Home > How To > How to install replacement windows in 5 easy steps

How do you install replacement windows? That’s probably why you’re here. Installing replacement windows is not an easy task to do. But if you’re someone who’s willing to give it a try then why not! In this article you’re going to learn 5 easy steps to install or replace windows. From checking, measuring, removing, and installing, you can learn all these things here.

Step 1

The first step is very simple! It is to prepare all the things you will need to install your replacement windows. Firstly, you need to prepare yourself with safety glasses or goggles, work gloves, hearing protection, and lastly a dust mask (this is optional but also advisable). Of course, protection is number one. Below is a list of the tools and materials you will need to perform the project.


  • Cordless drill/Driver and bits
  • Caulk gun
  • Utility knife
  • Level
  • Tape measure
  • Hammer
  • Flat pry bar
  • Putty knife


  • Acrylic caulk / Silicone caulk / Paintable latex caulk
  • Insulation
  • Shims
  • Nails
  • Foam backer rod
  • Fiberglass insulation
  • Wood filler
  • Wood glue
  • Spray foam insulation

These are the things you will need to start working on the installation. Once you’ve prepared all of these you’re ready to start working.

Step 2

You can save time and money by installing your replacement windows yourself. If you have the basic tools and skills then you can do it on your own and save yourself hundreds of dollars in installation charges (just for each window). What’s also great is that new vinyl replacement windows are low maintenance and offer energy-efficient features because of their insulating properties. After you install them they’ll operate smoothly in the years to come.

Now before you start working on the window you need to check the condition of your window frame. If they are rotten or badly out of shape the whole unit including the frame may need replacing. This is a much more complicated job and you will need help from a professional.

You have three choices for your vinyl replacement windows: full frame replacement windows, insert replacement windows, and sash replacement kits.

Full frame replacement windows

This option takes down the entire window frame that includes the head jamb, side jambs, and sill. This is the only option when your old window frame has rotted or deteriorated. This is a more advanced method because you have to strip down the window opening to its rough framing. Including the interior and exterior trims and sometimes the siding.

Insert replacement windows

Sometimes known as pocket replacement windows, this method only replaces the current sashes with smaller windows. It consists of a fully assembled window in a ready-to-install secondary frame. To also do this, your existing window frame must be in good condition. This is also a more DIY-friendly choice because your current trims and siding don’t need to be removed.

Sash Replacement Kits

This choice gives an old window frame new movable parts including jamb liners and a sash. Now that we have this covered, let’s move on to measuring for the replacement window.

Step 3

This is probably the most important step in the window replacement process. It’s when you measure the dimensions of the existing window frame to make sure you order a replacement unit that’s the right size. The first thing you need to do is bring out your tape measure. Measure the inside width of the old window frame jamb to jamb. Measure in the three places. First the top then middle, and finally the bottom. Use the smallest measurement out of the three. The next is to measure the height. When measuring the frame’s height you need to start from the top of the sill to the underside of the head jamb in three places. Start with the left jamb, middle, and the right. Again, use the smallest measurement out of the three. You should use the smallest height and width measurements when ordering your new replacement windows.

You can also check the squareness of the window frame by measuring the diagonals from corner to corner. The two dimensions should be the same. If the frame is out of square by 1/4 inch or so don’t worry. The replacement window can be shimmed to fit. Anything more may require adjustments to the frame. If the frame is so irregular that a square replacement wouldn’t look right, then you’ll need a full-frame replacement. Before you order the new window¬† you should know that the price will vary depending on the manufacturer and the features you request. Once you’ve ordered them, make sure to re-measure them to make sure they’ll fit into the window frame.

Step 4

After the measurement process now it’s time to remove the old windows from the window frame. First thing to do is to remove the sash. You need to pry off or unscrew the inside stop to remove the lower window sash. Remove them carefully since you will be reusing them. Again, carefully because they also break easily.¬† The next thing to do is to use a utility knife and take out the parting stops between the sashes to remove the top sash. If your windows were fitted with sash replacement kits there won’t be any beads. You just simply press on the jamb liners and pull the top of the sash forward. Now you should pry off the jamb liners using the flat pry bar to pry them free. If it is an original window, remove the remaining wooden stops from the frame. Leave the interior and exterior casings intact.

Sash springs and sash weights

If your window has sash springs carefully remove them and raise the sash near the top of the window. If the springs have plastic covers carefully cut and remove them. You need to also remove the screws holding the springs in place. If you’re dealing with sash weights remove them from their pockets and cut the cord pulleys. Let the weight fall inside the frame and stuff the weight pockets with fiberglass insulation. Now it’s time to fill the holes with wood filler and make sure you have solid wood where you’ll screw the new window into the frame for stability. If the wood is damaged or rotten remove it and cut new wood pieces to replace it. Attach new wood pieces using screws and wood glue.

Step 5

The final step is to install the new replacement windows. This is a very delicate process so make sure to prepare yourself. The first thing to do is to clean the window opening. You can also use a vacuum to remove any dust or dirt. Make sure that the sill is level. If necessary use the shims to make the sill level. Ensure they’re placed correctly for proper leveling. Once that’s done, now it’s time to bring out your caulk gun and caulk. It can either be silicon, acrylic, or paintable latex. Apply continuous beads of caulk using the caulk gun on the exposed inner face of the exterior casings. Then do the blind stops on the top and sides of the frame and the sill.

Reinstall the old inside stop. Place the window in the opening. Set the bottom of the insert replacement onto the sill then tip it up into the opening. Rest it against the interior stops and press it firmly against the caulk. Use the shims to secure the window from the inside and drive the screws into the holes and through the shims.

Hold the window in place with one 2-inch screw driven loosely through the upper side jamb and into the framing. The screw should be in just far enough to allow the window to operate. Check that the sashes sit evenly in the frame. Check if your window is evenly placed. Cut the shims that are sticking out. From the outside, apply spray foam insulation recommended for windows into the gaps around the window. Don’t overfill the gaps. On the inside, fill the gaps with minimal expanding foam.

Reinstall the new stops or old ones (depends on you). At the bottom of the adapter, drill two weep holes and lock it onto the window. Apply latex caulk around the interior trim and then prime the interior of the window sash and frame. Once that’s all done, you’re good to go!

Now you know how to install a new replacement window without having to hire someone to do it. You can save a lot! But also consider asking for professional help if you ever find the job too complicated. At times like these, it’s always good to learn one or two new skills. Replacing new windows is one skill that’s worth it. Review the guide above to see a detailed explanation on how to install replacement windows in 5 easy steps. It’s free to read, so you might want to save this and read it again. Maybe you’ll learn a thing or two that will save you money. For hard jobs hiring someone is ideal. For easier jobs you can do it yourself. All it needs is some basic knowledge and skill to start the process.

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