How to Assess the Condition of Historic Windows

Read the Signs Before You Restore

Before grabbing a crowbar or declaring your historic windows a lost cause, take a breath - and a closer look. Many homeowners mistakenly think old windows are “too far gone” when, in reality, most are just calling out for a bit of TLC.

In this week’s post, we’ll walk you through how to inspect your historic windows like a pro so you can make smart restoration decisions and avoid unnecessary replacements.

Step 1: Look at the Big Picture

Stand back and assess the window from both inside and outside.

Ask yourself:

• Does the window open and close?

• Are both sashes present and operable?

• Are there visible signs of wood rot, paint failure, or misalignment?

Sometimes, what looks like severe damage is really surface-level—like peeling paint or a broken sash cord.

Step 2: Inspect the Frame and Trim

✔️ Check for Soft Spots

• Use a flathead screwdriver to gently press into the sill, jambs, and trim.

• If the wood feels spongy, crumbles, or flakes off, there’s likely rot.

✔️ Look for Gaps or Separation

• Cracks between the sash and frame may indicate shrinkage or movement over time - but this is often fixable with weatherstripping or filler.

✔️ Examine for Insect Damage

• Small holes, tunneling, or sawdust-like residue can mean termites or carpenter ants have visited.

Step 3: Evaluate the Sash

🪟 Rails and Stiles

• Check for warping or twisting. If the sash is bowed, it may still be repairable with clamping and reinforcement.

🪟 Muntins and Mullions

• Inspect the decorative dividers between glass panes for cracks or separation.

• Loose muntins can be reglued; missing pieces can often be replicated.

🪟 Glazing Putty

• Old, cracked, or missing glazing leaves glass loose and lets in moisture.

• This is one of the easiest things to fix with some putty and patience.

Step 4: Examine the Glass

🔍 Wavy, Bubbly, or Seeded Glass

• Congratulations - you likely have original historic glass! Treat it like gold.

🔍 Cracks or Chips

• Many cracks are cosmetic and can be stabilized or replaced with salvaged or restoration glass.

🔍 Loose or Missing Panes

• May indicate failed glazing, not a structural issue.

Step 5: Test the Operation

🎯 Stuck Sashes

• Often caused by paint buildup, broken cords, or warped tracks - not a reason to replace!

🎯 Weight and Pulley System

• If the sash slams shut or won’t stay open, the cords or weights likely need replacing.

🎯 Check for Rattling or Drafts

• Usually solved with weatherstripping and basic sash adjustments.

Step 6: Take Notes & Photos

Create a window-by-window assessment log:

• Window location (e.g., Living Room North Wall)

• Sash condition

• Frame condition

• Glass notes

• Operational issues

This will help prioritize repairs and communicate clearly with restoration professionals if needed.

When to Call in a Pro

If you discover:

• Major rot in structural framing

• Extensive insect damage

• Broken or missing sashes

• Historic district requirements you’re unsure about

… it’s best to get a professional evaluation. But for everything else, you may be surprised how much is restorable.

Conclusion: Most Old Windows Are Survivors

Historic windows were built with care, quality materials, and the expectation they’d be maintained - not tossed. By learning how to properly assess their condition, you’ll be better equipped to preserve their beauty and function for another generation.

Trust your eyes, trust your tools - and when in doubt, trust a good restoration expert.