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Call or text(224) 209-0862
★★★★★ 4.9· 145+ reviews· 20-yr glass warranty
Rotted sills, sashes & frames · 40+ nearby towns

Rotted Window Repair: Sills, Sashes & Frames. Cut It Out. Build It Back.

Soft, crumbling or stained window wood can almost always be saved. We remove the rot, splice in matched wood, reshape it to the original profile and paint it to blend — with a 3-year warranty on the wood we rebuild.

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  • All window types & brands
  • Fully insured
  • Price match
Can it be fixed?Usually — rot is cut out and rebuilt
Typical price$200 – $700per window · confirmed before work starts
How longUsually one visit
Peace of mind3-year wood repair warranty
The Problem

How Window Rot Starts — and Why It Spreads

Rot almost always begins in one spot where water lingers — usually the sill or the lower corners of the frame. Caught early, it's a small, affordable repair. Left alone, it spreads into the frame, the wall, and eventually your interior finishes.

Window wood rot is caused by moisture: rain, snow, ice, and condensation working into the wood through failed caulk, cracked paint, worn glazing, or blocked weep holes. Once moisture is trapped, fungi break the wood down from the inside, turning firm timber soft, spongy, and crumbly.

Older wood is especially vulnerable because it loses its natural decay resistance over the decades — which is why rot is one of the most common problems on the area's older homes.

The good news: wood rot is highly repairable when it's addressed before it takes over the whole window. The key is a proper repair that removes all the decayed wood and stops the moisture that caused it — not a cosmetic patch that traps the problem underneath.

Where rot shows up first

The sill takes the most weather and rots first, followed by the lower frame and jamb corners, the bottom rail of the sash, and exterior trim and brick mold. We repair rot in all of these, and because they're connected, we check the surrounding wood so the repair is complete rather than partial.

Homeowners describe it in different ways — a rotten window frame, a rotted sash, soft wood around the glass, or paint that keeps peeling in the same spot. It's all wood rot, and window rot repair works the same way: find the full extent of the decay, remove it, and rebuild.

Larger areas get new wood spliced in (carpenters call it a Dutchman repair); small, shallow areas can be hardened with a wood consolidant and filled with an epoxy made for exterior wood.

Not sure this is your problem? Use our window triage guide — pick the symptom and see the likely cause and cost. Related reading: Window problems by home age · Window sill repair

Soft or spongy wood

Wood that gives when pressed, or that a screwdriver sinks into easily, has active rot beneath the surface.

Peeling or bubbling paint

Paint that flakes, bubbles, or won't hold is often a sign of moisture and decay working underneath.

Dark stains & cracks

Discoloration, dark patches, and cracking or gaps at the corners point to water intrusion and rot.

Musty smell or crumbling

A damp, musty odor near the window, or wood that flakes away in pieces, means decay is well underway.

Rotted wood exposed along the bottom of a casement window frame
Recognize this? It's a common, repairable problem.
Where rot starts on a wood window
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  1. Sill — water and snow sit here longest, so paint fails first.
  2. Bottom rail of the sash — water runs down the glass and soaks into it.
  3. Lower ends of the frame and trim — end grain wicks up water where they meet the sill.
  4. Glazing joint — cracked putty lets water into the joint between glass and wood.

Rot usually stays in these zones — which is why it can be cut out and rebuilt.

The Fix

Rotted Window Repair That Lasts

Remove All Decay

We cut out every bit of rotted wood back to solid, sound timber. Leaving soft wood behind is exactly why quick patch jobs fail.

Treat & Consolidate

The surrounding sound wood is treated with a penetrating hardener that strengthens it and helps resist future decay.

Epoxy or Timber Splice

Smaller areas are rebuilt with structural epoxy; larger ones get new matched-species wood spliced in and shaped to the original profile.

Seal, Prime & Match

Everything is sealed against moisture, then primed and painted to match — leaving a repair that's invisible and built to last.

How a rot repair works
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  1. Find the rot — soft, dark wood — usually at a sill, a corner or the bottom of a sash.
  2. Cut back to sound wood — every bit of soft wood is removed, so the rot can't keep spreading under the repair.
  3. Splice in new wood — matched wood is fitted, shaped to the original profile, then primed and painted to blend.

The rest of the window — and its original wood — stays in place.

BeforeRotted sill and frame wood opened up before repair
AfterNew wood spliced into the window sill during the rot repair
Rot by Part

Rotted Window Repair, Part by Part

Rot doesn't mean a new window — it means the part that rotted gets rebuilt. Find the part that's soft:

Rotted Window Sills

Exterior sills and interior stools rebuilt or replaced.

