Restoring Double Hung Window Sashes

Windows | Last modified on: 28 Nov 2007 @ 20:54:09

Are you ready for a revolutionary new weight-loss system? I call it the old house weight loss plan. It involves painting the exterior trim in 90+ degree weather and in a couple of hours you'll sweat what seems like 10 pounds of water. That's what I did this morning.

But if you're not too keen about my weight loss plan, maybe it's a good time of the year to tackle an inside project. Keith Johnson, a Dundee neighbor, has just such a project-restoring the inside surface of his window sashes and he had a few questions:

A while back in your article in the Dundee-Memorial Park Association news, you promoted the retention of the older double hung windows rather than replacing them with vinyl. Last year we replaced all our storm windows but kept our double hung windows (6 panes on top, one pane on the bottom) in part because of what you said about them. We had all the panes re-puttied because many were loose.

Anyway, our sashes have not been very well maintained. The wood has been damaged by the raging sun of Omaha, especially the top surface of the lower sash. The finish is basically gone plus there may be years worth of dirt, smoke residue and who knows what accumulated on these surfaces. The wood appears to be quite dry and is a little cracked in some places.

How can we bring these sashes back to life? Should we wash the wood - if so with what? Should we sand the wood? Since the wood appears to be dried out, should we treat the wood with some oil (linseed?) before we try to stain and finish the wood?

There is always the problem that as we work on the upper horizontal piece of the lower sash, it is in intimate contact with the lower horizontal piece of the upper sash and liquids run in between the sashes. A number of sashes have been painted in our house and when you raise the lower sash, every color of paint is painfully apparent on the wood that is exposed on the upper sash. Is there any way to avoid this problem other than raise the lower sash when one is working on it?

First, congratulations, Keith, on saving your old windows. I firmly believe that unless your window's sashes are broken or rotted beyond all hope, then they are worth restoring. Now let's address some issues on restoring the interior surfaces of a window.

Let's talk about the last question first-paint and stain dripping onto the lower horizontal rail of the upper sash. The easiest way to avoid this is raise the lower sash or lower the upper sash (if it isn't painted shut) so they are not in contact. Another and better solution is to remove the lower sash, refinish it and then reinstall it. While it's a pain in the..uh..neck to remove and reinstall the lower sash, you'll be happier with the finished result. This is also a way to refinish the lower horizontal rail of the upper sash that is probably an ugly collage of paint and stain colors from years of painting and repainting.

Yes, I would wash all the old grime, smoke and residue off the windows. I would recommend using a solution of water and liquid dishwashing soap. A stronger cleaning agent like TSP (Trisodium phosphate) will clean better but can stain the wood, so I would only use that if you are going to paint the surface. If there is any varnish left on the sashes, you'll need to strip it off. Typically the varnish is so old and worn down that it will just melt away under a single application of chemical stripper.

A quick hand or power sanding with a fine grade of sandpaper (220 grit) is worth the effort so the sash will absorb the stain evenly and the finished surface will feel smooth to the touch.

I would not apply linseed oil on the sashes unless I was going to paint because linseed oil may darken the wood in an unpleasing way. Penetrating wood stains like MinWax have oils in their formulations and will help rejuvenate dried out wood. Another finish option is Danish Oil. (Watco is one brand I have had good luck with.) This might be a better choice than stain and varnish if the sashes are exposed to a lot of harsh direct sunlight. No finish will stand up to direct sunlight. Over time they will all fail. The advantage Danish Oil has is that it penetrates into the wood. After a few years when the surface needs some refreshing, you just lightly steel wool the surface and apply some new Danish Oil with a rag. If you are looking for a high gloss finish, then don't choose Danish Oil. It will dry to a nice luster but will not achieve a glossy look no matter how many coats you apply.

If exposure to the sun has created really deep cracks, the wood stain and varnish or Danish Oil may not be enough to make them disappear. You have a couple of options here. One option is to fill the cracks with color matched putty. (Do this after you stain the frame but before you apply varnish so you can get a good color match. Many wood fillers advertise that they will take stain. Yes, they take stain but I have never seen one that takes the stain the same way as the surrounding wood. So stain and then fill.) Your other option is to live with a few cracks and look at them like wrinkles on a well-aged face-a sign of character.