Much double hung window repair is not especially difficult. It is usually well within the capabilities of a reasonably handy homeowner. This article will take a quick look at sash repair in particular, which is one of the most common repair and maintenance procedures required. With some basic tools and a minimum of double hung parts, this repair can be done fairly quickly and easily. There are a number of other similar double hung window repair projects that can be taken care of with similar ease, but this will give the reader an idea of the difficulty level involved in double hung window repair.
The traditional way to set up double hung windows in the late 19th and early 20th centuries was to have chords that attached to the sashes (the parts of the window with the panes and which slide up and down) on one side and on the other to weights concealed in open spaces behind the window jambs (the side surfaces). At the tops of the windows are pulleys in which the rope sits and allows the pulley action to work. The entire assemblage is intended to make the sashes easier to raise and lower.
A common problem requiring double hung window repair is that the sash chords become old and corroded. This makes the rope susceptible to breaking. This can be dangerous as nothing will be counterbalancing the window and it can come crashing down, breaking the window or landing on top of fingers. So a common and fairly simple repair is replacing the sash chords. Since this is a short article we won't necessarily have time to go over all the definitions of terms, but you can look them up very easily. For this repair as far as double hung parts go you should only need a roll of new 1/4 thick nylon cord or other strong rope:
Once you've taken out the stop bead and parting strips the sashes are free to move, but you will see they are attached to chords, so cut the bottom sash chords and remove the sashes. Be a bit careful though, suspended weights are attached to these chords and they will probably fall down into the compartments behind the jambs with a plunk. These counter weights are some of the heaviest double hung parts so use an ordinary amount of caution. If you try to hold onto these chords, they can pull your fingers up toward and into the pulley, so don't. Just cut the rope and let the weights fall.
In the jambs of these windows you'll see access panels - little rectangular pieces of wood that can be taken out. Take them out and you will find compartments. The weights that you have cut loose will have fallen into these compartments. Take them out so you can tie new cord to them.
Spray the pulleys with some penetrating oil (WD 40, etc.) to lubricate them.
Tie new nylon cord to the weights
Tie new pieces of nylon cord to the weights. You will want to do this by putting chord through the pulleys on top, down into the cavity, and out. So you will need fairly long pieces of rope. It may be easier to use a whole roll of rope and cut it later. There are pulleys in both sash tracks - front and rear. Fish the new nylon cord through both of them in the same down and out way. Tie the chords to both sets of weights with strong knots that won't come loose. Place them back in the cavity.
Suspend weights and fasten cords to sashes
To reattach the bottom sash, pull on the new rope so it rolls in the pulley and becomes taught. Pull it some more so that the weight attached to the bottom sash comes up to a height of about 8 inches above the sill level. Now measure down the part of the cord on the exterior to about the length of the groove in the sash (as it sits at sill level) and add about 3 to 5 inches (for the knot). Cut the chord there. Tie a large not that fits into the sash groove hole tightly. Place it in the sash groove/hole and drive a nail through it to hold it in place.
For the top sash you will do about the same thing, except that the weight hangs at about 4 inches above sill level, and the cord is measured out to fit into the sash groove and hole when it is up flush with the header.
Replace the sashes, parting strip, and stop bead
This is all fairly self explanatory. You may need to pull the finish nails out of the parting strip and stop beads but sometimes you can just tap the same nails back in. If you do choose to pull them out, you'll need new finish nails with which to nail them back in.
When you're finished you'll have nice strong new nylon cord or other strong rope suspending the two sets of weights (four weights total) and lubricated pulleys to make sure they move up and down smoothly. Check every few years for wear and tear on these cords and replace as necessary. This is an example of a double hung window repair project, and as you can see, though it requires careful attention, it is quite feasible with basic tools and know how.