DIY Window Replacement: Your How-to Guide for DIY Window Installation

There are any number of projects you could do around your home — in fact, you probably have a running list pinned to your refrigerator right now. If home window replacement is on that list, you might be wondering if this intimidating-sounding project is something you can tackle yourself. 

We’ve installed over a million windows here at Window Nation, and we’re happy to give you an idea of what it takes to install a window properly. Warning: it’s not a project for a complete DIY beginner. But with a little research, a few hours of work, and some elbow grease, it’s certainly an attainable project. 

New Construction Windows vs. Insert Replacement Windows

Before you start taking a crowbar to your home, we need to provide a little window anatomy lesson. As you can see in the picture below, there are a number of components around your average window that meet the surrounding wall. If you are imagining yourself taking all of those out, then your installation project would be considered a new construction window. Installing new construction windows involves removing the outer case moldings and even getting into your home’s siding in order to attach the nailing fins to the sheathing. 

New construction window replacement is used for remodeling projects, changes to your home’s exterior, or resizing an existing opening. Many professionals prefer to use this type of replacement for all their window replacement jobs. It’s thorough and looks great. Getting the entire unit out of the wall allows our pros to make sure things seal up tightly, and gives us a chance to alert you to any damage in your walls that you should know about. 

As you may suspect, new construction window replacement is a job that we suggest be left to the professionals. The prospect of opening up the side of your home and getting into your walls is serious. If this is the type of replacement you’d like, give us a call and let us take things from here. 

If you’re content to leave the outer frame of your windows intact, and you know they’re in good shape, then you’re looking at a type of window replacement project called an insert replacement window. This type of DIY requires only basic carpentry skills, and is an inexpensive way to replace your windows. 

Replacement or retrofit windows don’t allow you to change the window size or the way the window opens, but you could certainly replace a window that’s cracked. The only drawback to this style of replacement is that your finished window opening may shrink by a few inches. Insert replacement windows often have an additional frame component which will slightly narrow your view. If you have a row of the same-sized windows in your room, you’ll need to decide if this discrepancy is going to drive you crazy. 

To summarize: New construction windows are typically installed by experienced contractors when a home is first built, but as a remodel project they may be appropriate if the studs and/or frame of your window are damaged, you want a new size or style of window, or you’re already planning on redoing the exterior siding of your home. Insert replacement windows are a simpler option, and achievable as a DIY project. They are appropriate if you have a damaged window pane but do not need to change the size or style of the frame.

man in red shirt replacing a window

How to DIY replace windows

Ready to undertake your window replacement? Since this is an intermediate level project, we assume you’ll already have the following tools on hand. If not, factor their cost into your decision to tackle this project. 

Estimated time:

3-6 hours

You’ll need:

  • Screwdriver
  • Flat pry bars
  • Utility knife
  • Screwgun
  • Torpedo level
  • Framing square
  • Hammer
  • Caulk gun
  • Brad Nailer
  • Latex silicone caulk
  • Shims

You may also need:

  • Stop moldings 
  • Trim paint and paintbrushes
  • Miter saw

Step One: Get a quote

It’s always wise to gather a quote from a professional before you start a DIY project. It could be that your project is more affordable than you are imagining. Getting a dollar figure on a home improvement project before you decide to take it on yourself is a smart move. 

options for window glass and trim

Step Two: Measure and Order your Window

Naturally, you’ll need to know exactly what size window you’ll be ordering. Using your measuring tape, measure from the inside of one jamb to the inside of the opposite jamb. You’ll want to get a number for the bottom, middle and top on both the horizontal and vertical axis—three measurements top to bottom, and three measurements left to right. 

You’ll use the smallest measurement for both your vertical and horizontal axis when ordering your new window. If you’re wondering where to buy replacement windows, most home improvement stores can help you out. Once you get your measurements, they’ll talk you through exactly how each manufacturer uses these calculations to choose new windows for your frame. 

