When shopping for windows, you always consider styles, colors, materials, and energy efficiency. But because most people don’t install their own windows, one of the most important decisions you’ll make is who will be installing the windows. Understanding how window installation works and what the best installation practices are helps immeasurably when it’s time to hire a window installation professional.

When quality windows are installed properly, they can last for many years, add beauty and value to your home, and make your home more energy efficient. However, if windows aren’t installed properly, you may have water damage, the windows may fail, and you may end up with structural damage. This article is intended for installation of new construction and full frame replacement windows. This information isn’t meant for insert replacement widows, which we also supply.

What happens when windows are installed improperly?

  • Poor performance of the window — energy inefficiency
  • Leakage, which can go undetected and cause rot
  • Damage to interior floors, walls, and trim from leaking windows
  • Warranties can be voided
  • Window doesn’t operate properly
  • Locks don’t line up

Here at Ring’s End, we sell the best quality windows and want you to get the most out of your investment. Even though you probably won’t be installing your own windows, it really pays you to be informed. Following are the Five Steps to Proper Full-Frame Window Installation, written from the point of view of the installer, plus videos showing how each stage is accomplished. By making the effort to understand proper installation, you can ask the right questions of your contractor before the job begins, during the installation proper, and at the final sign-off. This should help ensure that your windows will be installed properly and will give you many years of optimum performance.

 1. Make Sure House Wrap is Installed… Properly!

A window is filling a hole cut in your house. That hole needs to be thoroughly sealed to make sure no water gets in, which would adversely affect window performance. House wrap provides a primary line of defense against water. Used over the house sheathing and under the siding, it sheds any water that gets under the siding. Make sure that a water resistant barrier is used and that it’s installed correctly by having the printed side of the barrier facing the exterior of the house. Use cap staples to attach the barrier to the exterior for best results. Start wrapping the exterior from the bottom and work your way up. When a sheet of the barrier isn’t tall enough to cover a space, layer it above the lower sheet and give it an overlap of at least six inches. Make sure that seams are taped!

When installed correctly, the water resistant barrier allows moisture that builds up inside the house out, but doesn’t allow outside moisture in. By starting the barrier at the bottom of the exterior and layering additional barrier on top with an overlap, water will shed off the exterior of the home.

2. Cut the Water Resistant Barrier With An“I”Cut

To make room to install the window, the house wrap needs to be cut. It used to be that using an X-cut in the water resistant barrier was the best way to make an opening for installing the window. Now there’s a better way – the I-cut. Using an I-cut allows you to wrap the top of the frame and install a sill pan at the bottom. This helps protect the top and bottom of the frame that holds the window. Make sure to keep the excess moisture barrier for later.

3. Install Sill Panning

Sill pans are used to protect the window frame from moisture by collecting moisture that may cause rot and decay and allowing that moisture to escape. There are 4 types of sill pans, so make sure that you have the right one for your windows. Ring’s End can help you if you’re not sure which is right for you.

To install a sill pan, lay down a couple beads of construction adhesive on the rough sill; then lay down beveled cedar siding or clapboard with the thicker side facing the interior of the home to help facilitate drainage. Install the sill over the cedar siding or clapboard. Then attach the house wrap to the stud with construction tape also use construction tape on the face to secure the bottom corners of the house wrap to the sill pan.

4. Installing the Window

The first step is to unwrap window. Cut down the side of the window to prevent damaging the window’s finish. Remove the installation instructions and remove the corner gaskets; remove from side jam of window, which are stapled on.

Check the window specifications to make sure the window is the correct size for the opening. It is also smart to dry fit the window before adding any adhesives or other materials to make sure it fits in the opening.

Add sealant around the window, on top of the sill pan, and behind the jam nailing flanges and head-nailing flange. Don’t place sealant behind the sill (bottom) nailing flange because you want to allow moisture to drain from the bottom.

Place the window in the opening and then make sure it is level and plum. Someone should also be on the inside of the window to set shims wherever needed to level the window before it is fastened.

When fastening, start at the bottom of the nail flange with a roofing nail and tack the bottom 2 corners and then the top to corners. At that point check to make sure side rails are level. Then nail the centers of the side nail flanges. After the corners and centers of each side are nailed in, continue around the nail flanges in an alternating pattern until the entire nail flange has nails hammered in.

5. Weatherproofing the Outside and Insulating The Inside

Weatherproofing the exterior of the window is critical for ensuring that your window is sealed against the weather. Take the corner gaskets that were set aside earlier and attach them to the outside window corners. The corner gaskets should roll up the side of the window slightly to prevent any possibility that air or water will get through.

Once the flanges have been correctly applied, attach a self-adhesive flashing tape on the outside over the house wrap. Always have the layer above overlap the layer below. Apply the side jamb flashing tape first, then the head flashing tape second. Use building tape to seal the top of the head flashing tape, so you’ll have two layers of tape at the top of window. Bring the flap of moisture resistant barrier that was cut earlier in the process down over the top of the head of the window for one final layer of protection at the top. The top of the window is where it’s most prone to moisture damage, so you want to make sure it’s thoroughly protected.

As a final step for weatherproofing the exterior, add a strip of moisture resistant barrier (the excess that was cut off earlier in the process) to the bottom of the window. Only tape it at the top so that water doesn’t get trapped at the bottom.

On the interior of the window, insulate the gap between the new window frame and the frame of the house. To do this, use a low expansion closed cell foam to go around the window on all 4 sides. Then go around the window with loose bat fiberglass insulation to pack the remaining gap of the wall.

Common Problems With Window Installation:

  • Not using cap staples to attach house wrap to wall. Wind can cause house wrap to rip off wall. Cap staples help hold house wrap tight.
  • Not using materials that are compatible with each other – brands flashing, house wraps and tapes have been tested to work together. Don’t mix brands.
  • Not making sure that windows are plumb and square.
  • Not nailing the window off properly. Fill in all holes in the nail flange! There are those that will only nail a few and it cause the window to sag. Nails are inexpensive; failing windows are not.
  • Using expanding foam while insulating the interior of the window instead of low-expanding foam. Expanding foam puts pressure on jams and the window will not operate properly. Using low-expanding foam with fiberglass insulation will get optimal results.
  • Using wood shims rather than composite shims under the window. Wood shims can collect moisture, so make sure to use composite shims.
  • Improper flashing and not using the right shims are the top issues we see here at Ring’s End.

Make sure to talk to your building professional about how they install windows before agreeing to have them install windows in your home. For more information on proper full-frame window installation, consult the Ring’s End professionals at any of our Window and Door Showrooms. Visit the Windows page of our website for more information about the types and brands of windows we sell.