That established, how to do it? There are two schools of thought about cleaning siding:
- Pressure Washer: Purchase or rent a power washer and spray it down thoroughly. Pros: Less manual labor. Cons: Siding damage, water injected under siding, or dirt remaining on house. There are ways to safely clean your house before painting using a pressure washer, including using lower psi pressure washers, widening the spray, and standing at least two feet back.
- By Hand: Purchase cheap brushes and an even cheaper powdered cleaning solution. Scrub by hand. Pros: You'll have very clean, undamaged siding. Cons: It's the hardest form of manual labor.
Why Wash Anyway?Washing down your house exterior is just one part of preparing to paint your house. You would not expect for your new paint to attempt to stick to crumbly, flaky, failing paint; it just doesn't work. In the same sense, when a fresh coat of paint tries to stick to dirty siding, it too will fail. The problem is that it doesn't happen right away.
Paint applied to dirty siding will adhere in the short-term. But over the years, your house will experience paint failure.
I feel like I have fairly clean house siding. So, as an experiment, I went up 15 feet on an extension ladder and rubbed my hand once down the siding. Keep in mind that because this is high, it's less likely to become dirty from mud-spattering along the bottom edges and from normal touching from people and animals. Even so, my hand was dark-gray with a layer of fine soot. I live in a suburb of a metro area that has little, if any, smog. Imagine if you live in a city. Even if you're in the country, dust will build up on the siding.
Tools For Cleaning SidingWhy no pressure washer? If you use enough force to blast away all of the dirt, you stand a good chance of etching your siding. Yet if you hold the nozzle farther back, it's not enough to remove all of the dirt.
Yes, a pressure washer held at this distance will probably give you a "good enough" result to begin painting. Manual house-siding cleaning for getting the house perfectly clean.
- TSP: Tri-sodium phosphate is one of those great little secrets hiding in your hardware store. It's a powder (though can be found liquified, too) and is cheap. Mix half a cup with two gallons of warm water to make an all-purpose cleaning solution that leaves no film. See this video about removing stains from walls for more about TSP. Get a big 5 lb box.
- Hand Brush: A stiff-bristle hand brush roughly 9' long. Compare Prices - Siding Brush
- Long Brush: You need to be able to reach an extra 3 or 4 feet. Your hand brush might have a place to screw in a broom handle. If so, you can use this. To avoid continually dipping the brush into water, you can use a siding and eaves brush that runs water through the handle up to the brush. Compare Prices - Siding and Eaves Brush. One downside: it gets heavy after awhile.
- Garden Hose: An ordinary hose and nozzle.
- Wire Brush: Helps to brush away stuck-on mud and remnants of long-dead wasps' nests.
How to Clean Your SidingNow that you have your tools together, pick a warm, sunny day and begin cleaning. Remember to work from the top-down.
- Choose one side of the house as your cleaning project of the day and stick with it. It helps to mentally cordon that side into half or thirds, as an entire side of the house is too much to clean at once.
- With the siding dry, remove large pieces of debris with the wire brush, broom, and even a shop vacuum: dried mud, spiderwebs, bird nests, vacated wasp nests, etc.
- Gently spray one section of the siding with the garden hose. Caution: do not spray upward under siding or into air vents near the eaves which permit air circulation into the attic. In general, be aware of any place that may allow water to intrude under the siding or into the house. Also look for dryer and bathroom vents and around poorly-fitting windows.
- Scrub down the section with prepared TSP-water solution.
- Rinse off the section with clean water.
- Think it's already clean? Try mixing up fresh TSP-water solution again and re-scrubbing it. You'll be surprised at how dirty this second batch of water is.
- Move on to the next section below that one.
- When all sections are done, spray the entire house side once again.
- Let dry by itself at least 24-48 hours before painting.