Your window measurement is not one to fudge. If your home store doesn’t have what you want on the shelf, you’ll need to make a special order. Don’t despair — spending a few weeks waiting is better than winding up with a drafty window. 

Most window units will come to you slightly undersized to allow for insertion. Emphasis on slight here — too small a window and you’ll experience drafts. 

If you live in an older home and your window is no longer a perfect square, you may need to reach out to a professional on this one. 

woman measuring a window in her house before a construction project

Step Three: Remove the Window Stops 

Your window has arrived, it’s a day with excellent weather, and you’ve set aside a few hours to work. Time to get down to business. Using a pry bar or your putty knife and hammer you’ll carefully pry away the window stop molding from the top and sides of your window frame. 

You may encounter some screws securing that molding in place. You may also find that your molding has been painted into place. Carefully slice through that layer of paint with your utility knife before prying it away from the frame. Work gingerly, as you’ll want to reuse your stop moldings later. If you find those stop moldings are old and brittle, throw them away and install new ones. 

Step Four: Take out the Inner Sash and Parting Stops

Your next step is to carefully remove the inner window sash from the opening. You’ll remove the knotted weight cords that are found in the holes on the sides of the sash frame. Sometimes you’ll find these sash cords are nailed into the sash frames. 

Next you’ll want to remove the parting stops. Using your screwdriver or a small pry bar take out the narrow parting stop moldings that separate the inner window from the outer part of the window sash. It’s precise work, but unlike your stop moldings, you won’t be reusing these later on. No worries if they break. 

Step Five: Remove the Outer Sash 

Once you’ve removed the parting stops, you’ll find that the outer window should slide out easily from the window frame. You can free your window frame from the sash cords by pulling the knots out of their openings on the side of the sash frame. 

Step Six: Remove the Counter Weights and Pulleys 

On the sides of your window frame are the weight pockets. Open those up and extract the heavy weights. Use your utility knife to cut the sash cords and remove them. Take the weight pulleys at the top of the window frame and unscrew them. Dispose of the weights, cords, and pulleys. You’ll need to take those metal weights and pulleys to the recycling center, but the cords can go right into your household trash.

Step Seven: Fill your Weight Pockets with Insulation

The weight pockets will need to be filled with loosely packed fiberglass insulation. This will save you from heat loss, and improve your window’s overall energy efficiency, so don’t skip this step. Once you’ve filled those up, screw the weight pocket covers back into place. 

Step Eight: See How your New Window Fits 

Take your new insert window and fit it into your frame opening. You’ll need to use whatever expansion strip or header that is called for. Loosely shim your new window into place. Take out your carpenter’s square and torpedo level, and continue to adjust the window until it is both level and square.

Step Nine: Make sure your Window is Secure

Once you’ve got the fit right on your new window, you’ll take it out of the opening and set it aside. Next, you’ll apply a layer of caulk to the window frame. Follow your manufacturer’s instructions closely. Once that’s completed, you’ll reinsert your new window onto the caulk. Take another look at your levels with your framing square and torpedo level. Use whatever shims you need to lightly wedge your window into place. 

Give your new window a test open. If your sashes feel too tight, use the adjustment screws in the side channels. If that doesn’t fix things, you might have to try a thinner shim. 

When your window feels like it’s a good fit, with sashes that move easily, your next step is to drive the mounting screws through the side channels into the window frame. This secures the window frame into place. You’ll find drilled openings on your windows that’ll let you know where to drive these screws. Don’t over tighten your screws, or you’ll pull the sash frame out of square and put too much pressure on the window. You can now neaten up any shims that stick out from the sash frame. 

Step Ten: It’s time to Caulk the Joints 

On the top of the window, you’ll take the header piece and slide it up to eliminate any gaps. From here, apply caulk to the joints on the inside and outside of the window. Make sure you follow your manufacturer’s instructions carefully. Some manufacturers approach this step differently, and may require you to leave a gap at the bottom of the sill for drainage. 

person caulking their window

Step Eleven: Install your Window Stops 

You know those window stops you saved from step three? It’s time to reattach those around the sides and top of your new insert window. Use your brad nailer or screws. If you found you needed new stops, or your old ones were damaged during removal, no sweat. Take out your miter saw and cut a new set. You’ll want to paint or stain them before you install.

