clock menu more-arrow no yes mobile

Your Basement: Why Add on When You Can Add Under?

Your basement is valuable real estate, and it's an ideal place for the low-cost extra bedroom, family room or workout space you've always wanted

Photo by Ryan Hulvat

Most basements are little more than a place to cultivate cobwebs and store cans of paint. But fixing up a full-height basement can dramatically increase the usable living space in your house at a far lower cost than adding on.

Although costs vary with the size and complexity of the project, remodeling an existing basement starts at about $20 per square foot, a fraction of what it costs to build an addition or enlarge second-floor space with

dormers. And as we show here, basements can be turned into any one of several living areas. That explains why builders like Rick Heim, a Boston-area contractor, won't even use the "B" word. To Heim and like-minded contractors getting on the bandwagon, a basement is a "finished lower level."

Changing a concrete dungeon into a inviting living area is a challenge, and not every basement is a good candidate for finishing. Key considerations for conversion include controlling moisture, adding ventilation and light, and finding a way around hanging drain lines, ductwork and wiring. Although you can do some of the work yourself, most of it is best left to an experienced pro.

<p>An unfinished basement became a comfortable gathering place in this Massachusetts home. Sherri Martinelli, here with daughter Cambria, set out to create a haven for teens.</p>

An unfinished basement became a comfortable gathering place in this Massachusetts home. Sherri Martinelli, here with daughter Cambria, set out to create a haven for teens.

Photo by Ryan Hulvat

Getting It Dry

"If your house has a history of basement flooding," says Newton, Massachusetts, remodeling contractor Paul Eldrenkamp, "you're crazy to consider a basement renovation until you solve that problem." Most water problems, he says, are caused by inadequate control of roof runoff. Eldrenkamp estimates that 2 in. of rain falling on a 2,000-sq.-ft. house produces 2,600 gal. of water. So repairing cracks in the foundation, making sure the gutters are clear of clogs and sloping the ground away from the house will solve a lot of flooding problems. But if water still seeps in, installing or repairing foundation drains might be the cure.

Either of these is a big project that requires excavating around the perimeter of your house. An option is to install drains along interior basement walls. Contractors remove a strip of concrete next to the wall and dig a trench around the outside of the floor. New drain lines catch water and rout it to a sump where it is pumped out of the house or directed to gravity-fed drains if the grade allows it. Eldrenkamp says this type of work isn't cheap, costing $50 to $60 per foot in his area, but it is highly effective at keeping water out of a finished space. Masonry sealers, such as those made by Drylok or Thoroseal, also can be effective in controlling moisture when applied to interior walls. But as Heim cautions, "If you have an ocean coming in, they are not going to stop it."

Radon, a naturally occurring radioactive gas common in some parts of the country, is another consideration when you convert a basement. A simple test will measure the level of radon and indicate whether mitigation is a good idea. If so, radon can be collected by buried drain lines and vented to the outside, much like excess water.

<p>Exercise is the theme of this partial basement renovation in a Boston-area<br> home. Carpeting is an inexpensive but effective covering for steel columns.</p>

Exercise is the theme of this partial basement renovation in a Boston-area
home. Carpeting is an inexpensive but effective covering for steel columns.

Photo by Ryan Hulvat

Meeting Building Codes

Building codes vary, but generally the finished ceiling height in a basement must be at least 7 ft. Codes permit some lower obstructions — structural beams that can't be moved, for example — and building inspectors often are willing to compromise when contractors encounter minor height problems. Your best bet is to contact your local inspector while you're still in the planning stage. The inspector is likely to be more sympathetic when he gets consulted early in the process.

Once height requirements are met, there is still the question of doors and windows for emergency escape, or egress. Building codes typically require one emergency window (or door) in a basement that contains habitable space, though each bedroom needs its own. If you turn a basement into a family room or a home theater, you probably won't need the same number of emergency exits that would be required for a couple of bedrooms. Adding a code-compliant emergency exit can be expensive in a below-grade basement. Although products are available for just this situation, the builder may have to cut through concrete walls to create a larger opening.

Stairways also can be a problem. Building codes usually call for a minimum of 7 ¾ in. for stair risers and 10 in. for treads. Older stairways may not meet these requirements and might have to be replaced, adding to the cost of the project. Some contractors recommend new staircases anyway to make a remodeled basement more inviting. Another consideration: Adding a finished floor might have the unintended effect of lowering the first stair riser, creating a trip hazard. Eldrenkamp says inspectors in his area will accept a lower riser on the first step, but that's also a point to check with the building inspector's office.

<p>Camouflage the Obvious: It's easier to disguise some water lines with paint than it is relocate them. Creative framing in the ceiling of this basement accommodates the oversize exercise equipment.</p>

Camouflage the Obvious: It's easier to disguise some water lines with paint than it is relocate them. Creative framing in the ceiling of this basement accommodates the oversize exercise equipment.

