Bringing century-old steel windows into the 21st century
We have had the pleasure of upgrading original steel windows to improve their performance while maintaining their aesthetic and historic value. Original steel casement windows are still fairly common on some Seattle homes built during the first decades of the 20th century. Although most still look great, they usually leak air badly, both as a result of the original simple-overlap design, as well as due to distortions resulting from inadequate attempts to retrofit them with weatherstripping.
In the home shown here, many windows were leaking so badly that pieces of newspaper had been stuffed in to the cracks to reduce the drafts. Although exterior storm windows had been fitted throughout the house, they did nothing to help this, and in fact may have contributed to the problem by overloading the closure mechanism on some windows.
The windows were typically configured like this, with casement or awning-style operation, secured by a single surface-mounted handle. This particular unit had two operable sashes on either side and fixed panels in the middle and on the top.
Big air leaks were present between the operable sash and the fixed portions of all of the windows. Here you can see the top of the sash fit fairly well, but a big gap had opened on the bottom. In many cases, attempts to fit oversized weatherstripping had caused the sash to distort, bowing outward at the edges as the the single handle effectively compressed only the weatherstripping in the center of the sash. In addition, the strain had caused many of the original handles to fail.
Our remedy was to replace the single surface-mounted closure handle with a pair of through-the-rail closure handles. Through-the-rail closure is more secure than surface mounting, and less prone to distortion. We used handles cast out of silicone bronze like the originals, although we eventually had them treated to match the patina of the original hardware.
This is the kit that we used, showing (L to R) calipers, pilot bit, 15/32 bit for the through-the-rail hole, new custom-cast silicon bronze through-the rail window latch, Vix bit for piloting the screw holes, 5/32 bit for the screw hole, 10-32 tap for the screw holes, and silicon bronze 10-32 screws.
The procedure was pretty much the same for all of the windows.
We set up like this to collect all of the metal chips and other debris:
We used calipers to mark the 19/32” setback of the through-the-rail hole…
…drilled a pilot and a final 15/32” through-the-rail hole…
…fit the new handle in the hole and used a Vix bit to center the screw holes…
…drilled and tapped for 10-32 holes in the fixed rail to secure the handles…
…and test fit the new handles.
These images (from the outside with the sash swung open) show the handle being tested in the open…
…and locked positions. Note the shape of the cam, which is essential to draw the operable sash tight to the fixed rail. The distance between the cam and the fixed rail is also important, as it provides the clearance necessary for the weatherstripping. Selecting a closure handle with the correct clearance for the existing sash and rail configuration is the single most important step to ensuring success. Both the shape and the clearance can be modified somewhat on site, but not without difficulty, and not by much.
After the latches were test fit and ascertained to be moving well, closed-cell weatherstripping was custom fit to each window. The weatherstripping, almost invisible, shows up as the dark gap between the fixed rail and the sash.
Blower-door testing with chemical smoke confirmed that the weatherstripping worked almost perfectly. No leakage whatsoever could be detected by hand, with no newspaper caulking required.
After weatherstripping, the existing handles or other temporary closures were installed, and the new hardware was removed and treated with a process of chemical patina to simulate the appearance of the finish on the century-old latches that had been replaced. Compare this with the shiny, rosy handle in the test-fit image above.
The finished handle in this image, which is from another window, is also interesting because it has been modified for reverse operation, where opening the handle swings it in to the area of the operable sash. This is necessary because of the location directly adjacent to a plaster window jamb.
In addition to installing new latches, new pulls were installed in the location of the old latches. Here the old handle has been removed…
…and the old handle keeper has been ground down where it was welded to the frame…
…until it could be removed fully and the frame prepped for restoration…
There was a cut-away part of the frame underneath the handle keeper that had to be restored before the handle could be installed and the repair completed.
The final version of the pull is shown here, with the frame rail repaired and painted and the final finished version of the pull installed. The pull was finished with a process of chemical patina like the latches, to simulate aging of the bronze of the original handles.
Note that the original brass strike (visible in the center of the pull) has been allowed to remain as a reminder of the original latches.
The final outcome looks as good as the original, with performance on par with modern high-performance windows. We’ll look forward to upgrading them again in another 100 years.