Many times, my past Henson Painting clients assumed that their mildew covered house needed to be painted. It was quite common to clean their homes and have them question whether painting the house was really needed. Removing mildew can be that dramatic. Mildew is also hard on painted surfaces and can lead to premature paint failure. There is a surprising amount of mildew on homes in the Sacramento region for such a dry climate. It can be very prevalent on the shady side of a home or under the eaves. Below is a picture of the mildew covered siding, eaves and gutters at my rental. Yes, yes, I have been a little lax in maintaining it. In my defense, it is in Arkansas and I live in Elk Grove, CA. It is quite a commute!
The Easy Fix
I sprayed the siding with a garden sprayer using a solution of one part bleach and four parts water. If the discoloration is mildew, then it will begin to fade away very quickly. Let the solution stay on the surface for ten minutes or so. If it looks like it worked, rinse the surface off with water. If the discoloration remains, spray the surface again with the bleach solution (maybe with a little stronger solution) and scrub the surface with a nylon scrub brush. Make sure to rinse off your plants and other vegetation when you are done. This is my siding after it was sprayed it with the bleach solution.
It requires very little work with great results. This siding did need to be sprayed twice, but I did not scrub it. The day was cold and I was a little bit on the lazy side. Still, a remarkable improvement.
A Note on Safety
You should wear safety glasses, gloves and long sleeves. I have done it without glasses and it is really hard on your eyes. Also, do not mix different chemicals together. Mixing chemicals can be very dangerous. (See Dunn Edward link below)
I have used all kinds of sprayers, including the type you can carry on your back. If you will be on ladders, the one you carry on your back makes a lot of sense. It frees your hands to hold onto the ladder. They are more expensive, though, so I use a small capacity sprayer. I think it holds 1.5 gallons of solution or so.
Are you selling a home with discolored exterior surfaces? Maybe all you need to do is clean it. Give me a call if you need a little help. Other tips to get your home ready to sell.