New-home buyers usually don't concern themselves with footings, framing, wiring, ventilation and the various and sundry mundane structural items that go into a house. Those things are the province of the home's builder.

But when you're turning your carport into a garage, extending your kitchen another five feet or adding a second story to your 15-year-old rambler, you are the builder. And as such, you have to pay close attention to your local building codes.

Building codes are a set of minimum design and construction requirements set forth to protect the public health, safety and welfare, and they're rooted in ancient history. Back in the 18th century B.C., for example, the Code of Hammurabi mandated death to the son of a builder whose building collapses and kills the son of the owner.

Today's codes don't carry such weighty penalties, but they are somewhat more encompassing. Generally, they cover structural design, foundations, exits, fire protection, sanitation and roofing, plus the electrical, plumbing and mechanical systems. Some even cover energy conservation.

Only 30 states have mandatory statewide codes, 19 of which allow local jurisdictions to make them tougher. The other 20 states rely on the jurisdictions within their borders to enact their own construction regulations.

The bottom line? If you're modifying the structure in any way, chances are, you'll need a permit. Perhaps even several. Worse, securing permits is often a time-consuming process, and an expensive one.

For one thing, you'll probably have to provide detailed construction drawings, maybe even multiple sets, and they might have to be drawn by a licensed architect. For another, all permits are assessed a fee based on the value of the improvements you are making.

Because of the extra time and money involved, some contractors will suggest that you secure the permit instead of them. Others will exhort you to skip the permit process entirely and get right to work. Neither is a very good idea.

While no jurisdiction will refuse to grant a permit to an owner-occupant who can prove he owns the house and lives in it, it normally doesn't cost any more if the contractor applies, and he can usually get in and out of the local building department a lot faster than you can.

Just as important, if you apply and say you are doing the work yourself, all you have to do is show your local building officials a tax bill or deed. But if the contractor applies, your local building officials will probably check to make sure his license is up to date and his liability insurance is in place.

Applying for a permit is also your assurance that your project will be done right, or at least up to minimum standards. Besides going over the plans before work begins and suggesting ways the job might be done better -- or perhaps even cheaper -- the local authorities will make periodic inspections to make sure the contractor is following the rules.

Some contractors argue that none of this is necessary, that they've forgotten more about construction than anyone on the government dole will ever know, that they don't want to hassle with fees and inspections, that dealing with local building officials is a bureaucratic nightmare.

"If you can't trust me," is a familiar refrain, "then you'd better hire someone else."

To a certain degree, the contractor-client relationship is built on trust. And while the head of the building department in some locales is also the guy who gives out dog licenses, it's best not to allow non-permitted work done to your house, especially if you know little or nothing about construction.

Besides the off-chance that non-permitted -- and, therefore, illegal -- work could fall down around you, there's also the possibility that if the local authorities get wind of what's been done, you could be required to rip everything out and start over.

What's more likely, though, is that you may not be able to sell a house on which structural work was done without a permit. Most states today require you to disclose such a material fact. If you ignore that law, you're still liable to be caught if your buyer is savvy enough to hire an independent home inspector to give the place a once-over.

Even if your buyer wants to proceed -- and assuming he can get a loan on a place that's not up to code, which is problematic in and of itself -- he's sure to demand a major price concession. And if an unsuspecting buyer doesn't find out until later that work was done without a permit, he can demand that the sale be rescinded and sue for damages.

NEXT WEEK: Special exceptions.

Is your market hot?

Every once in a while, local media proclaim that the local market is "on fire." But is it really?

If the report is based solely on the fact that there have been more sales in the current period than in the previous one, then it could be terribly misleading. There's more to a hot market than simply a pickup in transactions.

"Just like a medical diagnosis can be wrong if you are looking at just one vital sign, so can a proclamation that the market is hot -- or cold, for that matter," says Thomas Hoff of Pro Teck Valuation Services in Waltham, Massachusetts.

I asked Hoff about the key factors Pro Teck looks at to produce its monthly Home Value Forecast. He says the company watches nine different data points, detailed below, along with tracking trends and using consistent methodology.

The relative "hotness" of a local market is key information for its buyers and sellers. Luckily, most of the data that Pro Teck evaluates is readily available from the local multiple listing service, so your agent should be able to look at the same info and come up with a reasonable list price for your house (or how much to offer, if you are buying).

But if he or she simply uses comparables -- previous sales of similar homes in your area -- you might want to go elsewhere, or even try to do it yourself.

Here's a quick rundown of Pro Teck's nine key statistics:

-- Sales. The number of sales in a given month is important, but you want to compare it to the same month a year ago. Actually, Hoff uses a three-month rolling average, and compares it to the previous same three months. So, if you are trying to determine whether sales are up in December, you'd look at the average number of sales in September, October and November, and compare it to the average in the period a year ago.

-- Active listings. Here, you want to know how many houses are on the market compared to a year ago and the percentage change. "This is simple supply and demand," says Hoff. "The fewer number of listings make it a hotter market; the more listings, the slower the market."

