How to Add a Garden Window


A garden window (sometimes called a box window) extends the win­dow area about a foot outward from the house. It makes the room it’s in look larger and more spacious. It also adds a certain elegance to the house.

Will you recoup the money you spend adding a garden window? The addition will likely cost between $500 and $1000, but it’s hard to say whether your property will increase by that amount as a result. Certainly, adding the window will make your home more livable while you’re in it and more salable later on.

Where Should I Add the Garden Window?

The easiest place to add a garden window is where a regular window already exists—particularly if the existing window and the new win­dow are about the same size.

Garden Window

The advantage here is that you’ve already got the framing for the window. Demolition work can be held to a minimum. You may find that all you need to remove is some of the exterior skin of the home and a bit of the drywall inside. As a result, the patching required after installation will also be minimal. On the other hand, you may discover that there is no existing window where you want to place your garden window. Or the existing window is too small. (It’s much easier if it’s too large!)

If the window area is too small, you’ll need to remove part of the wall where the new window is to go and then frame it. Begin by tearing out the existing studs. Next, put in a header of appropriate size (a heavy beam over the window that helps carry the weight of the roof formerly borne by the studs) and box the window area. The framing itself is neither difficult nor complicated; you can do it yourself or call in a carpenter or handyperson. In the process, however, you’ll end up needing to repair the entire wall area both inside and out.

Do I Need Permits or Approval?

Check with your homeowners association, if you have one, since the work you’re doing will extend the living area outward and will change the appearance of your home. In a condo situation, you will definitely need approval.

Further, if you’re going to reframe the window area, you’ll defi­nitely need a permit from your local building department. On the other hand, if you’re simply replacing one window with another of the same overall dimensions, a permit may not be required.

Any time you use glass in an area where it might be bro­ken, the building code requires it to be safety glass (either tempered or laminated). These areas include skylights, bathrooms, and living areas where the window is below knee height (and someone might accidentally kick it). Garden windows do not usually fit into this class. However, moving plants into and out of a garden window can pose a danger to the glass. You may want to consider using safety glass, despite its higher cost.

What Type of Window Should I Choose?

In extreme climate conditions (hot or cold), you want as much insu­lation as possible from a window. If you live in the North, you want to insulate against cold in the winter. If you live in the South, you want to keep out heat in the summer. Insulating windows will cut down substantially on your utility costs. Don’t make the mistake of thinking that because a window is small compared with the overall wall area of the house, it doesn’t count in terms of thermal loss. It does.

The first U.S. observation station in Antarctica had a small glass dome open to the elements to let in light and to allow those inside to see out. It took as much energy to heat the dome as it did to heat the entire station of more than a dozen men working beneath the ice. Similarly in a home, most of the heat conductivity (loss) will come by way of the windows.

Probably the most common form of window insulation is double-pane glass. The two panes have a dead air space in between that is hermetically sealed. This almost cuts in half the conductivity of sin­gle-pane glass. Triple-pane glass reduces conductivity even further. Adding an inert gas, such as argon, also helps. Inert gases are heav­ier than air, meaning that their molecules move slower, thus reduc­ing conductivity.

However, because of the design of garden windows, the added weight of double- or triple-pane glass may make its use impractical and costly. One alternative is Low-E (low-emissivity), high-transmittance glass, which has a special coating to reduce heat conductivity. At the same time, almost all natural light is still able to come through.

Low-E glass is high tech and produces some amazing results. Whereas a single pane of glass has an R rating of 1, usually Low-E glass can have an R rating anywhere from 4 to 7 or more. Further, because the glass has just a coating, its weight is relatively unaffect­ed. Except for the added cost, Low-E glass is probably the best choice for a garden window.

What Type of Frame Should I Choose?

You have all sorts of choices in terms of frames. They can be wood, polyvinyl chloride (PVC), steel, or aluminum. Important considera­tions are the amount of maintenance required and the thermal qualities of the frame. Again, you are looking for materials that have low (or poor) heat conductivity.

Wood is the traditional frame, but it may not serve well in a gar­den window. To get the required strength to hold the window, you may need to add bulk. In addition, wood is a high-maintenance product. It must be sealed and painted regularly. However, as a poor conductor of heat, wood offers good thermal properties.

PVC is a relatively new product. It is rarely used in garden win­dows because it tends to be flimsy. In order to provide the necessary strength, it must be bulked up, creating an unattractive appearance. Vinyl can be easily painted. On the other hand, it is a good conduc­tor of heat; hence it has poor thermal qualities.

Steel may be used for its rigidity. However, it is heavy and has high heat conductivity.

Aluminum is usually the frame of choice. It is lightweight, sturdy, and virtually maintenance free. It can be anodized in a variety of metallic colors. But it too is a good conductor of heat, and hence has poor thermal properties. Sometimes thermal breaks (essentially dead air spaces) are installed right into the frame to reduce the gain or loss of heat.

What about Installation and Costs?

Installation of a garden window is fairly easy. There are just five steps if you’re replacing an existing window with a garden window that is close in size.

1. Remove the existing window. The amount of work involved will depend on the type of window you have. With an aluminum win­dow, you will need to remove some of the interior drywall around the window frame and then some of the stucco or other exterior wall. Typically the window is simply nailed in place with flanges on the exterior. Remove the nails and it just pops out. With a wooden window, the entire frame will need to be removed. Use a crowbar to carefully separate it from the rough opening behind.

2. Move the new garden window into place. Use shims, if necessary for small differences in size. Get help in positioning the window, since it’s awkward to hold and can be heavy. Be sure to check that it’s level. The last thing you want to do is install a window that’s on an angle!

3. Nail the new window in place. It’s probably a good idea to use screws, particularly on the top, for added strength.

4. Replace and patch any damage done to the exterior wall and interior walls.

5. Finish up. Some garden windows have glass on the bottom. Others are designed to have a countertop that extends outward. Finish out the countertop portion, if needed.

Garden Window

If you’re having a window custom-built, expect to pay big bucks. A single garden window 5 feet wide by 3 feet tall could easily cost you $1000 or more. On the other hand, you can buy a ready-made gar­den window for a quarter to half that price at any one of the many home supply companies, such as HomeBase.

If you buy a ready-made garden window, be sure to check on its insulating qualities. The R rating should appear right on the product.

A garden window will add light and airiness to any room. It is one of the easiest and least expensive ways to “expand” your home.

Filed Under: Home & Maintenance

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About the Author: Jason Prickett loves to write about home maintenance and stuff you can do yourself instead of hiring any professional. His step by step guides will assist you in completing your home maintenance tasks.

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