Most homeowners don’t know that their windows aren’t working properly until they fall out or there’s too much of a draft for the homeowner to handle. Wood rot is usually referred to as “the silent killer” of curb appeal and energy efficiency because it will usually be hidden from view thanks to regular intervals of painting. Your window may appear brand new when in fact, the wood underneath is being turned to mulch every time it rains or snows.
If you’re asking yourself how to know if a window frame is rotting, the best DIY method to use to diagnose your window frame is called the “Screwdriver Test”.
Why is my window frame soft?
A “soft spot” typically occurs by moisture being trapped between the wood fibers and the top coat of paint. While the top coat remains good and looks good the moisture settles into the wood and damages both the surface of the wood and its structural integrity from the inside out. Soft spots are generally located near the bottom corners or any window seam.
Is wood rotting a threat to your windows? Absolutely. If you don’t take immediate action on wood rotting, you may be faced with:
- Higher energy bills due to air leaks.
- Mold growth and moisture damage inside your walls.
- Structural damage, as rot can spread to the internal studs of your home.
- Expensive full replacements rather than simple repairs.
How to test wood rot around windows
To understand how to check window frames for rot, follow these professional steps used by our technicians:
- Identify the Target: Look for areas that appear to have slightly “wavy” or bubbled paint.
- Apply the Tool: Use a small screwdriver, awl, or pocketknife and press into the wood, concentrating on the joint, where the two boards meet.
- Evaluate the Resistance: If the tool goes right into the wood like pressing into butter, the wood is beginning to rot from within.
- Confirm Solid Wood: Healthy wood is firm and solid when touched without small finger pressure; when pressure is applied to the wood, the tool should not penetrate the surface.

This is the most reliable way to determine how to check window frames for rot before the damage becomes visible to the naked eye.
Soft spots in window frame: What to do?
If your test reveals rot, do not simply paint over it. Painting over rotted wood traps the decay and allows it to grow faster underneath the new layer.
At RottenWindowRepair, we offer “surgical” methods for restoring your window frame. When we restore the window frame, we remove only the areas of decay and replace with better quality wood than that originally used. There are three components:
- Rotten Wood Replacement: We replace damaged sections with high-quality wood, preserving the strength of the frame.
- Sash and Sill Repair: We restore the movable parts of your window to ensure smooth operation and prevent water intrusion.
- Preservation: The methods we use to restore the window frames allow us to preserve the existing windows at a significantly lower cost than the cost of new window frames.

Why Choose Rotten Window Repair?
We have been in the Chicagoland area for over a decade and pride ourselves on honesty and craftsmanship. We provide a 10-year warranty on woodwork and a 20-year warranty on new glass units.
Prevent wooden window rot from spreading by contacting us for a free, no obligation in-home assessment. The estimate from us will include everything required to correct the condition at one fixed price so that you will not need to consider the cost of having to spend hidden fees.
- Phone: +1 (630) 716-6181
- Website: rottenwindowrepair.com