Photo by Ryan Hulvat

Handling Low-Flying Utilities

When plans call for a finished basement in new construction, ceiling height and utilities can be planned accordingly. Remodelers are rarely so lucky. "Typically," says Eldren-kamp, "people do not plumb houses with an eye to renovating their basements." Water lines, air ducts, bathroom and kitchen drains, and supply and return lines for a hot-water heating system all could be located below ceiling joists, where they are smack in the way of a renovation. Contractors have only a few choices: Move them, box them in or leave them as they are.

Wiring and plumbing often can be relocated. But the process is expensive, and it is sometimes next to impossible to move bulky utilities like drain lines and heating ducts. As a result, builders may hide plumbing, heating and wiring runs in a ceiling, wall or closet. Heim tries to make a finished ceiling look balanced in situations where he is forced to box in utilities. For example, if he has to hide a plumbing run on one side, he may build up other areas to create a coffered ceiling. The result is a pleasing detail whose real purpose is not obvious.

And sometimes offending pipes are simply left exposed and painted. "For the most part," Eldrenkamp says, "people have different expectations for the basement." One thing to remember: When tucking water and drain lines out of sight, don't block access to water shutoffs and drain clean-outs.

Because plumbing and wiring can be hard to disguise, many builders turn to drop ceilings. Common to commercial building as well as to residential construction, these ceilings consist of a metal framework suspended several inches below ceiling joists that supports drop-in panels available in a variety of textures and colors. Acoustic panels that deaden sound are widely used, especially if the basement is used as a home theater or a getaway for teenagers. Relatively low cost and ease of installation make this ceiling an easy choice, but some builders think they are an esthetic turnoff. "The quickest way to make a basement look like a basement," says Heim, "is to put a drop ceiling in." He is much more likely to recommend a plaster or a drywall ceiling, just like the rest of the house.

<p>Builders get creative when it comes to hiding mechanical necessities like plumbing shutoffs and electrical panels. A valve is normally hidden behind a removable panel painted the same color as the wall.</p>

Builders get creative when it comes to hiding mechanical necessities like plumbing shutoffs and electrical panels. A valve is normally hidden behind a removable panel painted the same color as the wall.

Photo by Ryan Hulvat

Finished Wall and Floors

Hiding concrete or block behind new walls is the easy part. Building walls that won't encourage mold and mildew, or be damaged by condensation, is a lot harder. Because concrete in contact with the ground is always cool, it can become a condensing surface for water vapor in the warm air escaping from a finished basement. The result? Damp building materials, mildew and, eventually, rot. Air will be musty, finished surfaces ruined. As Massachusetts builder Fred Unger puts it, "If you get a hack to do the work, it's going to smell like gym socks."

Unger, like other contractors, isolates damp concrete walls from the rest of the space with 1 in. of extruded polystyrene insulation, followed by a layer of 6-mil polyethylene. On rough walls, foam insulation can be sprayed on. Impermeable layers of foam and polyethylene separate wall framing from damp concrete or block while giving water vapor no cool surface on which to condense. Other builders may skip the polyethylene vapor barrier even if they use foam insulation.

Joe Stanton, a Rhode Island builder, for example, thinks it makes more sense not to build walls too tight. It's safer, he says, to give walls a way of drying out should any water or condensation collect inside. Fears of trapped moisture also prompt some remodelers to use light-gauge steel framing on outside basement walls. Although builders might differ on these details, they would agree that obvious water problems, such as leaking foundation walls, must be solved first.

Despite their moisture problems, below-grade surfaces often don't need as much insulation as exterior walls built above ground. Even in winter, the temperature of the earth below the frost line might be no colder than 55° or 60°F. As a result, some builders simply skip fiberglass insulation in stud walls if they use rigid or sprayed-on foam.

Alure Home Improvements, a Long Island, New York, remodeling company, uses an entirely different approach in creating finished basement walls. Its growing basement business relies on a wall-finishing system developed by Owens Corning. The system uses fiberglass panels and trim pieces that snap into PVC structural framing

Wall panels are finished in fabric, eliminating the need for drywall taping or painting. Carl Hyman, the company's owner and president, says the system is up to 30 percent more expensive than conventional drywall construction but has a longer life span and easily tolerates the damp conditions found in basements. Maintenance costs, he says, also are lower. Any parts of the system that become wet or damaged can be removed. Despite its practical advantages, the system does not look like a typical wall and might be a tough sell esthetically in some parts of the country.

When it comes to flooring, just about any material will work — tile, carpet, vinyl or laminate. Fewer contractors, however, choose conventional hardwood flooring because moisture in the slab could cause the wood to swell and buckle. Remodelers should apply a masonry sealer before installing any finish floor. Eldrenkamp uses a fairly elaborate system of polyethylene, rigid-foam insulation, 153 sleepers and tongue-and-groove plywood to create a floating-floor system — that is, a floor not directly attached to the slab. It makes for a warm, dry finished floor, but built-up floor systems such as this may not be possible in basements with extra-low ceilings.

