On a recent tour with a potential buyer, agent Terri Vellios of Keller Williams Realty in Campbell, California, showed a $1.3 million house that had an addition to the original building.

The addition created an atrium in the middle of the house, with the bedrooms facing it. But none of the bedrooms could actually access the atrium; the only way into and out of it was through the sliding glass doors in the dining room.

About the same time, Gay Ashley of the Ashley Realty Group in Fairfax, Virgina, showed a house in which the sellers expanded their living space by turning a one-car garage into a bedroom and very small family room. But their contractor neglected to plan for heating and air conditioning. Consequently, the two spaces were extremely cramped, and only comfortable for a few months of the year.

Welcome to the real world of home "unimprovements" -- the part of the house makeover business that they fail to show on HGTV, the DIY network or even on "This Old House." The part in which changes to a house detract from its value rather than adding to it.

Every real estate professional has seen these miscues: everything from botched paint jobs obviously undertaken by Picassos who made no attempt to prepare the surface and dripped paint on the carpet, to building an addition around a huge oak tree.

Bad paint jobs can be corrected rather easily. But other mistakes, such as banging such long nails into a ceiling that they penetrate through the roof, are costly.

Former home inspector Glen Fisher once posted a photo on real estate site ActiveRain of nails protruding through a newly replaced roof. The homeowner's idea was sound: Put up a ceiling in the attic to create more living space. But the execution was poor: a calamity that led to hundreds of small leaks and required another entirely new roof.

"As a home inspector, I am continually amazed at what I observe," said Fisher. "Just when you believe you have seen it all, another property will show the worst results from a well-intentioned homeowner."

Take a house listed recently by Jan Green of RE/MAX Excalibur in Scottsdale, Arizona. The kitchen had been remodeled beautifully with a very expensive refrigerator, wine closet, double oven, cabinets and granite countertops. But the owner left the 20-year-old tile on the floor, and "every person who came through commented about how the old tile detracted from the gorgeous kitchen," the agent said.

If the seller had consulted Green beforehand, he might have been able to obtain a higher price. Green would have advised him to upgrade the flooring and spend less on the refrigerator.

"I'm constantly telling my clients to call, even if they are only remodeling for themselves," she said. "I see hundreds of homes each year, including brand-new ones. I can tell them areas to spend (on) and areas not to. This will benefit them if they ever sell. After all, another set of eyes at no cost is a bonus."

That's certainly sound home-improvement advice. And here's some more:

-- DIY: The desire to do the job yourself rests largely with saving money. If you have the know-how, it's fine to do the work. But if you are a novice who doesn't have a lot of time to correct your inevitable mistakes, hire a professional. It could be money well spent.

Ditto for full-scale remodeling projects. A qualified contractor can take your ideas and visions, tweak them where necessary, and turn them into reality.

-- Tools: Equipment is a big part of the equation. You need the right tools for the job. Don't try to make do with a hammer when the project calls for a saw. Again, professionals have whole toolboxes full of the right equipment.

-- Safety: Climbing up on your roof is dangerous. And so is tinkering with electrical or natural gas systems. Not only can you hurt yourself if you don't know what you're doing, you also can create safety hazards that could destroy your house -- and those in it. And if you don't handle water-related projects properly, the result could be leaks that cause costly damage.

-- Permits: Almost everything you do to your house these days requires a building permit -- even simply replacing one garage door with another. Don't try to avoid it.

Permits help ensure that the construction is safe and meets minimum standards (codes). When permits are issued, building inspectors will drop by to make sure the work has been done properly.

You may be able to get away without obtaining permission from the proper government agency, but if your potential buyer asks about a permit and you can't produce one -- or your town's or county's building department doesn't have one on file -- chances are, your buyer will lower his offer or walk away entirely.

Moreover, if it's obvious the house has been renovated but no permits were pulled, banks are likely to refuse to finance your buyer.

Here are some relatively inexpensive steps, tried-and-true but in no particular order, that sellers can take to maximize their selling prices and find buyers faster. Do all of them, and your place may look so good that you might change your mind and decide to stay a few more years:

-- Paint or re-stain the front door so it looks brand- new. Remember the adage: You don't get a second chance to make a first impression. And you want that first impression to be clean, if not socko.

