Bay & Bow Window Repair. Part by Part, Not a Whole New Bay.
Foggy glass, rotted mullions and seat boards, worn side-window cranks — we repair each part of a bay or bow window, so the whole thing doesn't need replacing.
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What Goes Wrong With Bay and Bow Windows
A bay or bow window is several windows joined together — which means several places for glass, wood and hardware to fail. The good news: each part can be repaired on its own.
A bay window has a large center window and two angled side windows; a bow window curves out with four or more equal units. The units are joined by mullions, and they sit on a seat board with a head board above.
Water that gets past the exterior seals soaks into the mullions and the edges of the seat board — the two spots where bay windows most often rot. The side units are often casements, so their cranks and hinges wear like any casement. And with so much glass, failed seals (fogging) are common.
We repair bay and bow windows part by part: replacing foggy or broken glass units, rebuilding rotted mullions and seat-board edges with matched wood, fixing side-unit cranks and hinges, and resealing the joints.
A leak coming from the roof above the bay is a roofing repair — we'll tell you if that's what we find. Replacing a whole bay usually means new interior trim, drywall and exterior work; repairing it keeps all of that intact.
People look for this as bay window repair, bow window repair, a foggy bay window, rotted bay window wood, or a bay window seat that's rotting.
Not sure this is your problem? Use our window triage guide — pick the symptom and see the likely cause and cost. Related reading: Rotted window repair · Foggy window repair
Foggy glass in one of the units
A failed seal — the glass unit is replaced, not the bay.
Soft wood at a mullion or the seat
Rot where the units join or at the seat board edge.
Side window crank spins or sticks
Worn operator on a casement side unit.
Drafts or water at the joints
Failed seals between units or along the seat.
- Mullions — where the units join; water that gets past the exterior seals soaks in and rots them.
- Seat board — the shelf the units sit on; its outer edge rots when joints leak.
- Center glass unit — large insulated glass; failed seals make it fog.
- Side-unit cranks — side windows are often casements with their own operators and hinges.
- Joints between units — the seals that keep water and drafts out.
Each part can be repaired on its own — the bay stays in place.
Bay & Bow Window Repair, Part by Part
Check every unit
Glass, wood, hardware and seals on each window in the bay — you get a clear list.
Repair the glass
Foggy or broken units replaced with new sealed glass made to size.
Rebuild the wood
Rotted mullions and seat-board edges cut out and rebuilt with matched wood.
Hardware & sealing
Cranks and hinges fixed, joints resealed so water stays out.
Bay Window Repair Cost
Typical prices
Per window · typical local prices| Glass unit in a bay or bow window | $300 – $800 |
| Rotted mullion or seat-board section | $200 – $700 |
| Casement crank on a side unit | $150 – $450 |
Because each part is repaired separately, bay window repair is priced by the parts that need work: a glass unit typically runs $300–$800, rotted wood sections $200–$700, and a side-unit crank $150–$450. Replacing an entire bay or bow window is one of the most expensive window projects in a house.
What we see in McHenry County bay windows
Many 1990s–2000s homes in Lake in the Hills, Huntley and Algonquin have clad bay windows whose glass seals are now failing, and whose side casements need new cranks. On older bays in Crystal Lake and Woodstock, rot at the mullions and seat-board edges is the usual repair.
What You Can Check Yourself
Safe to do yourself
- Check each unit for fog between the panes — note which ones.
- Press gently at the mullions and seat-board edges for soft wood.
- Crank each side window fully open and closed and note any that slip or stick.
Call a pro
- Removing glass or units from a bay — they carry weight and are sealed together.
- Caulking over soft wood — it traps water and hides rot.
- Climbing onto the bay roof — leaks from above are a roofing job.
Warranty on Bay Window 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
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.
Bay & Bow Window Questions
Bay & Bow Window Repair in these towns and more
Based in Lake in the Hills, serving homes within about 40 miles.
Keep Your Bay Window.
Call, text, or send a photo. You'll know what's wrong and roughly what it costs — before anyone comes out.
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