Thinking about replacing your windows? One of the first things you’re probably wondering is what exactly the process looks like – and whether you can do it yourself. While DIY window installation is possible, many homeowners face unexpected challenges. On the other hand, a professional window installer brings years of experience. They know how to handle surprises like rotted frames, structural issues, or out-of-square openings that often pop up during replacement window installation.
Before you decide, you need a better idea of how windows are replaced and whether you want to take it on as a DIY project. That’s why we put together this detailed, step-by-step guide for the window replacement process.
Is It Time to Replace the Windows in Your House?
First things first: Do you even need to replace your windows? Chances are, they’re letting you know if it’s time. Watch for these common signs that it’s time to replace your windows:
- You feel drafts or cold spots near your windows
- Your energy bills keep going up
- You see condensation or fog between glass panes
- Windows stick, squeak, or won't stay open
- You notice cracked glass or damaged frames
- Water leaks in around the frame during rain
- Your windows look worn or outdated
A professional window company can spot problems you might miss and help you decide if replacement windows are worth it. They'll check the frames, glass, seals, and operation to tell you which windows need replacement first.
Replacing Windows: Things to Do First
Before you start replacing windows in a house, you'll need a clear plan and the right products. A professional can guide you through important decisions about styles, materials, and features before you even begin the window replacement process.
Find a Trusted Window Installation Company
Start your project by finding a window company with solid experience and good reviews. A qualified dealer will visit your home, explain different window styles, frame materials, glass types, and other features, and help you pick options that match your needs and budget. Working with a pro from the start helps you avoid common pitfalls like ordering the wrong size or choosing windows that don't meet local building codes.
Assess Your Needs
Take time to think about which windows need replacement and why you want to replace them. Could you make repairs on some windows while replacing others? Do you want to replace many windows at once to save money and get a consistent look, or tackle the window replacement process in phases to spread out the cost? A window pro can help you weigh these factors and create a replacement plan that fits your goals and budget.
Choose Your Operating Style
To choose the right style, consider how each window gets used and where it’s placed. Will you open it for fresh air or keep it closed to block noise? Over-the-sink kitchen windows work best with easy-to-reach cranks, basement windows are small and secure, while living areas and bedrooms need windows that meet egress rules.
You also don't have to stick with the same style you have now. For example, you could swap a picture window for a sliding window to add ventilation or replace single hung with double hung windows for easier cleaning. You can even combine window types – like adding awning or slider windows below picture windows to let in fresh air. A professional can help you choose the right window for each room.
Find the Right Frame
Your window frame material affects both how your windows look and how they perform. Vinyl frames offer great value and require almost no maintenance – you'll never need to paint or refinish them. Aluminum frames have slim profiles that work well in modern homes and stand up to tough weather. Then there's fiberglass frames, which combine the strength of aluminum with excellent insulation properties.
Beyond the material itself, you'll also need to pick a frame color that matches your home's style. While white remains popular, many homeowners now choose black frames for a bold look or wood-grain finishes that add warmth. Installing replacement windows is your chance to really customize your home.
Pick the Perfect Glass
Glass options can make a big difference in your home's comfort and energy bills. For energy-efficient windows, choose Low-E coatings and double- or triple-paned glass with gas fills. For bathrooms or street-facing windows, obscure glass patterns provide privacy without blocking natural light. And if you live in a storm-prone area, impact-resistant glass can protect your home from flying debris and break-ins.
Finish with Window Grids
Window grids can match your personal style and add character to your home. Traditional homes often look best with colonial grids that divide each window into even squares, while Craftsman-style and prairie homes typically feature grids only at the top of windows. You don't have to add grids to every window either – many homeowners leave some windows grid-free for clearer views.
Measure Your Windows
Proper measurement is the most important part of preparing for the window replacement process. Even being off by a quarter inch could mean your new windows won't fit or work properly. Professionals measure each opening at several points, check for square corners and level sills that could affect installation, and look for hidden problems like water damage or rotted wood that could complicate your project.
Order Your Windows
After all the careful planning and measuring, ordering your windows might seem simple, but there's still a lot to coordinate. Each window needs the right combination of size, style, frame material, glass package, color, and optional features, and delivery timing affects when installation can start. Professionals handle these logistics regularly and can make sure your order is correct and arrives together to avoid delays.
Replacement Window Installation: Step-by-Step Process
The window replacement process varies slightly based on the type: pocket replacement or full-frame replacement. Pocket replacement keeps your existing frame and just swaps out the window itself. Full-frame replacement removes everything down to the rough opening in your wall. We’ll give a step-by-step process for a full-frame replacement because it also includes what to do for a pocket replacement.