See the fix → $200–$700

Rotted Window Sashes

Rotted rails and corners rebuilt, or a new sash made to fit.

See the fix → $200–$700

Rotted Frames & Jambs

Jamb bottoms, frame corners and mullions rebuilt.

See the fix → $200–$700

Bay & Bow Windows

Rotted mullions and seat boards repaired part by part.

See the fix → $200–$700

Brick Mold

Rotted brick molding around windows rebuilt or replaced.

See the fix → $200–$700

Door Jambs & Door Bottoms

Rot at the bottom of door frames and wood doors.

See the fix → $200–$700

Whole Old Windows

Every part of a wood window restored at once.

See the fix → $400–$700

Clad windows rot out of sight. Many windows from the 1980s onward are wood covered with an aluminum or vinyl skin.

When the seals at the corners fail, water gets under the cladding and the wood rots with little to see from outside — until the sash feels spongy or a corner separates. If your clad windows have loose, bulging or stained cladding at the bottom corners, it's worth a look.

Repair vs. Replace

Rotted Window Repair Cost vs. Replacement

Replacing the window$800 – $2,500+
Repairing itFrom $200

Typical prices

Per window · typical local prices
Localized rot — sill or frame corner$200 – $700
Sash rot repair & restoration$400 – $700
Alignment after the repair (if needed)$50 – $500
Why the final price can differ: these are typical ranges, not quotes. What moves the price: the size and type of glass (tempered, low-E, triple-pane, decorative), how far rot has spread once the wood is opened up, second-story or ladder access, parts availability on discontinued brands, and how many windows are done in the same visit — multi-window jobs cost less per window. Minimum service visit: $150. We confirm and agree the price with you before starting. Compare all repair prices →

Replacement companies treat rot as a reason to sell you a whole new window. But rot is almost always localized, and repairing the damaged section costs a small fraction of a full replacement — while keeping the rest of a perfectly good window in place.

There's a second reason repair wins on older homes: original wood windows are often better built than modern replacements, made from old-growth timber that's denser and more durable than what's used today.

Replacing them swaps craftsmanship and character for a stock unit. A proper rot repair preserves the original window and, once painted, is impossible to spot. We provide an estimate after a free assessment, so you can weigh the real repair cost before making any decision.

Why rot is so common in McHenry County

Snow sits on sills for weeks, spring thaw soaks the bottom rails, and humid summers near the lakes and the Fox River never let the wood fully dry. Add the pre-war and mid-century homes in Crystal Lake, Woodstock and Carpentersville — built with old-growth wood that is well worth saving — and rot repair becomes one of the most valuable fixes a homeowner here can make.

DIY or Pro?

Wood Rot: What You Can Do Yourself

Safe to do yourself

  • Probe suspect wood with a screwdriver — if it sinks in easily, the rot is active.
  • Keep gutters clear and sills free of snow and ice so water drains away.
  • Touch up cracked paint on sills and sashes before winter — paint is the wood's first line of defense.
  • Photograph the soft area and the whole window, then text us for a quote.

Call a pro

  • Filling rot with wood filler or caulk — it traps moisture and the rot keeps spreading underneath.
  • Cutting out rot that reaches the frame joints — the window can lose its structure.
  • Rot you find around the outside of the frame or on the wall — that may be a siding or flashing leak.
  • Painted wood in pre-1978 homes — old paint may contain lead and needs safe handling.
Warranty

3-Year Warranty on Rebuilt Wood

3 yearson wood we rebuild or replace — if it rots, we replace it
20 yearsmanufacturer warranty on insulated glass units
Redoif we install hardware incorrectly, we come back and fix it

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

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.

