Metal windows, particularly historic steel casement windows, can often be repaired and restored rather than replaced. While it may require some effort, restoring steel windows is a viable option that can maintain the building’s character and architectural integrity. In this comprehensive guide, we’ll explore the process of repairing and restoring historic steel windows, whether they are best restored in place or removed for shop restoration.
Assessing the Condition of Steel Windows
The first step in repairing steel windows is to carefully evaluate their condition. This involves examining the windows for signs of corrosion, paint buildup, deterioration of metal sections, and the condition of glass, glazing compound, hardware, and surrounding masonry or concrete. A professional contractor or window repair specialist can assist with this assessment and help determine the best course of action.
If the evaluation reveals that the windows are in basically sound condition, rehabilitation is the recommended approach. Areas of light to medium rust and excess paint can be readily removed, and select areas of extreme rust can be addressed by torching out damaged sections and splicing in new metal pieces that are then ground smooth.
Removing Paint and Rust
Before starting any repair work, it’s essential to shield adjacent interior and exterior walls, sills, and window jambs with plastic to protect them from debris. The next step is to remove rust and excess paint from all moving parts and components, including hinges, using either chemicals (but not hydrochloric acids) or hand-held tools like mini grinders or rasping files. Heated removal methods should be avoided.
Any remaining rust, debris, and loose paint should be gently cleaned off with a wire brush. Well-bonded paint can remain, although the edges should be feathered by sanding. It’s crucial to prime any exposed bare metal immediately after cleaning to prevent rust from recurring.
Repairing Severely Rusted Sections
If the corrosion is heavy with the rust penetrating deep into the metal, it may be necessary to remove highly rusting metal frames for refurbishment in a workshop. However, if severe corrosion is only in select areas, it may be possible to torch out bad sections and weld in new pieces that are then ground smooth, with the window unit in place.
Once the glazing and any old putty have been removed from the metal frames, paint and rust should be cleared from the surface of the metal to enable its condition to be inspected. In severe cases, neither wire brushes nor grinders can effectively remove the rust. Suitable alternatives include acid pickling and the use of air-borne abrasives.
Restoring Steel Windows In-Place vs. In a Shop
While historic steel windows are best restored in place, some effort may be required to remove them from their opening and restore them in a shop. The process is pretty straightforward and mostly focuses on removing the old glazing and paint down to bare metal before applying fresh coatings.
For steel windows that are removed and repaired off-site, future corrosion resistance can be achieved most effectively by hot dip galvanizing. This process involves fully immersing the frames in a bath of molten lead and zinc at high temperatures, ensuring complete surface coverage. However, hot dip galvanizing can be harsh and may cause historic windows to become distorted, so advice should be sought from a Galvanizers Association member beforehand.
Improving Energy Efficiency
One of the main issues with classic steel casement windows is energy efficiency, as steel is not a good insulator of heat or cold. While glass is far worse, heat loss from windows is primarily due to air infiltration rather than the material of the sash or the type of glass.
To improve energy efficiency, caulking, weather stripping, and new thermal glass can be installed. Clear window films with a high visible light transmittance (VLT) may also be applied to reduce solar heat gain. Interior storm windows, thermal/insulated window treatments, exterior awnings (where appropriate), and new shade trees at window locations can further enhance energy efficiency.
Conclusion
In conclusion, metal windows, particularly historic steel casement windows, can often be repaired and restored rather than replaced. By carefully assessing the condition of the windows, removing paint and rust, repairing severely rusted sections, and considering the best approach for restoration (in-place or in a shop), building owners can maintain the character and architectural integrity of their historic structures while improving energy efficiency. With the right techniques and professional guidance, metal windows can be brought back to life and continue to serve their purpose for many more years to come.