-- Months of remaining inventory. This is the average rate of absorption, or houses actually sold. It is determined by dividing the number of houses on the market at any time during the previous month by the past year's monthly sales rate. According to Hoff, an answer of five to six months suggests a balanced market. If it's less, buyers should probably expect to pay more than list price; if it's more, you can probably bargain. Vice versa for sellers.

-- Selling price. Determine the average selling price, again using the three-month rolling average as compared to the same period a year ago. Use a rolling average so your number is not impacted by a house that sold for an unusually high or low price. "You want to get rid of spikes so outliers don't impact your figures," Hoff says.

-- Days on market. Again, using the rolling average, compare how long it takes to sell houses now vs. a year ago. If it takes longer, the market is slower.

-- Active price. If the average is rising, supply and demand fundamentals "are at work," Hoff reports. But if it's going down, there's more supply than demand.

-- Active days on the market. Similarly, if the average is going down, it's indicative of a hot market.

-- Sales price vs. list price. Here, you'll want to know the ratio between what houses were listed for and what they sold for. Of course, the hotter the market, the higher the ratio. Anything above 98 is considered pretty good. But if it is trending lower, it's not so hot.

-- Foreclosures. Finally, but still very important, you want to determine the number of foreclosure sales as a percentage of all sales. Five percent is healthy. But once this number rises above 10 percent, it starts to negatively impact the market.

Miami is a good example. Based on the number of sales alone, it looks like a hot market. But 12 percent of its sales are foreclosures, so prices are still depressed. "It's like an anchor dragging down prices," says Hoff.

Forget about millennials. Everything that can be written about that age cohort has been written. So let's move on to Gen Z. They are mostly teenagers today, but they will be homebuyers tomorrow. Or will they?

That's what the Better Homes and Gardens Real Estate franchise wanted to find out with a survey of a small sample of kids ages 13-17, of which there are 21 million or so. The results were heartening.

For example, 82 percent said home ownership is the most important factor in achieving the American Dream. Most adults feel that way, too. But millennials, not so much. And a whopping 97 percent of the Gen Zers polled said they fully expect to own a home sometime in the future.

But how much does home ownership really mean to them? I mean, what are they willing to give up? How far are they willing to stretch? Pretty far, it turns out.

Nearly two out of every five would willingly take their mom or dad to their high school prom if it allowed them to buy a home. And even more telling, a bit more than half said they would gladly give up social media altogether for one solid year if it meant being able to buy.

About a third of all consumers plan to give technology gifts this holiday season, according to the Consumer Technology Association. Spending on technology will increase by about 3 percent to $36.05 billion.

While not as popular as, say, drones or virtual reality, smart house devices such as thermostats and digital assistant devices such as Amazon's Echo will command a roughly 10 percent share of the tech market this year.

Looking for another reason to buy rather than rent? Most automobile insurers charge drivers with good records as much as 47 percent more for basic liability coverage if they are not homeowners, according to an analysis of premiums by the Consumer Federation of America (CFA).

Based on a sampling of quotes throughout the country, the CFA found that premiums averaged 7 percent higher, or about $112 annually, for a 30-year-old "safe" driver who rents rather than owns. Liberty Mutual was the biggest transgressor, hiking premiums $307 a year on average for state-mandated coverage.

The CFA tested rates for minimum liability coverage in 10 cities from seven of the country's largest companies. On average, they charged renters 6 percent more. But there were several instances of double-digit increases, including the aforementioned 47 percent in Louisville, Kentucky, by Farmers.

Geico was the only company tested that did not consider home ownership status, and Allstate actually charged renters less in Chicago.

"Insurance companies should judge you on how you drive, not who you are," said J. Robert Hunter, CFA's director of insurance and a former Texas insurance commissioner. "Insurance companies are penalizing good drivers by hundreds and sometimes thousands of dollars each year based on economic and social status, and the end result is that the poor pay more, much more."

Speaking of automobiles, real estate brokerage firm Redfin has developed a rating system that measures the number of jobs within a 30-minute, car-free commute from a given address.

Called the Opportunity Score -- with 100 representing the home with the most nearby jobs -- it aligns two major lifestyle choices influencing how people live today. One, many people don't want to rely on autos to get to work, and two, being close to jobs means it is less expensive to buy.

For what it's worth, Redfin also has developed a number of other scoring algorithms, including Walk Score, Bike Score and Transit Score, all of which give people a sense of what it's like to live in a particular neighborhood.

Much is said about the number of million-dollar homes. But they don't usually start out that costly, according to the Census Bureau. Only 1,762 houses started for sale in 2015 came with a price tag of $1 million or more.

Last year's count was about half that of 2014, when 3,347 million-dollar manses were started. And it was way, way lower than in 2005, when the number reached its peak at 5,647.

Still, even at that, the number of newly built million-dollar houses represents only 1 percent of the total number of housing starts and a lower percentage of all homes sold.