Wednesday, July 4, 2012

I had hinted about a post on replacing double-hung windows, and Copperhead is holding me to it.

 This is the last window to be replaced on the house, the smallest (28" wide x 34" high--the others were either 36"x46" or 40"x54") and in the best shape.  This window is in the first floor bathroom, and faces north.  The windows on the east, west and south were missing glazing compound, missing ropes, had broken glass, and storm window issues on more than half of them--missing glass and even missing wood.

Another factor on replacing the windows rather than repairing them is the matter of the sash weight pockets.  These amount to a 2" wide strip down each side of each window for the sash ropes and weights to operate in.  This comes out to four inches by four to five feet of uninsulated wall for each window, multiplied by sixteen windows makes about a five-foot square hole in your insulation.  These wood windows also had no weatherstripping at all.  They were a tighter fit in the frames than some of the windows I have worked on from the early 1900s, but still not tight enough in these days of expensive energy.

Another factor was the lead paint issue.  There has been a lot of noise and heat on that subject, but not really much light.  Not all houses are equally hazardous in this respect.  While using lead compounds in paint was not officially banned until 1978, the paint companies began using other pigments during World War II, because lead was needed for the war effort (my source on this was an old friend who worked as a paint chemist for a regional paint manufacturer).  So it is less likely that this house, built around 1950, has as much lead-based paint that would be found on on a home built in the late 1800s or early 1900s.  But if there is lead paint, it will be on woodwork and exterior wood, not on plaster or drywall.  And the primary risk is not paint chips, which if swallowed will likely pass through undigested, but from paint dust generated by painted wood parts rubbing against each other--a window in its frame or a door that rubs on its jamb.  Replacing the windows removes that possible source, if they should have lead-based paint under the later coats accumulated through the years.

It does not take a lot of tools to handle this job.  I think I left my small handsaw out of this picture, but I could get by without it by using the chisel.

The first step, before getting the replacement window, is measuring.  Open the window, and get the closest measurement you can from side to side in the track the window slides in, and then from top to bottom. If the case of the tape measure will not fit inside the track, measure to the joint between the inside stop molding and the window frame.  Once you have these measurements, you will need a replacement window half and inch narrower and a quarter of an inch shorter than the measurements of the opening. 

When you have the window, there is one more issue to think about--do you need a helper to handle the units with you?  This particular window is small; I could handle it alone.  I also did the rest of the windows alone.  But I have done window replacements for years, since the late '80s.  I will admit the first floor windows were about as big as I am willing to handle alone;  for larger windows I would prefer to have another person.  Double-pane glass is heavy, and expensive if it breaks.  The windows I installed in the second floor were marked as weighing 44 pounds, the larger ones for the first floor were about 54 pounds each.  This window was only about 20-25 pounds.


Now, we have the properly sized replacement unit on hand, and are ready to remove the old window sashes.  This house was built toward the end of the use of wood double-hungs with sash weights, but these old windows are not much different from those used 100-200 years ago.  The first thing to come out is the stop molding, shaped pieces of trim that surround the top and sides of the sash channels.  Find the joint between molding and frame, and carefully use a small pry bar to pull it off.  It may help at the start to use a knife to cut any paint on the junction.  Again, pry gently; old wood may be dried out and can break more easily.

Once the moldings are out on all three sides, lift the lower, inside sash and pull one side out of the frame.  Then look for the groove in the side of the sash where the rope is strung.  Usually the rope is secured at the end of the groove by a knot; sometimes someone has put a nail through the knot.  Pull the knot out, ease the rope up until the sash weight bottoms out in its pocket in the wall, pull the sash the rest of the way out and remove the other rope.  Set the sash out of the way until you dispose of it.  Note:  some windows may have been converted to a small chain rather than rope, which can deteriorate and break after many years.  This chain will be either nailed or screwed into the end of the groove, but otherwise it works the same way.

Next, you must remove the "parting strip" between the two sashes.  It is a small strip of wood, usually 1/2" by 3/4" fitted into a groove in the frame to separate the two sashes.  Again, it will be on the top and both sides.  A chisel may help to get it started coming out of the groove, then the pry bar to get it free.  Sometimes it is easiest to break it just below the upper sash, lower the sash past the broken end, and then pry out the rest.  (If you are removing the sash to repair the window, either replacing glass or glazing compound, you will have to work harder to get it out intact because you will have to put it back in later.])

Once the upper sash is out and put aside with the lower, remove the rest of the parting strips from the frame[.  The last piece that defines the channels for the sashes is called a "blind stop" and it is left to hold the new window in place.

We still have to deal with the sash weights and ropes, and the pulleys sticking out of the frame near the top of the window.  On the lower part of each side, formerly covered by the lower sash, will be a wood access cover for the sash pockets.  On older windows this is often loose in the frame, and can be popped out.  On the windows in this house, they were cut vertically at each side, but cut only halfway through, unless someone had pulled it out to repair the window in the past (maybe one or two windows in the whole house).  I had to use the pry bar and break these out.

Then I cut the knots off the sash ropes, reached in and pulled out the cast iron sash weights[077], then pulled the ropes out of the pulleys.  The pulley assemblies are mortised into the wood and have screws at the top and bottom.  Often the screws have been painted, and it is necessary to use a sharp knife to get enough paint out to get the screwdriver into the slot and remove the screws.

Put the pocket covers back into their places, and the window is removed.  Cleaning up any dirt, dust or debris is next, and we are ready for the new window.


  1. Nice work...both on the window and on reporting it here on the blog!!

  2. Undoubtedly, the first things to prepare in replacing windows are your tools. Then, you have to take measurements. The smallest measurements are used so your replacement windows fit within the opening. Avoid doing the task alone to prevent incurring injuries and or damaging the materials.

    Tameka Lauricella

  3. Thanks for this post! It’s very helpful for every DIY-ers. =) It must be really tough to do window replacements. What do you suggest for a window pane material? I might try doing your instructions with my friend. I really feel like my living room window needs a replacement. Please keep us posted!
    Kermit Lukacs

  4. Just by reading this blog post, I can tell that you're an expert when it comes to replacing windows and other DIY jobs for that matter. You even know the alternatives you can use if ever you don't have the certain tools to use in this kind of project. I wish you're house is just within reach, so I'll be able to ask you if I need help. Hehe!

    Allyson Ripple