How to Measure for and Install Replacement Windows: A DIY Overview

January 31, 2010

The major expense of most home improvement projects is in the labor. However, if you know how to measure for replacement windows, you'll be one step ahead of the rest. And if you know how to install replacement windows, you may achieve some serious savings.

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Despite the challenging sound to this project, most home improvement Web sites label replacement windows a project for the intermediate do-it-yourselfer (DYIer). Knowing how to measure for replacement windows requires some basic math and a tape measure. Knowing how to install replacement windows is a bit more involved--but still doable!

How to Measure for Replacement Windows

Measuring is perhaps the most critical part of the job. Mess this up and you'll be scrambling for materials at an added expense. But you won't believe how easy it is to get this one right. Lowe's tells you how:

  • Jamb to Jamb for Width. Measure inside the jamb from one side to the other; repeat this action at the top, middle and bottom of each window
  • Sill to Head Jamb for Height. Measure from top of the sill to bottom of the head jamb; again, repeat at the right, middle and left
  • Less is More. Always take the smallest of the three measurement for your baseline; you can shim the gaps

How to Install Replacement Windows

This Old House offers an exhaustive sequence of photos and descriptions explaining how to install replacement windows in 12 steps. Here are the three main types of replacement window kits you'll most likely encounter:

  • Sash Kits. Gives an old frame new moveable parts
  • Insert Replacements. Window and secondary frame ready to be installed
  • Full-frame. Includes head jamb, side jambs, and sill

Always follow manufacturer's guidelines when installing a replacement window to ensure safety and the preservation of warranty.

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