Fire investigators earlier this month were investigating the role construction built without permits may have played in a Los Gatos home fire that took the life of a Santa Clara County Fire Department captain.

While that was later ruled out as the cause of the fire, it does bring to light an important issue: It's illegal to build or perform most home improvements without a building permit.

You must obtain a permit for both do-it-yourself projects or work that's hired out because the permit process triggers building code compliance requirements.

Building codes are a minimum set of standards for the design, materials and building techniques created specifically to protect the health and safety of anyone occupying buildings. Depending upon the jurisdiction, permits are required for something as simple as installing a dimmer light switch or water heater installation to constructing a 3,000-square-foot home.

Home owners typically fall back on penny-wise-and-pound-foolish bottom-line reckoning to justify circumventing the legal building process.

* The remodeling boom creates permit-issuing backlogs in building and permit offices. Time is money, so some home owners skip the permit to save on both.

* Permits themselves can cost hundreds of dollars and the paperwork begins a recording process that can result in a higher assessed property value, increased property taxes and the need for more homeowner insurance coverage.

* The growing home improvement demand allows professional home improvement companies, architects, material suppliers and related professionals to charge more for their work and materials, so homeowners cut corners by not getting a permit.

Not only is that illegal, the misguided penny pinching overlooks the fact that any immediate savings realized by skirting the law could end up costing much more and bring on some long-term liabilities.

Generally, to obtain a permit, you must submit a building plan or for smaller projects, a description of the work to be done. Provided the plan complies with the codes, the building department issues a permit. That triggers one or more inspections of the work in progress or upon completion or both, depending on the job. Building inspectors want to make sure the job complies with building codes' mandates for building materials and techniques.

Beyond the health and safety benefits of code-complying building, a compelling reason to obtain a permit is the cost of not obtaining one.

Overworked building departments don't have the time or staffing to conduct foot-patrol looking for violators, but along with fires, floods, earthquakes and other disasters that prompt a building inspector to come calling, there are a host of other events that can lead to discovering illegal construction.

If a home buyer hires a home inspector to examine the condition of the house you are selling and uncovers home improvements, to protect their investment, the buyer can request a copy of the home's permit record. Each permit typically includes the address of the building, the contractor, the type of work being done, square footage, inspection dates and status of the work.

Appraisers also seek permit records to learn if significant renovations should affect the value of a home. In both cases, illegal work can stop an escrow cold.

What's more, you and your agent are by law required to disclose any known conditions that could affect the value or salability of a home listed for sale. If the buyer thinks can prove you knew about the illegal work, but didn't disclose it, you could get sued.

If the buyer doesn't discover illegal improvements until after the deal closes and the local building department decides not to approve the work, a chunk of the home's value could become a legal issue. Any difference in value based on illegal work can become a point of litigation.

In another scenario, during a building official's scheduled inspection of a perfectly legitimate home improvement, he or she could also turn up older illegal work. The building department could then "red tag" the job and issue a stop-work order.

If an inspector suspects illegal work, you could have to pay for the cost of any inspections required to make a further determination. You could have to remove dirt along the foundation so it can be checked. You may have to tear down sheet rock inside so the inspector can look at framing, insulation, wiring or plumbing.

If the work is deemed illegal, you must legalize it before you can sell the home and, again, that also could mean tearing out old work.

If the illegal handiwork is yours, costs can continue to mount. The building department could levy higher punitive permit fees as well as fines.

In any event, before you can obtain a legal permit on old work, you'll have to hire an architect, engineer or other professional to help draw up plans.

Even if unpermitted work complies with current building codes, building departments often issue only a statement of compliance—not a permit. Because the statement applies only to the visible work, a lender or buyer may not be satisfied and demand that you obtain a permit.

Again, that could mean tearing out the work and rebuilding with a permit—which is what should have been done in the first place.

Real estate writer Broderick Perkins, executive editor of San Jose-based DeadlineNews.Com, writes regularly for this newspaper.