These directions summarize some supplies and steps we have found helpful when working with windows. This information is offered for use at your own discretion, and it may or may not be applicable to your specific project. Please consult a professional for more detailed advice regarding your project.

Kinds of Windows

  • sliding – pane moves to the left or right, often found in bedrooms
  • fixed – doesn’t open, just used for light and decoration
  • single-hung – two sections, bottom section opens by sliding upward or popping open, easy to clean
  • double-hung – two sections, can open from the top or bottom, moving up or down
  • casement – hinged at the side, rolls open, often used for living rooms
  • awning – hinged at the top, pops open at the bottom, to the outside, can stay open during a light rain without the room getting wet
  • hopper – hinged at the bottom, pops open into the house


  • measures thermal resistance, energy efficiency
  • windows are rated between 0-6
  • the higher the number the better, the more energy efficient
  • standard window is usually .88
  • energy star rating is 2.9
  • typical double pane window is about 2

Parts of a Window

  • casing – decorative framing of a window
  • stops – the foot that holds in the edges of the window
  • flange – external lip of the window, provides support and sealing
  • pane – the glass in a window
  • sash – the flat piece of the window that goes inside the frame
  • sill – the bottom part of the window that sticks out from the wall
  • apron – the piece below the sill at the bottom of the window


  • pencil
  • tape measure
  • utility knife
  • Vycor – a sticky tar paper, used for weatherproofing
  • shim – a small, flat or wedge-shaped piece of wood or other material, used to stick into excess space and make a window level
  • electrical drill
  • 1” – 1 ½”screws (often for aluminum windows with flanges)
  • Number 8 nails for a hammer (often for wood windows)
  • 16-guage nails for a nail gun (often for wood windows)
  • nail gun
  • pry bar
  • mini pry bar
  • sawzall (can use other kinds of saws, but the work will take much longer)
  • expansion foam
  • water-based caulking (easier to clean up and can be painted on)
  • silicone caulking (can use when it’s wet, so it’s good for skylights or chimneys and times you’re working in the rain)
  • caulking gun
  • flashing – a piece of metal or plastic that goes above the window to help shield out water


Removing the Old Window

  1. Using a pry bar and a hammer, remove the siding of the house around the window
    1. Hammer lightly underneath the siding and pry toward yourself
    2. Start with the lowest piece of siding and move upward
    3. Siding is very easy to break. If you can’t pull it up without breaking the piece, you may just have to replace it later
    4. If the house has stucco instead of siding, use a diamond blade on an angle grinder. Cut along the edge of window. Wear a protective mask and know the project will take more time
    5. If at any point, during any step, you worry about the window breaking, feel free to tape the glass
  2.  If the window has casing, remove that, too, with a pry bar
  3.  Feel where the window’s flange protrudes from the house, and cut right alongside it with a utility knife, breaking up any caulking
  4.  From the outside of the house, take out the screws from the window
    1. Take the screws out from the bottom to the top
    2. If the window uses nails, cut around it with your sawzall. This will cut right through the nails and release the window
  5.  Start wiggling the window out from the bottom corners
    1. If the window doesn’t release, figure out where it’s stuck and which connection points are hindering the process. You may need to take your knife to the caulking again or remove another screw
  6.  Set the window aside in a place where you will not kick it or trip over it
  7.  Assess the window’s hole for damage
    1. If you see mold that you can easily scrape away, scrape it away
    2. If you see mold that is larger, spray it with bleach water (half bleach, half water). You can continue your project whenever the solution is dry.
    3. If there is substantial rotting, you will have to replace the structure of the hole. Be sure to address why the rotting occurred, and avoid that in your new window
    4. If the underlying paper is torn or heavily worn, put new Vycor over it. Don’t try to pull up or remove the old paper
    5. And if there are any nails sticking up, hammer them back down

Installing the New Window

  1. Assess the size of the new window, as compared to the old one
    1. It’s very common for windows to morph over time, so it’s extremely important to measure windows carefully. Houses, also, are oftentimes not level
    2. Measure each side of the window, but also measure from corner to corner, in an x. The measurements should not include the flange
      1. If the new window is the same size or less than ½” smaller than your old one (on all sides), you will not need to adjust the size of the hole. This is the ideal situation for a do-it-yourselfer
      2. If the new window is more than ½” smaller than the old one, you will need to shrink the hole. This is the next best option for a do-it-yourselfer
        1. Carefully measure your new window and the hole, to figure out how much to fill the space
        2. Find lumber or plywood of the appropriate size
        3. Nail or screw the measured wood into the solid wood of the window’s hole, creating a new hole that is the correct size for your new window
      3. If the new window is larger than the old one, you will need to increase the size of the hole. This is fairly complicated for most do-it-yourselfers
        1. The process involves removing your dry wall, looking at the framing of the house, figuring out whether the wall is load-bearing, taking steps to support the house, making sure you will not interfere with plumbing, making sure you will not accidently cut through wiring, etc. Each home and room is different
      4. To keep it as a simple, do-it-yourself project, avoid larger windows
  2.  Push the new window into the space for a general fit
    1. You should be able to wiggle it around slightly
    2. About ¼” gap on all sides is a good amount of space to leave
  3.  Then wedge in your shims to give it a snug fit
    1. You can use two shims in one spot, if necessary. Don’t force-fit them
    2. Make sure the window is not protruding too far out or sunken too far in
    3. The windowsill will serve as a good guide for placement. It should be level in all directions
    4. Leave a gap at the top of the window up to 1 ½”. This will allow the window to breathe and expand when it’s warmer
  4.  Screw/Nail in the sides of the window
    1. There should be small holes in the flange for the screws (two or three on each side). You do not want to create new holes
    2. Start at the bottom and work your way up
    3. If the window is wooden, hammer the nails into the side of the house from the inside of the window (about four on each side)
    4. You don’t need screws or nails on the top or bottom of the window
  5.  Put Vycor over the screws and flanges around the window
    1. Start at the top and pull the tape downward
    2. Do the sides first, then the top. Don’t put Vycor on the bottom, in order to allow for run-off
    3. Press it down firmly, starting from the middle and working in each direction
    4. Try to avoid creating bubbles, and get rid of them when you can
  6.  If you want flashing, place it above the window prior to putting on the casing
    1. Flashing should protrude about ¼”
  7.  Screw the casing over the flange
    1. Measure where the flange will be underneath the casing, and screw the casing outside of this area, in order to avoid making new holes in the flange
  8.  Put expansion foam into the gaps around all the sides of the window and at connection points between the casing
    1. Shake well before use
    2. Use a very light bead, as the foam will expand. If you use too much, you will accidentally compress the window
    3. Hold the can upside down for best effects
    4. Consider wearing gloves, as the foam is extremely sticky
    5. You can also use caulking, as another option
    6. Bear in mind that caulking may shrink when it dries
    7. Taping the window can leave a very clean finish with caulking. For the cleanest line, remove the tape right after the caulking is on (it doesn’t have to be dry), and pull in the opposite direction of the caulking
  9.  When the expansion foam is dry, cut off the excess foam that is not within a gap, with a utility knife
    1. Expansion foam takes roughly three hours to dry, but see the can for drying directions
  10.  Put the siding back on the house, around the window