Window Frame & Jamb Repair
Window frame repair for rotted jambs and frame corners, rotted mullions between windows, and frames that warped or shifted — we rebuild and re-square the frame so the window works again, without replacing it.
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- All window types & brands
- Fully insured
- Price match
Signs You Need Window Frame Repair
Soft wood at the jamb bottoms
Rot where the side jambs meet the sill.
Gaps or cracks at the corners
Frame joints opening up and letting water in.
Rotted mullion between windows
The post joining two windows going soft.
Sticks or binds in one corner
A warped or out-of-square frame.
Drafts or daylight at the edges
The frame no longer seals against the sash.
Is Your Frame Out of Square?
Measure your window corner to corner, both ways:
- Corner to corner both ways
- Equal diagonals: square
- Binding corner: sash sticks
- Opposite corner: gap, drafts
- Over 1/4 in difference: it has shifted
- Measure corner to corner — with a tape measure, across both diagonals of the frame opening.
- Equal diagonals — the frame is square.
- Different diagonals — a difference of more than about 1/4 inch usually means the frame has shifted.
- Binding corner — where the sash rubs or sticks.
- Opposite corner — often the gap where drafts and water get in.
An out-of-square frame explains most sticking, drafty windows — and it can usually be corrected.
If the two diagonals differ by more than about 1/4 inch, the frame has shifted — and that's usually why the sash sticks or drafts.
- Check for gaps by closing the window on a strip of paper: if it slides out easily, the seal is not closing.
- Note which corner binds or leaks — it tells us which way the frame has moved.
Rotted, Warped or Shifted: What Happens to Window Frames
The frame is the backbone of your window. When it warps, cracks, or racks out of square, everything that depends on it fails too — the sash sticks, the seal gaps, and the lock stops lining up.
A window frame holds the sash in a precise, square opening. Over years, that squareness gets lost.
House settling shifts the rough opening and twists the frame; moisture makes wood swell, cup, and warp; a poor original installation that was never shimmed level eventually shows up as sticking and gaps down the line; and decades of paint buildup, hardware stress, and thermal movement all add up.
The frame ends up out of square — even when the glass and sash themselves are fine.
The good news: a frame problem is a matter of geometry and structure, and both can be restored. Rather than tearing out a whole window because it sticks or leaks, we bring the frame back to square, reinforce and repair the damaged areas, and re-establish the seal and lock alignment.
Frame repair vs. rotted wood
Frame repair addresses structure and geometry — warping, racking, cracks, and loose joints. That's different from rotted wood repair, which addresses decay — wood gone soft from moisture. The two often appear together, and we handle both; during assessment we identify which is driving your window's problem so the repair fixes the true cause.
Most frame repairs start with rot: the bottom of the side jambs, the lower frame corners, and the mullions between joined windows are where water collects. The rest are frames that warped, cracked or were pulled out of square as the house settled.
Either way the symptoms look alike — the window sticks, won't lock or lets in drafts — and the fix is to rebuild or re-square the frame, not replace the window.
Not sure this is your problem? Use our window triage guide — pick the symptom and see the likely cause and cost. Related reading: Rotted wood repairBasement window repairParts of a window
How We Repair a Window Frame
Diagnose the Cause
We check the frame for square, identify what moved it — settling, moisture, or install — and confirm whether rot is also involved.
Re-Square & Shim
The frame is brought back to level and plumb and properly shimmed, so the opening is square and the sash has room to move.
Repair & Reinforce
Cracked jambs, split corners, and weakened joints are repaired and reinforced so the frame holds its shape for the long term.
Reseal & Test
We re-establish the weatherseal and lock alignment, then test that the window opens, closes, seals, and locks smoothly.
Jobs that need a professional
- Planing or sanding a sticking sash — it hides the real problem and can ruin the fit.
- Forcing a window that binds — frames and glass crack under pressure.
- Removing interior trim to re-shim the frame — easy to damage plaster and trim.
- Large cracks through the frame or visibly bowed jambs — that needs structural repair.
Rotted Jambs, Frame Corners & Mullions
Frames rot from the bottom up. Water runs down the window, sits where the frame meets the sill, and soaks into the end grain.
Jamb bottoms — the lower ends of the side jambs — soften first, often behind paint that still looks fine. Frame corners open up where joints stop shedding water.
And where two or more windows are joined, the mullion between them collects water from both sides and rots from the inside out — especially in bay and bow windows. On clad windows, the wood frame can rot under the aluminum or vinyl cladding with little to see from outside.
We cut the rot back to solid wood, treat what's left, splice in matched wood shaped to the frame's profile, and seal it so water sheds again. The window stays in place. For rot in other parts, see sill repair, rotted sash repair, brick mold repair or bay window repair.
Window Frame Repair Cost
Minimum service visit: $150 — several small repairs in the same visit are covered by it.
Typical prices
Per window · typical local prices| Alignment & sticking windows | $50–$500 |
| Frame or jamb wood repair (typical) | $200–$700 |
| Sash repair if the frame damaged it | $400–$700 |
Repair vs. a new window, per window
A frame that's out of square is exactly the kind of problem a replacement company uses to justify a whole new window. But re-squaring, reinforcing, and repairing an existing frame costs a fraction of replacement — and keeps a window that, on most older homes, is built better than what would replace it.
Frames on older northern Illinois homes were frequently made from dense, old-growth wood that outlasts modern materials, and repairing the frame preserves both that quality and the home's original proportions and character.
Cost depends on how far the frame has moved and whether repair, reinforcement, or partial rebuilding is needed — we give you an estimate after a free assessment so you can weigh the real number before deciding. In the large majority of cases, frame repair is both the cheaper and the better choice.
Why frames shift in northern Illinois homes
Clay-heavy soils across the area expand when wet and shrink in dry summers, so houses settle slowly for decades — and window frames follow. Freeze-thaw cycles pry at every joint, and frames on the lake- and river-facing sides of homes in Crystal Lake, Algonquin and Fox River Grove take the most moisture.
Warranty on Frame Repairs
Parts we don't make (cranks, balances, locks) carry only their supplier's warranty. Leaks from roofs, flashing or siding aren't window defects. Full warranty terms Read our reviews
Who does the work
- Our own technicians — no subcontractors.
- About 10 years in the trade, on every kind of window and door.
- The same people who give the estimate come back to do the work.
Make the repair last
- Clean and lightly wax the sash tracks — dirt alone can make a window bind.
- Re-caulk small interior gaps where the trim meets the wall.
Got a quote to replace these windows?
Send it to us before you sign. We'll tell you — free — whether a repair would solve it for less.
What Customers Say
"Very responsive and extremely helpful. Fixed the rotting wood around our window the same day they came out to look at it. Greatly appreciate their assistance."
Window Frame Repair Questions
More Wood & Rot Repairs
Window Frame Repair Near You
Based in Lake in the Hills — we do window frame repair in Lake in the Hills and 35+ nearby towns, within about 30 miles. Find yours:
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Fix the Frame, Keep the Window.
Call, text, or send a photo. You'll know what's wrong and roughly what it costs — before anyone comes out.
★★★★★ 4.9 from 145+ reviews · 20-year glass warranty · Price match