Step 1: Remove the Sash
The sash is the part of your window that holds the glass in place. To remove it, score along the edges with a utility knife to break any paint seal. Remove any exposed screws with a screwdriver. Then, gently work a putty knife or pry bar between the frame and sash to loosen it and remove it from the opening. In older windows, you may also need to remove the wood stops that hold the sash in place.
Step 2: Remove the Frame
For full-frame replacement, the entire window frame comes out of the wall. Start by cutting through the caulk around the frame with your utility knife and removing any nails securing the frame to the rough opening. Next, take a pry bar and work it between the frame and the opening, starting at the corners. Work your way around the frame, pulling it away bit by bit. Keep in mind that full-frame replacement requires careful work to protect your home's siding and interior walls, and is best left to a professional.
Step 3: Prepare the Opening
Before installing replacement windows, clean and inspect the rough opening. Use a putty knife and wire brush to scrape away old caulk, paint, and debris, and pull out any remaining nails or screws. If you didn’t already remove the frame, check it for signs of rot or water damage: soft, discolored, or crumbly wood needs to be replaced. Finally, vacuum the area clean and wipe down all surfaces.
Step 4: Install the New Frame
If you removed the frame, you’ll need to install a new one. Position your new frame in the rough opening, making sure it sits level (exactly parallel to the ground) and plumb (exactly perpendicular to the ground). Check your measurements with a level tool on all sides. Once the frame sits correctly, secure it with screws through pre-drilled holes. (Don't overtighten the screws, as this can warp the frame.) Apply flashing tape around the exterior to prevent water leaks.
Step 5: Check That the Sill Is Level
If you only removed the window sash and the frame remains in place, you still need to check that the sill – the bottom part of the window frame – is perfectly level. Installers use a level tool to check this crucial measurement. If needed, they'll add shims under the frame to correct any slope. Even a slight tilt can affect how your window opens and closes.
Step 6: Insert the Replacement Window
Now you're ready to begin the actual window replacement process. First, do a dry fit: Place your new window in the opening without any caulk to make sure it fits properly and that you have about a quarter inch of space around all sides of the window. Once you're satisfied, remove the window and apply a continuous bead of exterior-grade caulk around the frame where it will contact the opening. Carefully set the window back into place and center it in the opening.
Step 7: Fit the Window Properly
A properly fitted window should be plumb (straight up and down), level (horizontal), and square (equal diagonal measurements). Insert shims at the bottom corners and at 12-inch intervals along the sides to adjust the window's position. Don't force the shims - they should slide in with light pressure. Test the window by opening, closing, and locking it several times.
Step 8: Insulate and Seal
Fill the gaps between the window and frame with insulation. Be careful not to overfill, because expanding foam can bow your frame. Once the insulation is in place, apply exterior caulk around the outside of the window where it meets the siding. Inside, run a bead of paintable caulk around the window where it meets the wall. This is one of the most important parts of the replacement window installation process.
Step 9: Install Window Trim
Interior and exterior trim covers any gaps, insulation, and caulk and makes your windows look finished. For interior trim, apply construction adhesive to the back of the trim, press it into place, and secure it with finish nails every 12 inches. For exterior trim, cut the pieces slightly longer than needed and angle-cut the ends for proper water drainage. Caulk all joints and nail holes, then paint or stain the trim to match your home.
What to Expect When Replacing Windows: Your Questions Answered
When you're planning for window installation, you probably have lots of questions about what to expect. Here are the answers to the questions about the window replacement process we hear most often from homeowners like you.
Does Window Replacement Include Trim?
Most window companies include basic trim work in their installation, with options to upgrade to wider trim or decorative options. Ask your installer about trim options before work begins. They should explain what comes standard and what costs extra.
How Long Does It Take to Replace a Window?
The replacement window installation process typically takes 30–60 minutes per window for basic projects. Full-frame replacements might take 2–3 hours each. Weather, unexpected repairs, custom work, and cleanup can add more time. Your installer should give you a timeline before starting work.
How Are Replacement Windows Installed?
Installers follow careful steps and use special tools to remove old windows and install new ones properly. For example, they’ll need to pry out the old window sash without damaging your home, use shims to ensure proper fit, and clean up afterward. Good installers will explain the window replacement process and answer your questions.
Leave the Replacement Window Process to the Pros
Now you know how to install replacement windows – but should you do it yourself? The window replacement process involves many steps and decisions that affect your home's comfort, value, and appearance, and professional installers know how to handle it all. To see the value of a professional for yourself, contact a MILGARD Certified Dealer today. They'll guide you through the entire process from selection to installation and make sure your windows work properly for years to come.
