How to Install Replacement Windows: A Step-by-Step Guide

How to Install Replacement Windows: A Step-by-Step Guide

Updated: 02.12.2024

By Nina Tsoy

Right now, window replacement is being done with major repair works in the residential construction industry. Perhaps you’re renovating or upgrading your home and realize you need to replace your home windows but don’t know how.

From deciding on the type and size of the window to preparing the opening to installing and securing the window, this blog lays out a comprehensive process for a successful window replacement.

We’ll cover everything you need to know about installing new windows to ensure the new window is installed correctly and sealed against wind and water.

So let’s start and learn how to replace those old, inefficient windows in your home.

SkillCostEstimated Time
Requires a fair amount of carpentry skills and home-remodeling experience; installation is greatly simplified if window is on ground floor and easily accessible from outsideAbout $500 to $600 for a high-performance 36 x 54-inch wood insert replacement window4 to 6 hours to install an average-size window on the ground floor

Safety Tips for Home Windows Installation

It is important to take precautions when adding windows to a house. Be sure to wear eye protection and gloves when doing so. When working on a ladder, do not stand above the rung indicated as the highest rung for standing; also, have an assistant to help you to stay safe.

If you are working with old window weights, take extra care since they could have been cast from lead. Handle the lead weights with gloves and do not cut or abrade them. Once you are done, dispose of the old weights properly.

Materials & Tools Needed to Install New Windows

Installing new windows

Installing replacement windows is a relatively easy and inexpensive task requiring simple tools and materials. You will need a tape measure, gloves, safety glasses, a hammer, a screwdriver, a pry bar, a utility knife, a putty knife, a sheet of ¼ inch plywood cut to fit the opening, caulk, shims, screws, wood putty, and of course, the replacement window.

Depending on the specifics of your home window installation project, you may also need additional materials and supplies, such as a saw, screws, chisels, and sealant. It is important to use the proper tools and materials to ensure a proper installation that will provide you with a weathertight, attractive, and energy-efficient seal.

Basic Window Types

Before starting the project, you should buy new construction windows with detachable nailing flanges or get replacement windows.

New Construction Windows

New-construction windows are typically installed either when a home is under initial construction or when the house is undergoing a major renovation, such as rebuilding exterior walls. These windows come with a nailing flange, called nailing fins, on the outside so the window can be nailed against the wall sheathing.

Some new-construction windows also come with removable flanges, allowing them to be used as replacement windows. To remove the flange, you can score the junction between the flange and the window with a utility knife, then bend it back and forth until it snaps off.

Different Types of Replacement Windows

Installing replacement windows

Replacement windows, sometimes called pocket windows or insert windows, must be specially ordered and cannot be found on the shelves of home improvement centers like new-construction windows can.

These windows don’t have a nailing flange. Instead, they are designed to be inserted into a finished window opening. You can order replacement windows from your local home center or a few select retailers online.

Common kits for replacement windows include:

  • Sash kits – used to replace deteriorated window sashes without replacing the entire frame or window unit;
  • Insert replacements – used to replace single or multiple window panes. They are designed to fit snugly within an existing frame without making any alterations to the existing structure;
  • Full frame replacement units – replace both the window sash and frame in one kit. This type of window kit includes all the necessary components to install a new window frame and sash;
  • Storm window kits – add additional protection to window openings during inclement weather, providing a layer of insulation and protection. This kit contains everything needed, such as window frames, storm glass, and hardware;
  • Blinds and shades kits – add window treatments, such as shades or blinds, to an existing window frame. These kits usually include the needed mounting hardware and brackets;
  • Window grille kits – Window grille kits include frames and accessories to add decorative grilles to existing windows.

Ensuring the Perfect Fit: Measuring Windows for Replacement

How to install replacement windows

Before installing a window, the most critical step is to measure the existing window frame to ensure that the replacement window you order is the proper size.

Here is how to measure accurately for your replacement windows:

  • Measure the width of the existing window frame from the inside of the jamb at the top, middle, and bottom. Write down the smallest measurement;
  • Then measure the height of the frame in three places: at the left jamb, in the middle, and the right jamb. Starting at the sill’s top, measure to the underside of the head jamb. Record the smallest measurement of the three;
  • To determine if the frame is square, measure the diagonals from corner to corner. If the measurements match, you can rest assured that the frame is square; however, if the frame is out of square by a small amount – for example, 1/4 of an inch or less – the frame can still be replaced and shimmed to fit;
  • On the other hand, if the frame isn’t square, it will look weird, so a full-frame replacement might be warranted, such as custom vinyl windows, etc;
  • Using an angle-measuring tool to determine the sill’s slope for replacement parts.

Removing an Old Window in 6 Steps

Installing windows

Follow these steps to remove existing window frames:

1. Remove Storm Windows

Begin the window removal process by removing storm windows covering the main house window. The storm windows can be unscrewed from the main window frame and then separated.

