If it ain't broke
Every day, in our little home inspection business, I spend half my day telling people about things they need to get fixed. I spend the other half telling people that some things that they think need fixing don't need anything at all. A few examples follow. I'll just start at the top of the house, and work my way down.
In our part of the world, algae grows on roof shingles. It's growing on my roof right now, just like it has for the last 10 years. The algae does not hurt anything. It just makes streaks on the roof. People don't like the streaks because they think it makes their roof look dirty.
So, don't you know, there are products and services aplenty to get rid of those pesky streaks. The usual "cure" for streaky shingles is power washing. Power washing involves a noisy air compressor and a high-pressure hose, which directs a high-speed stream of water and chemicals onto your roof. Power washing will blast the streaks off your roof. Problem is, it's likely to blast the mineral coating off the shingles, too. If you want to age your roof about 5 - 10 years in one day, power washing is a great way to do it. I don't recommend power washing. Heck, even if it worked, the algae would start growing back the next day.
If you ask me, an algae-streaked roof doesn't need anything. I say just leave it alone. When the existing shingles wear out, just install new shingles that have algae inhibitors built in.
Old wood siding and windows
A few decades back, some marketing genius came up with the notion of "maintenance-free" exteriors. I can imagine his pitch to his board of directors:"Here's what we'll do: We'll tell people they'll never have to paint again. We'll tell 'em they can just cover up all the wood on their house with paper-thin aluminum and cheap plastic crap. We'll sell the stuff by the trainload!"
He was right. The never-paint-again scheme worked, and continues to work today. There are still people who haven't done the math, and haven't figured out that painting a house every 10 years or so is cheaper than wrapping it up in materials that are just a little sturdier than duct tape.
The fake-siding business was so good that it morphed into the cheapass-window business. These days, when a perfectly good, old wood window gets a little wear and tear, a whole lot of people don't even think about patching it up, repainting it and weatherstripping it. Nope, they rip out a wood window that would cost $500 to build today, and replace it with a $100 plastic trailer window.
You fake-siding-and-replacement-window believers, listen to me: When it comes to the outside parts of your house, wood is going to work better than aluminum or vinyl. If wood has a little rot in it, you can fix that with epoxy. If some old paint is peeling, you can scrape that off, then repaint. If a window is drafty, or doesn't open and close easily, you can fix that with a scraper, some weatherstripping and a little low-skill manual labor. Finally, consider the resale value of your house. It will almost surely be higher if you don't cover up the original materials.
At least once a week, somebody will look at the brick veneer on the outside of his house, and notice a pattern of holes in the mortar, just above the foundation. Then he'll ask me how to patch the holes.
Well, those are weep holes. They're supposed to be there. They're supposed to have flashing behind them, to catch water that leaks through the brick, and dump it outside. So far, I've yet to find a local house that has the flashing. Even so, it's better to have unflashed weep holes than no weep holes at all.
Weep holes don't need patching. Leave them alone.
Fences and bushes around the heat-and-air equipment
Some people try to hide their heat-and-air equipment. They build little fences, or plant bushes around the furnaces and air-conditioning units. I don't know why.
Here's the problem: One day, somebody is going to have to work on the heat-and-air equipment. He's going to need enough room to squat, kneel, and crawl beside the equipment. He's going to need enough room for his toolbox, and maybe a tank of refrigerant. If you just have to build something, build it at least 30 inches away from heat-and-air stuff. Better yet, save yourself some money and hassle, and don't put your heat-and-air equipment in a corral.
Sealing the driveway
The same folks who try to conceal their heaters just love to seal their aggregate driveways. Well, your driveway is not a tabletop. It does not need to be shiny, and it does not need to be sealed.
While I'm thinking about it: There is no reason to spend extra money on an aggregate driveway. They're slick when they're wet, and they'll hurt your feet if you walk on them barefooted. Just use regular old concrete for your driveway. It's cheaper, and works better.