New Window Installation: 3 Installation Tips For Replacing Sill Frames

Generally speaking, you can expect to have to replace windows in your home every 15 to 20 years if you maintain them properly.  You might want to switch from single pane windows to double pane windows, or you might simply want to try out a different window design. Regardless of what you choose to do when installing a new window, you need to inspect the sill frame and replace it if it is cracked or rotten. The sill frame is a part of the window and plays a crucial role in keeping water out of the home. Here are 3 installation tips to consider.

Store the Sill Frames Properly Before the New Window Arrives

While it might take a while for the new window you've ordered to arrive at your house, you can usually easily get your hands on the sill frame at a local home hardware store. Buying the sill frame first can be beneficial, as you'll need to have measured and cut out the frame to match the windows before the new windows arrive. This will greatly expedite the installation process later on.

If you already have the sill frames you need, you'll need to be extra careful when storing them before the windows arrive. In particular, most professionals recommend covering the sill frame with a tarp and keeping it away from the sun in order to prevent the wood from buckling or warping in shape. If this happens, the structural integrity of the sill frame will be greatly diminished and the frame will no longer be an effective seal. It'll be more likely to deteriorate prematurely, as it will not be able to tolerate environmental and elemental conditions as well as before.

Be Precise When Laying the Sill Frame

You want to lay the sill frame flush with the outside edge of wall or the window. Be as precise as possible in order to prevent water from accumulating on exposed concrete surfaces and migrating into your home. You want to make sure that there are no gaps or surface areas exposed, so double check that the sill frame fits perfectly. Don't settle for anything less than perfect.

To verify that your measurements are precise, get someone else to frame against the outer edge of the wall or the window for you. By doing this, you can make the markings you need without worrying that the sill frame may accidentally shift from its original position during the installation of the new windows. The sill should be angled in a way that any water that does enter can be easily drained. You don't want any stagnant water to be trapped in this area, as it will easily contribute to fungi growth and mold formation.

Use a Seam Sealer

Before you lie down and install the sill frame to the outer edges of the window, you should consider installing a seam sealer first. A seam sealer is basically a strip of foam that lies beneath the sill frame and the outer shell of your house. It acts as insulation and will help enforce and secure the window seal. It will also help protect the sill frame from external factors and conditions.


Installing a new window is a lot of work. After choosing a window design that works for the room and your house, you'll need to consider the structural elements involved. The sill frame plays an important role in new window installations and proper installation is key to having a long-lasting and durable window for years to come. Improper installation will lead to premature window deterioration and water damage to the internal wall structure.