How To Restore Steel Windows

By Scott Sidler • March 10, 2014

Historic Steel Window
Image Credit: Scott Sidler

Historic steel windows are all across America. They became popular in big cities to combat the fires that were so common around the turn of the 20th century. Then, from the 1930s until the 1950s, they were a popular choice in residential housing due to the decreasing availability of quality lumber.

Many steel windows sit and deteriorate across the country. While much attention has been paid to restoring traditional wood windows by preservationists, historic steel windows have fallen through the cracks. Well, that is something I would like to remedy here at The Craftsman.

We have put together a comprehensive guide to walk you through the process of how to restore steel windows. I’ll discuss the highlights here in this post to give you a primer on the subject.

If you really want to get down and detailed about working with historic steel windows, you should purchase and download my picture filled e-booklet. It is 12 pages of everything you’ll need to know about restoring steel windows. It includes:

  • Materials list
  • Detailed photos and breakdowns of each step showing exactly what and how to do it
  • How to get old hardware working again
  • Time tested techniques we use everyday

Pick up your copy right here!

The Craftsman’s Guide to Restoring Steel Windows


How To Restore Steel Windows


Putty removalHistoric steel windows are best restored in place, though with some effort, they can be removed from their opening and restored in a shop. The process is pretty straight forward and mostly focuses on removing the old glazing and paint down to bare metal before applying fresh coatings.

Step 1 Putty Removal

Old glazing putty on steel windows is often much harder than on historic wood windows. There is also a possibility that it contains asbestos so you should have it tested before large scale removal.

The best way we have found to remove the old putty is using an inexpensive wood chisel and hammer, but be careful of the spring clips that hold the glass in place. Once all the old putty is out, you’re ready for paint removal.

Step 2 Paint Removal

Scraping paint down to bare metal is essential here if you want your new paint to last. Use a ProScraper to remove any old paint. Once the paint is gone, sand the surface smooth and wipe all the sanding dust down with a damp cloth when you’re finished. Then, clean the glass as best you can before proceeding.

Step 3 Pre-treatment & Priming

Treat any rusted areas with a rust treatment like Ospho (this step is fairly complex and is described in more detail in the e-booklet). Then prime all the metal surfaces with a quality metal primer.


Step 4 Glazing

Glazing steel windowsOnce the primer is dry, you can proceed to putty glazing. You’ll need a putty designed for use on metal sashes like Sarco Dual-Glaze or DAP 1012. Press the putty into the glazing rabbets and finish the putty with a smooth bevel and clean 90 degree corners.

Follow the manufacturer’s recommendations for painting the putty. Some putty can be be painted right away, while others require a couple weeks to skin over before painting.

Step 5 Finish Paint

Top coat with a quality exterior paint. The paint should be lapped onto the glass about 1/16″ in order to seal the putty. You need to cut in a straight line with your paint brush and let the paint dry naturally in order to create a good seal. I recommend using an oil-based paint whenever painting a metal surface.

Complete all these steps (other than putty glazing) on the inside as well and your historic steel windows should be ready for another 50 years with only minimal maintenance other than regular paint jobs.

For a more in depth explanation of the process you should definitely pick up my e-book¬†The Craftsman’s Guide: Restoring Steel Windows

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74 thoughts on “How To Restore Steel Windows”

  1. I have a set of interior steel doors, am I able to keep the metal frames bare without painting? If so what is the best putty to use ?

    Thanks, E

  2. Can I use a heatgun to help strip off the paint on the casement windows? Can they be painted with latex or acrylic instead of oil paint?

  3. I’m looking for a company that does repair and restoration work in the Chicago area for my 1930s Tudor home. The steel casement windows are beautiful and still functional, but badly need some TLC before they deteriorate. My husband and I could possibly putty and paint, but there is a lot of rust and build up, in addition to missing machinery and frame issues, that we want someone who specializes. Any recommendations for our area?

  4. Scott
    I gave in to my wife and in the process of replacing our old steel casement windows with new clad double hung units.
    I have removed all the screws,scraped out caulk at masonry and seem loose from the inside, but cannot get the frames out – I was hoping to not cut them in half and actually trying to leave all the glass in place with hopes of passing them on to someone’s restoration project.
    Am I missing something with removal? Do you know anyone in the Charlotte. NC area that would want them?

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