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Built-in Ovens

Wall ovens can be difficult to install because they're heavy and have to be maneuvered into tight openings. The tolerances are exacting — even more so than for other appliances. If the opening is just a little too small or slightly out of square, the oven won't fit. And if it's too big, the trim won't cover the gap.

Like all appliances, ovens require dedicated circuits. The electrician roughs in a wire that is later routed into the cabinet. The oven comes with a flex conduit with conductors ready to be hard-wired to a junction box in the back of the cabinet just before installation.


An electrician makes the 220-volt connection to a built-in convection-microwave oven.


The electrical box will be mounted in the back of the cabinet, which will also contain a conventional built-in oven, shown here being lifted into place.

Undercounter ovens are installed the same way as wall ovens; the only difference is that they go under a counter. A gas oven should be connected to a dedicated 110-volt circuit and to a gas valve in an adjacent cabinet.


There are two kinds of built-in microwaves: models that can be installed only in cabinets, and models that can sit on the counter or be field modified for installation in a cabinet. Field modifying a microwave means installing an optional vent that redirects the exhaust from the back (where it's typically located on countertop units) to the front, and adding trim to cover the gap between the appliance and the cabinet.

For either kind of microwave, you have to provide a specific-sized opening and electrical power in a specific location. Typically, the opening is much larger than the appliance, so there's room to attach venting. The hardest part of this installation is lifting the unit into place.


The author lifts a microwave into a cabinet, which for venting purposes will remain open from below.


The microwave is held in place from above and will be plugged into a 110-volt outlet.

Microwaves draw a lot of amperage and — like any appliance — require dedicated 110-volt circuits. A large built-in unit must be hard-wired; a small one has a power cord that plugs into an outlet you provide.

The most common wall-mounted application is an over-the-range microwave/ventilation unit. These appliances hang from brackets screwed to studs in the wall. Once in place, the ventilation fan should be connected to a metal duct that runs to the exterior. It's important to use the correct-size duct and not to exceed the maximum run or number of fittings allowed by the manufacturer.


Updraft ventilation systems are typically mounted on the wall or — for island installations — hung from the ceiling. Wall-mounted updrafts are the simplest to install: They're secured to the wall or to adjacent cabinets and then connected to the duct and a dedicated 110-volt circuit.

Island units are a little more complex. The duct must come out of the ceiling exactly where the hood will be; blocking must be installed in advance so there's something to hang it from. Most units are designed to fit standard flat ceilings, so if a ceiling is sloped or especially high, a duct cover may have to be custom fabricated.


Since this vent hood wasn't tall enough to reach the ceiling, the author extended it with metal angles and a vertical run of duct that will be hidden behind a custom-fabricated cover.


The hood plugs into an outlet in the ceiling above.

The motor can be attached to the unit itself (the most common and least expensive approach) or installed remotely on the roof or sidewall. One advantage of a remote installation is that it keeps the motor noise out of the kitchen.

Downdraft models. Although not quite as popular as it was once, downdraft ventilation is still a good choice for island-mounted cooktops when the presence of an overhead hood would be objectionable.


This downdraft vent ducts through the bottom of the cabinet.


And connects to a remote fan and motor on the outside wall.

Some ranges come with the downdraft unit built into the chassis. Cooktops, however, require a separate downdraft element. Components must be compatible; I've found it's best to work with an appliance dealer who can specify what will work.

Among the details you need to know to plan the installation are the size of the opening in the counter, the size of the cabinet, and the path the duct will take. The cooktop and ventilating unit have to share the same opening, so it must be sized accordingly. Most downdraft/cooktop combinations are designed to fit inside a standard 24-inch cabinet. If possible, I specify a slightly larger cabinet, to provide more room for the appliance and ductwork. The downdraft unit will be smaller, lighter, and easier to install if the motor is mounted remotely.

Ductwork. Running the ductwork is usually the hardest part of the installation. Because the pipe run is a straight shot up from the hood, it's easiest to vent through the roof. If the space above is finished, though, you have to go through the sidewall. Every manufacturer specifies the duct size, maximum duct run, and number of elbows allowed. Exhaust fans are designed to work with rigid metal pipe, so don't use flexible duct. It's critical to do accurate layout at the rough-in stage; once installed, metal pipe is hard to move.

Ideally you will be able to avoid floor and ceiling joists. If not, consult a structural engineer about making changes to the frame. On one recent remodel we had to cut ceiling joists and make other modifications to help the 10-inch duct avoid existing plumbing.


It's easiest to run an exhaust duct through unfinished attic space.


Ceiling runs are harder; to avoid lights and plumbing, this 10-inch duct had to jog between bays and through a joist — necessitating an engineered design that involved doubled 3/4-inch subflooring above, and several sistered members.