2. Score the Window Edge

Use a utility knife to score the edges of the old window glass, cutting into the paint around the window to free it from the frame. Move the utility knife along the entire perimeter of the window in one continuous motion.

3. Remove Sash Weights or Springs

If the house window has sash weights or springs, use a flathead screwdriver to pry out them to free the window from its moorings.

4. Identify Stops

Stops are pieces of wood or metal that hold the window in place. Examine the frame around the window and carefully identify each stop.

5. Score and Remove Stops

Using the utility knife, score around each identified stop. This should be done along the entire perimeter of the stop, cutting through the paint. After the stop has been scored, use a flathead screwdriver to pry it out of the frame.

6. Fill Holes and Attach New Pieces for Stability

After all the stops have been removed, holes will be left in the frame where the stops were. Fill the holes with wood putty and allow it to dry. Then, attach new pieces of wood or metal as necessary for added stability.

How to Install a Window in 8 Steps

How to install a new window

How hard is it to install a window? Not too difficult if you follow these steps:

Step 1: Clean and Repair the Window Opening

Use a putty knife and chisel to remove broken or deteriorated mortar joints around the window and clean any debris from the framed opening.

Step 2: Dry Fit the Replacement Window

Insert the replacement window in the opening, ensuring it is level and plumb. Secure the window in place with shims to hold it in place.

Step 3: Install the Replacement Window

Apply an even bead of caulk to the area between the window frame and the opening. Insert the window into the opening and secure it in place with nails.

Step 4: Check the Sashes

Home windows installation

Make sure that the window sashes open and close easily. Check that the locks and other hardware are operational and secure.

Step 5: Trim Off the Shims

Use a dovetail saw, handsaw, or keyhole saw to carefully make your cut along the edge of the shim where it needs to be trimmed. Once you’ve made your cut, use sandpaper or a file to smooth the edges of the cut. This will ensure a tight, professional fit.

Step 6: Fill the Gaps

Fill any gaps between the window frame and the opening with foam insulation.

Step 7: Install Stop Molding

Cut a piece of stop molding to fit the contour of the trimmed opening and attach it firmly to the window frame to form a watertight seal.

Step 8: Install New Window Trim

Cut lengths of molding to fit the contour of the opening and install it around the window frame to finish the job. Apply a bead of caulk along the outside of the trim to form an additional seal.

New Window Installation Tips

Install new windows

Here are some tips for after new window installation:

  • Inspect the windows: Once installed, take some time to inspect them carefully. Look for gaps or cracks around the frame, and ensure the windows are properly sealed. If you see any problems, contact the installer immediately;
  • Run the windows: Once you’re satisfied that the windows are installed correctly, run them through their full range of motion. This will help to ensure that they operate smoothly and don’t stick;
  • Clean the windows: New windows can be dirty, so it’s important to clean them before you use them. Use a mild soap and water solution, and dry the windows thoroughly;
  • Enjoy your new windows!: Once your new windows are installed, you can enjoy the benefits of improved energy efficiency, comfort, and security.

DIY vs. Hiring a Professional Window Installation Company

How to install windows in a house

DIY window installation typically involves purchasing the windows and fitting them into the frame of a building to save you some money. However, when tackling the task of installing windows yourself, you risk damaging your home and losing out on the professional advice and guidance of experienced installers.

Furthermore, improper installation of windows can lead to air leaks, water leakage, and other problems that cost homeowners expensive repair and replacement bills. Hiring a professional window installation company will give you peace of mind that your windows will be installed correctly and by trained professionals.

Professional residential window installation companies possess the necessary tools and knowledge to install your windows correctly and securely. These experienced contractors can also provide guidance and advice on how to customize windows to your needs. Furthermore, they have access to a wider variety of options than a DIY window installation project.

In addition, professional window companies often provide warranties and guarantees on their work, giving you peace of mind that your windows will be installed appropriately and last for many years.

Ultimately, your decision to go with DIY or professional window installation will depend on your experience level and budget. DIY windows can be a cost-effective way to replace windows on a budget, but hiring a professional window installation company may be the best if you want a reliable and secure installation.

The Bottom Line: Hire Professionals Instead

To avoid serious mistakes in window replacement, one needs to study the market and choose the best window company. Installation requires certain skills, knowledge, and professional tools, which is why must be performed by professionals.

Choose Apex Window Werks – a company with years of experience in window replacement projects that will work for your safety and meets your budget. Get a free estimation today.

Nina Tsoy

Nina Tsoy

With over 15 years of experience in the window repair, replacement, and manufacturing business, Nina is in charge for strategic solutions and exceptional operational performance at Apex Window Werks. This allows her to offer innovative techniques and solutions to address any window-related problem, all while adhering to industry standards and best practices.

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