Old Wood Windows: Glazing and Paint

Original wood windows are one of the things that make an older home in San Diego look like itself: the narrow muntins of a Craftsman in North Park, the deep sills of a Spanish Revival house in La Mesa, the double-hung sashes on an old wood-sided home in National City. They are also some of the most demanding pieces of a house to paint well, because every sash is a small assembly of wood, glass and putty, and each part fails in its own way.

Painting them is less about the paint than about what is done before it.

What goes wrong with old wood windows?

Most of the trouble starts in the same few places. The putty that holds the glass dries and cracks; the paint along the bottom rail and sill wears through; years of coats glue the sashes shut. Each of these lets water reach wood, and wood is what has to be protected.

The parts worth knowing by name:

• The sash, the frame that holds the glass, with its rails top and bottom and stiles on each side.
• Muntins, the thin bars that divide the glass into panes.
• Glazing putty, the bevelled bead around each pane on the outside.
• Glazier’s points, small metal tabs pressed into the wood that hold the glass in place under the putty.
• Stops and parting beads, the strips that guide the sash as it slides.

On west- and south-facing windows, sun is the main enemy of the putty. It dries it out until it cracks and falls away in chunks. Near the water, damp mornings keep the bottom rails wet.

Why does failing putty matter so much?

Glazing putty is the seal between the glass and the wood. When it cracks, water runs along the glass into the corners of the sash, where the joints are, and sits there. The joints soften, the paint lifts and the glass loosens. Paint brushed over cracked putty will fill the cracks for a while, but the putty underneath is still shrinking, and the cracks return.

Where the putty is sound, it stays. Where it is loose, cracked through or missing, it is replaced.

How is a window reglazed?

The work is done carefully, one pane at a time.

1. Remove loose putty. Failed putty is cut and scraped out without cracking the glass. Sound putty that is still firmly attached is left in place.
2. Check the points. Missing or rusted glazier’s points are replaced so the glass is held firmly.
3. Clean and prime the bare wood. The rabbet, the ledge the glass and putty sit on, is primed. Putty laid on bare wood loses its oils into the wood, dries out and cracks early.
4. Lay new putty. The putty is pressed in and tooled to a clean bevel, so water runs off the glass rather than sitting on the joint.
5. Let it skin. Traditional glazing compounds need time to form a skin before they are painted. The product label gives that time, and it varies with the product and the weather.
6. Paint it. The putty is painted along with the sash.

Preparing the rest of the sash

While the putty is curing, the wood around it is prepared.

• Loose and failing paint is scraped off, and the edges feathered so they do not show as ridges.
• Soft wood at the bottom rail or corners is repaired. Small areas can be rebuilt in place; see epoxy filler and consolidants for exterior wood.
• Sashes painted shut are cut free along the joints, carefully, so they slide again.
• Hardware such as sash locks and lifts is removed or masked.
• Bare wood is primed.

A word about older paint

Many homes in San Diego, La Mesa and National City were built before 1978, and the old paint on their windows may contain lead. Windows matter more than most surfaces here, because a sash rubbing against its frame wears old paint into dust over the years. That changes how the old surface may be scraped and sanded. Ebenezer is EPA lead-safe (RRP) certified, so on a home of that age your windows are prepared with lead-safe practices: containment, wet scraping and sanding, and a careful clean-up. Ask about it at the estimate and you will get a straight answer about how your windows would be prepared.

Painting the window

The order on a window runs from the inside of the frame outward, so that wet paint is not brushed over by a hand or a sleeve. Muntins first, then the sash rails and stiles, then the frame and casing, then the sill. A brush is the tool here: windows are detailed work, and a sprayer would put more paint on the glass than on the wood.

Carry the paint onto the glass. The paint is brought over the putty and onto the glass by a very small margin. That thin line seals the joint between putty and glass so water cannot get behind it. A line that stops short leaves the joint open.

Keep the sliding surfaces thin. The parts of the sash and frame that slide against each other get as little paint as possible. Heavy paint there is how windows end up painted shut again.

Keep the sash moving. While the paint dries, double-hung sashes are moved up and down at intervals so they do not stick to their stops.

Choose a durable sheen. Trim and windows are usually painted in a satin or semi-gloss enamel, which sheds water and cleans well.

What it takes

Window work is slow, careful hand work, and on a house with many original windows it can be a large part of the job. It is also where the result shows most: windows are what you look at, and through, every day. Ebenezer has said, “Paint to me is an art.” Old windows are a good place to see what he means.

Windows are part of the trim on every exterior painting project he takes on, and they follow his usual order: wash, repair, mask, paint. If your home has original wood windows that need care, ask for a free estimate. Ebenezer will look at each one and tell you what it needs to be sealed, working and painted properly again.