If the duct passes through unheated space, such as an attic or crawlspace, it should be insulated to prevent condensation. Most ventilation systems come with built-in dampers; to prevent critters from getting in, a damper should also be installed where the duct exits the building.


With dishwashers, the important distinction is whether they are of American or European design. American-made units require 24-inch openings; European models require 23 5/8 inches. If you plan for an American model but install a European one, you'll end up with an ugly 3/8-inch gap. I once had to move a cabinet after the granite countertop had been installed just to rectify the 3/8-inch discrepancy.

Double-drawer units stand on the floor, same as traditional dishwashers. Single-drawer models sit on top of short cabinets, much as range tops do.

Dishwashers require a dedicated 110-volt electrical circuit, plus a hot-water supply and waste line. If the unit is hardwired, a wire is run into the opening at rough-in and the connection is made from the front at floor level after the unit is installed. Many dishwashers now come with an attached plug, so they can be plugged into standard outlets. It's best to wire the outlet into an adjacent cabinet; that way, the appliance can be easily disconnected for future service.

I've installed only a couple of dishwashers that weren't located next to the sink cabinet. In both situations, we still used the plumbing at the sink location. Plumbing rough-in is fairly basic: Fresh water is supplied via an extra hot-water stub-out. An angle stop is installed on trim with a flexible water line running to the dishwasher through a hole in the side of the cabinet. A flexible waste line runs through the same hole and ties into the sink's P-trap or a dedicated waste line.

Air-gap device. In our area the code requires that dishwashers have an air gap in the waste line to prevent wastewater from being siphoned inside. The standard way to achieve this is by installing an air-gap device in the counter. However, many of my clients absolutely despise having an extra hole in the counter, so in their kitchens we install an air-gap fitting called a Johnson Tee (Johnson Industries, 800/548-6895) during rough-in. The product includes a 1/2-inch copper pipe that runs from the sink cabinet location and connects to its own waste pipe in the exterior wall. When the dishwasher is installed, the drain hose is connected to this copper pipe.


When customers don't want a dishwasher air-gap device on top of the sink counter, the author installs a Johnson Tee, an air-gap fitting approved by the Uniform Plumbing Code that allows a 1/2-inch copper drain line to connect directly to the ABS standpipe.


The dishwasher drain connects to the copper drain line.

I consider the Johnson Tee a great alternative to a counter-mounted air gap, but some plumbers refuse to install it because they claim the waste line is easily clogged. My experience has been that if homeowners scrape their plates before loading the dishwasher, clogging will not be a problem.


Standard refrigerators require nothing more than a dedicated electrical circuit, a space against a wall, and perhaps a water line for an icemaker. The placement of the electrical outlet is not critical; I usually put it about 4 feet off the floor.

There are two main ways to run the line for an icemaker. The first is to use an in-wall shutoff valve that the water line connects to. The second is to run soft copper pipe from the sink cabinet to the refrigerator location — a method I prefer because the water can be shut off without moving the appliance. I also recommend putting a water filter in the line that runs to the icemaker.

Built-in refrigerators have become very popular in high-end kitchens. Their low profile allows them to be integrated into standard 24-inch-deep cabinetry; the maker provides a specific size opening and specific locations for the utilities.

With a Sub-Zero — one of the most common built-in refrigerators we install — the water connection is made in the center of the opening near the front of the unit. I strongly recommend putting a water shutoff in the sink cabinet so the appliance doesn't have to be moved if there's a leak (a standard 36-inch-wide Sub-Zero weighs about 600 pounds). The compressor is at the top of the unit, so the 110-volt outlet needs to be at a spot high on the wall. Anti-tip blocking may be required at the top of the opening.


The author installs an anti-tip bracket for a Sub-Zero refrigerator.


A soft copper water line is run to the front of the opening, where it will connect to the icemaker.

Built-in refrigerators are installed after all the adjacent cabinetry is in place. First, the flexible water line is bent down and slid underneath the appliance. Next the unit is rolled into the opening (finished floors should be protected). Once the refrigerator is pushed all the way back, it must be leveled. With the upper grille removed, the power cord can be plugged in; then the appliance can be powered up and the upper grille replaced. Finally, the water supply is attached from the front of the appliance and the toekick cover is installed.

Miscellaneous Appliances

There are plenty of other appliances you might be asked to install, including trash compactors, warming drawers, wine coolers, and espresso machines. In most respects these appliances are similar to the more common ones described above: All require electricity, and some also require water. The bottom line is that you need to know in advance which models will be used, and then do your rough-ins and cabinetry installations in accordance with the appliance manufacturers' specs.

David Getts owns David Getts Designer Builder, a remodeling company in Seattle.