-- Along the same vein, make sure your plants and shrubs are trimmed and neat, and keep the grass mowed. In the winter, some folks have gone so far as to paint their lawns green so the pictures that accompany their listing are vibrant instead of dull.

-- Don't forget to clean your gutters, especially if you have little plants growing out of them.

-- Consider re-caulking outside around the windows and doors, especially if the old stuff is cracked and pulling away.

-- If your sidewalk, driveway or deck is stained in any way, don't just power-wash the bad spot; do the whole thing so it looks new.

-- Paint goes a long way, which is why you should at least paint the key rooms -- the kitchen, baths, living room and master bedroom. If you have enough lead time, paint one room per weekend so you won't be overwhelmed. But plan to take some extra time for the kitchen and baths. They take longer to paint because of all the angles. If you clean your equipment properly, you can use it over and over again.

By the way, don't do what a former neighbor did and paint one secondary bedroom pink and another blue. Use the same neutral colors throughout. And for goodness sake, paint the ceilings and trim bright white. My ex-neighbor didn't. He painted everything -- including the ceilings -- the same color. Ech!

-- While painting, remove all the hardware and replace them with new locks, doorknobs, hinges, doorstops, switch plates and plug covers.

Again, this will make the place look almost brand-new. Yours truly once went so far as to trade out his old, flat, ugly luan doors for newly painted (white, of course) six-panel colonial doors.

-- Take a good hard look at your windows and screens. If they are not spotless, clean them. Admittedly, this is a laborious task, but it is worth it, even if you have to spend a few hundred dollars for a professional to do the job.

-- Now that the windows are clean, make sure you open the curtains and blinds before every showing so the sun can shine in.

-- Turn on all the lights for each showing so the house appears open and bright.

-- In the kitchen and baths, consider gleaming new faucets and fancy new knobs and drawer pulls. You can change them out in minutes. While you are at it, re-caulk and maybe even re-grout the bath tub and shower. Nothing turns people off like black or moldy strips of old caulk. Yuk!

-- Also think about new light fixtures. You can find relatively inexpensive fixtures at your local hardware or big-box store, which will also serve to brighten up your house. If you don¹t replace the old ones, make sure you at least clean the glass.

-- Now is the time to take care of all those other little things you've lived with and are used to -- slowly dripping faucets, chipped doors and nicked countertops, for instance. They may not bother you, but they could turn off would-be buyers.

-- Change your furnace and air conditioning filters. Savvy buyers look at these things as indicators of just how well you've taken care of your property.

-- Get ride of the clutter. This is a big one. Everyone has clutter ­- stacks of old magazines you intended to read but never got to, small appliances stacked together on a kitchen counter, and toothpaste, hairbrushes and the like gathered on the back of the toilet. Toss the reading material and put the appliances away under the counter where they belong.

Don't forget to work your magic in the garage and storage areas, where things tend to pile up over the years. You may not mind parking in the driveway or on the street, but a buyer may walk if he can't see himself bringing his vehicle inside to sleep at night.

And the same goes for your closets. If your clothes are jammed inside and shoes are piled high on the floor, the closet will appear too small, even if it really is ginormous.

-- A great way to get rid of stuff is to have a yard sale. You could easily make a few hundred dollars and clean your house at the same time. You won't believe what people will buy. At my last yard sale, someone bought the rubber stamps I had made with my children's name on them. She didn't care what they said. She was a teacher who bought them to use by her handicapped students to build their hand-eye coordination.

What you don't sell, you can give away. There are people who will come in at the end of your sale and cart away everything that's left.

-- Move your furniture back so the rooms look larger. This is part and parcel to "staging," and if you don't have an eye for this, consider hiring a professional who will help you put your home's best foot forward by maximizing its attributes and minimizing its faults.

-- If you have a particularly energy efficient house or have been energy conscious, make a list of your previous two years of power bills so you can show prospects your costs relative to your competition. A buyer may not live the way you do, but at least he will know what's possible. Skip this step entirely if you live in a gas-guzzler or you leave the doors open with the air conditioning running.

-- Consider having a home inspection. This will alert you to bigger things that should be corrected before you put the house on the market.