Step Twelve: Final Caulking and Painting 

Your last step in this process is to caulk the joints around your stop moldings. If you need some final touch-up paint, now is the time. Clean up and look forward to your well-earned bragging rights. 

person paints window sill with white paint

What are the pros and cons of DIY window replacement?


Most homeowners are well aware of the cost savings when looking into DIY home improvement projects, but there are other benefits to keep in mind as well.

Save money on labor costs

When you take on a project yourself, you only have to foot the bill for materials. According to The Construction Labor Market Analyzer, the labor cost on most home improvement projects works out to be around 20-40% of the total costs.

While you’ll save money on labor when you do it yourself, you may end up paying more for your materials. Most professional window companies buy their windows in large quantities direct from the manufacturer. When construction materials are sold to the consumer however, they often come with a markup. 

When you are budgeting for this project, always be sure to calculate what your material costs are going to be, the hours you’ll spend on the project, and what your time is worth. 

Learn a new skill

Every new DIY project you tackle makes the next project a little easier. The first time you replace a window, plan on it taking you between four to six hours. Once you learn how to replace home windows, it’ll get easier for the next time, and the skills you learn on this project should transfer to other household carpentry jobs. 

Become a more self-sufficient homeowner

It feels great to have sweat equity invested in your home. We all want our homes to reflect our personalities, and there’s an extra level of pride in knowing that you were able to maintain your home yourself.


It’s important to be realistic when you enter into any DIY project. Consider the below list before you commit to replacing your home windows yourself. 

Risk of injury

If you live in a home that was built before 1978, you may have lead paint. Before you disturb any painted surface in your home, make sure you know what you are dealing with. You can purchase home lead testing kits at most hardware stores, or reach out to your public health department on how to collect samples and where to have them analyzed. 

You’ll forfeit warranty protections

Each window we install at Window Nation has a twenty-point installation review, and our teams of professional installers bring an average of sixteen years experience to the work. Depending on your window, that professional installation will be backed up by a warranty for anywhere from one year to a lifetime. A little money spent upfront on labor pays off in the long term with strong warranty protection.

Unprofessional installation dangers

Somewhere down the line, you may decide to put your home on the market.  Put yourself in the shoes of a prospective home buyer. If you were purchasing from a DIY-er you didn’t know, it might give you pause. 

Experts estimate that nearly 40% of the average family’s heating and cooling costs can be attributed to drafty windows. Improperly installed windows can lead to leaks and drafts, making your home less comfortable and costing you more money every month in utility bills.

It’s also important to consider that a professional window installer gets a good chance to look inside the walls around your window and identify decay or water damage. They know what to look for, and can help you prevent costly repairs down the line. 

When should I get professional window installation help? 

If you’ve done your due diligence, gotten a quote, done the cost-benefit analysis, and consider yourself a fairly experienced DIY-er, window installation should be no big deal. That said, you may want to consider professional installation if you:  

  • Suspect your home has lead paint
  • Want to change the shape or size of your window
  • Want to alter the style or the way your window opens
  • Suspect your window frame has water or termite damage
  • Want your windows to have a uniform appearance 
  • Are concerned with energy efficiency
  • Are considering selling sometime soon
  • Have little or no DIY experience

two professionals replacing a window in ahome

Are you up for it?

Replacing your home windows is not the easiest or quickest DIY project out there. That’s why it’s always smart to request a free quote from Window Nation before you begin. Our team of professional window specialists are ready to give your home the sprucing-up it needs — no matter how complicated the installation.

ARTICLES You May Also like

Get started on your home improvement project with these helpful resources.

Sponsor Free Zip Codes | Buy 2 Windows, Get 2 Free | 0 Down 0 Payments 0% Interest for 2 years! Details »