, and water, but what about products and water? Generally speaking, they do not mix as excess moisture or humidity impedes the curing process of most coatings. However, there are some specialty products out there like Sherwin Williams Amorseal Rexthane and Corothane Pre-Prime, which are moisture cure urethanes. You read that right, humidity helps it dry – crazy, right?
Amerlock 2 is also an incredible product, it is even rated for secondary containment which means, that if a complete seal has been created, the product essentially becomes a bladder.
The final nightmare occurrence we are going to cover is hydrostatic pressure, which is the pressure exerted by the water onto a surface from a specific height which increases in proportion to depth measured from the ground surface because of the increasing weight of fluid exerting downward force from above due to gravity.
This occurrence can create blistering, like outgassing with concrete, but occurs due to high water tables, excessive stormwater run-off, or just poor drainage in general. A general rule of thumb, if the moisture content of masonry is above 15%, it must dry out before it is suitable to be coated.
Overall, with the exception of a few very specialized products, the atmosphere and substrate need to be within a certain moisture range for your coating to adhere and cure properly, otherwise it is going to fail. Also, if you do not resolve a leak, you will have a much larger issue than just some unsightly water marks which can result in costly and time-consuming repairs. Until next time.
