ᐅ Add a secondary weather seal to wooden windows (existing building)
Created on: 25 Nov 2025 20:57
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GreatScott83G
GreatScott8325 Nov 2025 20:57Hello everyone,
I have an older house built in 1977/78 that we have been living in for about a year after nearly a year of renovation. This winter, an issue came up again that I had somewhat pushed aside: we wanted to replace the window seals, as some are torn, crumbling, etc. Currently, there is only one sealing layer installed in the frame, but I was told that a second sealing layer could be added to my windows (though no further details were given).
All my window sashes have a continuous, \_/ shaped groove (5mm (0.2 inches) wide at the top, tapering to 3mm (0.1 inches), and 5mm (0.2 inches) deep), and I was wondering what kind of seal would fit in there. I have looked through common sealing supply shops but haven’t found anything that seems suitable. Some instructional videos only show standard sash groove seals that don’t appear to fit this application. The most likely option I can think of is a simple tubular gasket, but I’m unsure how well it would stay in place. I also don’t think it should stick out too much.
I had planned to contact a window specialist who focuses on the restoration and maintenance of wooden windows, but they are currently fully booked and won’t be available for several weeks.
Thank you very much
I have an older house built in 1977/78 that we have been living in for about a year after nearly a year of renovation. This winter, an issue came up again that I had somewhat pushed aside: we wanted to replace the window seals, as some are torn, crumbling, etc. Currently, there is only one sealing layer installed in the frame, but I was told that a second sealing layer could be added to my windows (though no further details were given).
All my window sashes have a continuous, \_/ shaped groove (5mm (0.2 inches) wide at the top, tapering to 3mm (0.1 inches), and 5mm (0.2 inches) deep), and I was wondering what kind of seal would fit in there. I have looked through common sealing supply shops but haven’t found anything that seems suitable. Some instructional videos only show standard sash groove seals that don’t appear to fit this application. The most likely option I can think of is a simple tubular gasket, but I’m unsure how well it would stay in place. I also don’t think it should stick out too much.
I had planned to contact a window specialist who focuses on the restoration and maintenance of wooden windows, but they are currently fully booked and won’t be available for several weeks.
Thank you very much
N
NeuerAlter17 Dec 2025 18:01Hi,
77/78 marked a transition phase when people already wanted “more sealing” but didn’t yet know how rigorous to be. The groove in your photo looks very much like an old system groove, not a makeshift solution, even if it appears that way today. This _/-geometry is usually designed for a wedge or hollow chamber gasket, which compresses slightly when closing— not for the modern sash rebate seals sold online, which simply don’t fit in there, no matter what the product pictures claim. A tubular seal might theoretically work, but it only holds if the base fits precisely; otherwise, it loosens again after a few heating seasons, especially with wood that is still active. How strong is the draft actually right now? Are we talking about noticeable drafts at 0°C (32°F), or is it more a matter of comfort loss?
What’s often overlooked: a second sealing level only makes sense if the first one is still reasonably airtight; otherwise, you’re just chasing the airflow. And yes, window manufacturers are busy—I’m not surprised; nowadays, they prefer full replacement packages over such detail work because it brings in more revenue per hour, even if no one likes to admit it. It might be worth specifically looking for sealing profiles with a 4.5mm (0.18 inch) base; there are still manufacturers, but not at the typical hardware stores.
77/78 marked a transition phase when people already wanted “more sealing” but didn’t yet know how rigorous to be. The groove in your photo looks very much like an old system groove, not a makeshift solution, even if it appears that way today. This _/-geometry is usually designed for a wedge or hollow chamber gasket, which compresses slightly when closing— not for the modern sash rebate seals sold online, which simply don’t fit in there, no matter what the product pictures claim. A tubular seal might theoretically work, but it only holds if the base fits precisely; otherwise, it loosens again after a few heating seasons, especially with wood that is still active. How strong is the draft actually right now? Are we talking about noticeable drafts at 0°C (32°F), or is it more a matter of comfort loss?
What’s often overlooked: a second sealing level only makes sense if the first one is still reasonably airtight; otherwise, you’re just chasing the airflow. And yes, window manufacturers are busy—I’m not surprised; nowadays, they prefer full replacement packages over such detail work because it brings in more revenue per hour, even if no one likes to admit it. It might be worth specifically looking for sealing profiles with a 4.5mm (0.18 inch) base; there are still manufacturers, but not at the typical hardware stores.