Refurbishing Old Double-Hung Windows – Part One
Windows built 50 to 100 years ago often were constructed from fine-grained, rot-resistant fir, cypress, or redwood, woods that are no longer available. For that reason alone, it makes sense to refurbish rather than replace them when they get tired and don’t work so well.
Refurbishing double-hung windows can be complex, so we’ll divide the topic into two postings. In this first installment, we’ll focus on correctly sizing sash weights, replacing sash cords, and lubricating pulleys. In Part Two we will see what to do if sashes are swollen or out of square, lack weatherstripping or have built-up paint.
The photos above show how the pros at Wooden Window refurbish double-hungs, so we’ll let them do the talking. To undertake this task, however, here are a few common sense suggestions to supplement the techniques shown in the photo sequence.
Dress for the job
Sturdy gloves with rubberized palms are essential to avoid cuts and to provide a secure grip on heavy window sashes. Safety glasses with wraparound lenses will protect your eyes from glass shards, irritating dust and dangerous projectiles should a power tool strike a hidden nail or screw. As older windows often contain lead-based paint, a HEPA-rated respirator and a HEPA vacuum to capture dust are must-haves.
It might make sense, say, to remove and repair all sashes at the same time, but only if you’ve carefully noted the location of all trim pieces and sashes beforehand. Also, if there are people in residence, move cutting and sanding operations outside whenever possible, lay tarps to protect finish floors and vacuum periodically to minimize dust indoors.
Finally, three tips
First, for operable sashes (as opposed to ones that don’t move), there should be a 3/16 in. space between the sash and jamb on each side–3/8 in. total–so there’s room for weatherstripping as well as movement.
Second, refurbish jambs, too. Pull any old nails or screws sticking out, sand jambs smooth, prime all bare wood and then, when the paint’s dry, rub paraffin–a candle stub will do–along the jambs to allow windows to move easily. Do the same with the sides of refurbished sashes. If you must remove casing to get at sash weights, pulling finish nails through the casing causes less damage than pulling nails from the front.
Third, ace restoration carpenter Mike Davis in New Orleans recommends coating jamb channels with Dupont’s Corlar and Imlar products for a slick surface, though they are available only through industrial suppliers. A high-gloss marine enamel works almost as well. Davis also recommends www.conservationtechnology.com if you’re looking for a wide choice of airtight seals for old windows.
Thanks to Wooden Window, Inc. of Oakland, CA, for allowing me to photograph its crews on the job. This posting is excerpted from Renovation 4th Edition, just published by Taunton Press. R4’s 614 pages include thousands of field-tested tips and techniques, 250+ technical illustrations, roughly 1,000 photos selected from the 40,000 I have taken over the years, and lifetimes of experience that builders have shared with me. I hope you find Renovation 4th Edition useful on your next project. — Mike
© Michael Litchfield 2012
1. Refurbishing starts with detective work. Note what's working and what's not and figure out why. After removing the parting stops and the bottom sash of a double-hung, move the upper sash to see why it's sticking. Often, the sash will have swollen and become too wide for the frame.
2. The pros weigh sashes to ascertain how much weight is needed to offset them. Ideally, weights should weigh about the same as the sash they counterbalance so that the sash will stay at the height you set it.
3. Today's sash weights come in varying sizes, so you can combine them to approximate the weight of the sash. In the old days, oversized weights often lead to sashes that slammed into place--or jammed.
4. Sash cords should be long enough to knot at both ends--one knot around the sash weight, the other inserted into the side of the sash--yet short enough to keep the weight from touching the bottom of the cavity. Weights that hit bottom can jam.
5. Before reattaching sash cords, lubricate pulley wheels so they won't squeal.
Renovation 4th Edition contains the collective wisdom of hundreds of master builders and tradespeople across North America.