Photo by Ryan Hulvat

Lighting Lessons

Basements in homes whose lot is sloped to allow walkout basements can have abundant light. But when illuminated only by small, ground-level windows, basements can be dark and uninviting. A first step is to clear away shrubbery from existing window wells to make the most of what natural light is available. If the basement is served by a steel bulkhead, a door with glass lights can be installed at the bottom of the steps and the bulkhead doors left open, at least in good weather. Similarly, replacing any solid doors in the basement stairwell with glass doors also may help to increase the amount of natural light.

Yet these steps are rarely enough, and remodelers usually add several basement lighting circuits. In basements with plenty of headroom, track lighting can be attractive, even if it used only as accent lighting. But when the ceiling drops to the 7-ft. range, ceiling-mounted fixtures are more likely to be bumped or broken. Fluorescent fixtures can be recessed into a drop ceiling, but they can give a basement an overlit office look. As a result, builders frequently turn to recessed incandescent lighting. "Can" lights are unobtrusive and can be fitted with either spot or flood lamps, and when put on a dimmer switch, they make lighting more flexible than other options.

Lighting by itself uses relatively little electricity, but other amenities may be power hogs. A sauna or steam room may require 40 to 50 amps, quickly maxing out main electrical panels that are marginal to begin with. And upgrading a 100-amp panel to a 200-amp panel can cost $1,000.

Photo by Ryan Hulvat

Ventilation Issues

Musty, damp air may be something that you can tolerate in a basement you visit only occasionally. But once the basement becomes a true living space, some form of ventilation is crucial in controlling air quality. Eldrenkamp likes to use a reversing fan made by Vent-Axia. In the winter, it draws in fresh, dry air from outdoors (the volume of air is low enough so the basement doesn't feel like an unheated shed). In summer, moist air can be pumped out of the house. Hyman's company often uses a wall-mounted air exchanger made by Humidex, which vents cooler, damp air to the outside. If the house already has a forced-air heating system that includes air-conditioning, the basement can be added as another zone. Air-conditioning naturally lowers moisture levels in the air.

Yet another option is to add dehumidifiers, but there are several drawbacks to them. They are more expensive to run than a ventilation fan, and unless a dehumidifier is plumbed directly to a drain line it will have to be emptied periodically. And, as Heim points out, dehumidifiers tend to be noisy.

Fresh air is just as important to boilers, furnaces and gas-fired water heaters as it is to people. These devices often are enclosed in a small mechanical closet. But in doing so, builders will have to add a source of fresh combustion air. Enter once again the code-enforcement officer: It's a good idea for you to check local code requirements for providing combustion air for those devices.

There's a lot to think about when converting a basement into a bright, inviting living area. But once the work is done, you'll never want to leave.

<p>The builder walked away from this potential basement remodel: The cost of dealing with obstructing utilities and water problems was too high.</p>

The builder walked away from this potential basement remodel: The cost of dealing with obstructing utilities and water problems was too high.

Photo by Ryan Hulvat

Dressing Up a Window

It's hard to enjoy the view when all you can see is a curtain of corrugated steel, but that's exactly what you'll get in an average basement window well. Changing that dreary scenery may be easier than you think.

For about $130, you can add a view of the seashore, mountains, woodlands, desert or golf course. Scenic Window Wells' WELLliner (above) is a weather-resistant polystyrene liner that slips into a standard window well. When you look out the basement window, you might imagine yourself in any one of 36 postcard-perfect locales. Liners are available in two sizes, and the flexible sheets can be trimmed to fit. A light kit also is available to keep the scene visible when the sun goes down.

If all you want is extra light, check out the MaxLight2 System ($120 to $160), which promises to increase the amount of sunlight in the basement by as much as 10 times. It consists of a flexible well liner that fits inside an existing window well and a reflection panel that is attached to the side of the house. Sunlight striking the reflection panel is bounced onto the well liner and then into the basement.

Bilco's ScapeWEL provides light as well as an emergency exit from the basement. The high-density-polyethylene window well snaps together and sits in an enlarged well. Its two- or three-tiered design creates shelves that can be used for plants — or as steps during an emergency exit from the basement. Available in several sizes, the 48- to

62-in.-high unit projects from the foundation from 41 to 49 in. A ScapeWEL alone costs from $470 to $660, but count on buying a window and paying for a contractor to cut through foundation walls to create an opening large enough to handle it. That will boost installed costs to $1,500 to $2,000

Where to Find It


Box 1203, Dept. TH1200

New Haven, CT 06505


15 Pine Ridge Ln., Dept. TH1200

Orleans, MA 02653


MaxLight System Inc.

Box 213, Dept. TH1200

Western Springs, IL 60558

Vent-Axia, Coast Products, Inc.

954 Elliott Ave. W, Dept. 1200

Seattle,WA 98119


Scenic Window Wells

11223 McGuire Pkwy., Dept. TH1200

Lemont, IL 60439