Free Second Opinion
FAQ

Rotted Window Repair Questions

In the large majority of cases it can be repaired without replacing the window. Wood rot almost always starts in one localized area — usually the sill or the bottom of the frame — where water sits. As long as it's caught before it spreads through the entire structure, we remove all the decayed wood back to sound timber, treat and consolidate the surrounding area, and splice in matched new wood. Once primed and painted the repair is both structurally solid and visually invisible. Full replacement only makes sense when rot has compromised the whole window at once, which is far less common than replacement companies suggest.
The lasting fix is a multi-step process, not just filling a hole. First we cut out every bit of decayed wood back to solid material — leaving soft wood behind is why quick patch jobs fail. For minor to moderate rot, the surrounding sound wood is treated with a penetrating hardener and rebuilt with structural two-part epoxy that bonds to the wood and resists moisture. For larger areas, we splice in new matched-species timber (a 'Dutchman' repair) shaped to the original profile. Finally, everything is sealed, primed, and painted to lock moisture out. Addressing the moisture source — failed caulk, bad flashing, blocked weep holes — is part of the job, because that's what caused the rot in the first place.
The clearest test is to press the wood with a screwdriver or your thumb: healthy wood is firm, while rotted wood feels soft, spongy, or crumbles. Other signs include dark stains or discoloration, flaking or bubbling paint, visible cracks or gaps at the corners, a damp or musty smell, and pieces of wood that flake away easily. Rot most often shows up first on the sill and the lower corners of the frame where water collects. If you catch these signs early, the repair is small and inexpensive; left alone, rot spreads into the frame, wall, and even the interior finishes.
Two reasons: age and moisture. Communities like Carpentersville and historic Crystal Lake have significant pre-war and mid-century housing stock with original wood windows, and older wood loses its natural resistance to decay over decades. On top of that, northern Illinois delivers heavy moisture load — snow, ice, spring rain, and lake- and river-influenced humidity near the Fox River and the Chain O'Lakes — combined with freeze-thaw cycles that open up caulk joints and let water in. That combination of aging wood and constant moisture is exactly what drives rot, which is why it's one of the most common repairs we perform across the county.
Almost always, and often dramatically so. A localized rot repair addresses only the damaged section — a corner of the sill, the bottom rail of a sash, a length of trim — while keeping the rest of a perfectly good window in place. Full replacement means paying for a whole new unit plus labor and interior/exterior finishing. Repair also preserves original wood windows, which on older homes are frequently better built than modern replacements. We give you an estimate after a free assessment so you can see the repair cost before deciding — and in the vast majority of cases, repair wins clearly.
Yes. Matching is a core part of the work. We splice in the same or a compatible wood species, shape it to the original profile and dimensions, and finish it so the repaired section blends seamlessly with the rest of the window. Once primed and painted to match your existing color, a well-executed rot repair is essentially invisible — which is exactly why it's the right choice for preserving the look of older and historic homes rather than swapping in a modern replacement that changes the window's character.
Yes. We are based in Lake in the Hills and repair rotted window sills, sashes and frames across 40+ towns within about 40 miles, including Crystal Lake, Woodstock, Cary, Algonquin and Carpentersville. Call or text (224) 209-0862, or send photos for a free quote.
Localized rot in a sill or frame corner typically runs $200–$700 per window, and sash rot repair or restoration $400–$700. The final price depends on how far the rot has spread once the wood is opened up. That compares with $800–$2,500+ to replace the window. Our minimum service visit is $150.
Wood we rebuild or replace is covered for 3 years — if it rots, we replace it. The warranty covers our wood, not rot caused later by leaks from the roof, gutters, flashing or siding around the window.
In most cases, yes. Rot usually stays in the lower parts of the frame, the sill and the bottom of the sash. We cut those areas out and rebuild them, and the rest of the window stays in place. We'll tell you honestly if the rot has spread through the frame's structure.
It depends on the depth. Shallow, localized rot can be consolidated and filled with an exterior-grade wood epoxy. Deeper or larger rot is best rebuilt with new wood spliced into sound wood. We choose based on what we find once the damaged area is opened up.
Most localized rot repairs are done in a single visit. Larger repairs take longer because consolidant, primer and paint need time to cure between steps. We'll tell you what to expect once the damaged area is opened up.
More Repairs

More Wood Window Repairs

Window Sill RepairThe sill rots first — rebuilt or replaced.Learn more →Window RestorationFull rebuild of worn wood windows.Learn more →Frame RepairWarped or out-of-square frames restored.Learn more →Wood Window RepairEverything we do for wood windows.Learn more →

Rotted Wood Repair in these towns and more

Lake in the HillsCrystal LakeAlgonquinCaryHuntleyCarpentersvilleWoodstockMcHenryMarengoJohnsburgIsland LakeLakewoodAll service areas →

Based in Lake in the Hills, serving homes within about 40 miles.

Rot Caught Early Is a Small Repair.

Call, text, or send a photo. You'll know what's wrong and roughly what it costs — before anyone comes out.

(224) 209-0862Free Quote

★★★★★ 4.9 from 145+ reviews · 20-year glass warranty · Price match