Can a Chimney be Painted with House Paint?

No, the paint will trap moisture in the bricks.  Bricks can hold up to 35% of their mass. Older bricks are on the higher side more modern bricks are on the lower side of the scale. But still, even 7% water is amazing.  Paint is impermeable, you may think that would be a good thing to keep water out, but since bricks start absorbing water from the first day they are placed, painting them is just keeping the water in. Trapping water in brick is ok until the weather gets cold. The freezing and thawing can cause them to spall or crack. With more water entering and none escaping, a painted brick will deteriorate at a much faster rate than an unpainted one. Yes, an unpainted brick still suffers from the freeze-thaw cycle, but the key to giving your exterior brick a longer life is limiting the water that saturates bricks, while still allowing water vapor to get out. If you are painting them to seal them a much better alternative would be a vapor-permeable sealant that helps keep water out but allow vapor to escape.

If you want your bricks to be a different color, you can stain bricks to change their color. They now have stains available to do this, and still, allow you to waterproof with a sealant made for chimneys. If you limit water going in while allowing water vapor to go out, your chimney can last you a lifetime. If you have bricks that are already painted removing it will be quite a challenge, but it can be done using a combination of patience and chemical strippers. If you get too aggressive with removing paint from a chimney, you could very well do more harm than good. Many chimneys are painted so that a new home buyer won’t notice the terrible condition of a chimney. Some chimneys may have been fine when they were first painted, but now several layers of paint are hiding extremely weak, crumbly masonry that has been saturated over the years. As you peel back a layer of paint, you may find the brick’s face comes with it. If you attempt pressure washing or wire brushing the chimney, you may end up with a pile of bricks on your roof. If this happens you may be looking at rebuilding your chimney. It is always best to consult with a professional before attempting to remove any paint from your chimney.