Most buyers will hire their own home inspector. But if your place gets a clean bill of health, you can show it to them, and maybe they won't bother. At the very least, though, you will have a chance to address issues before they become sticky bargaining points.

-- If you have saved those booklets and instruction manuals -- my wife does! -- put them together in a kitchen or laundry room drawer and make sure you show them to prospects. At the very least, this is another indication that you have taken care of your nest.

A few weeks ago, Mark Paskell, a former independent Massachusetts home inspector who now teaches contractors how to handle customers and insurance claims, was asked to deal with what was believed to be a low-ball insurance company estimate.

The company's adjustor wrote up an estimate for $8,000. But after carefully inspecting the damage himself, Paskell says he "found numerous omissions and discrepancies." He ran the numbers for the visible damages alone, and his estimate was just shy of $80,000 -- nearly 10 times what the insurance company offered.

"I fear that this is (one of) many cases where homeowners will be left out in the cold with insufficient estimates to repair their homes," says Paskell, aka the Contracting Coach.

He's probably right. After a recent workshop, Paskell says he received numerous calls from remodeling and repair contractors about incomplete claim offers that left out damage. And not just hidden damage, but damage that was in plain view.

"Contractors have shared with me over 40 claims in the past two weeks where the insurance offer is less than 50 percent of what it will cost to repair visible damage," he says.

All of which begs the question: What's a homeowner to do if he suspects his insurer's estimate of damages is, shall we say, a little bit light?

For starters, don't believe you have to accept the company's estimate. If you do, you could be forced into making only part of the repairs, or putting up your own money to make all the necessary fixes.

"Insurance adjuster estimates are not to be trusted," says Paskell. "Never take the first offer. ... It is always lower than what they are obliged to pay."

If you believe you are being shortchanged or that the estimate is incomplete, call a contractor who is licensed, insured, registered and who understands the insurance process, and ask him to estimate the cost to repair the damages. The alternative is to hire someone who will do an incomplete job, leaving you less than satisfied.

Another choice might be to hire your own insurance expert. Known as private adjusters, these licensed professionals advocate for policyholders in appraising and negotiating claims. They work much like lawyers, taking a share of whatever settlement they can wrangle from the insurance company. They know what to look for in your insurance coverage and how to tussle with insurers.

Another good idea is to check the credentials of the insurance company's adjuster. Often, when there's a weather catastrophe such as a flood or tornado, insurers will bring in additional adjusters from other parts of the country.

The idea is that with the extra adjusters, claims can be paid more quickly and owners can get on with their lives. But sometimes, the out-of-state adjusters are unfamiliar with local building codes and techniques.

Just as you have the right to ask for an appraiser who is from the area and has complete knowledge of it, you have the right to request the same from your adjuster. You may have to wait longer, but it could be worth it.

Paskell has identified several tactics used by insurers to rip off their customers:

-- The adjuster fails to assess all the damage. Some "leave things out on purpose," the Contracting Coach says. "Homeowners who are not familiar with the complicated claims process do not always know what is covered."

If that sounds like you, you may never know if something should be repaired or not unless the adjuster mentions it.

-- The adjuster writes an estimate solely for the damaged area, leaving out connected walls, ceilings and finishes. For example, the estimate might cover replacing a bathtub, but not the wall tile abutting the tub. Or it might call for painting one wall rather than the entire room -- or for just one coat of paint when professionals would apply two.

Insurance companies are supposed to bring their policyholders' properties back to their pre-loss condition, Paskell explains. Doing an incomplete job could leave you, as in the case of the examples above, with mismatched tile or walls.

-- The adjuster leaves out the cost of required permits. You need permits for practically everything these days. If the insurer doesn't pay for them, you will have to, and that's money out of your pocket.

-- Companies use a software product with pricing that is fixed by category and geographic area. Paskell says contractors who carry the legal costs of doing business usually can't work for the rates suggested by this program. Indeed, with those kind of rates, he says, you are likely to attract unlicensed, uninsured contractors who bend the rules or ignore them altogether.

-- If your policy calls for "loss of use," and you cannot occupy your home while the repair work is underway, the insurer should pay you up-front for the cost of living in comparable accommodations until the work is complete and you can move back into your house.