Bay or bow?
| Bay | Bow | |
|---|---|---|
| Units | Usually three: a large center unit and two angled flankers | A run of four to six matching units that curves |
| Typical angles | 30 or 45 degrees off the wall | A shallow arc |
| Projection | Deeper; a real seat or shelf | Shallower; more glass, less floor |
| Common flankers | Double-hung or casement | Casement or fixed |
Both hang outside the wall plane, so both need support underneath (cables to the header, knee braces or a framed foundation) and a small roof or head-board above.
Replacing an existing bay
Many 1970s and 1980s brick homes in west Knox County and Blount County have bays with wood flankers that have rotted at the sills, or a seat board with no insulation under it. Replacing the whole assembly lets the installer:
- Insulate the seat and the head, which are often bare plywood with nothing behind them.
- Swap the flankers to casements for better airflow and a tighter seal.
- Re-flash and re-roof the small bay roof, which is a common leak point in heavy rain.
- Check the support cables and the sill framing for rot before new glass goes in.
Adding a bay where there was a flat window
Turning a flat opening into a bay usually means widening or re-framing the opening, which is structural work. In the City of Knoxville, the 2018 IRC applies and residential construction work requires a permit unless exempt; changing an opening's size is not a cosmetic swap. Plan on a permit, and in Knox County a job of $3,000 to $24,999 calls for a contractor with a Tennessee Home Improvement license.
If the house is in a historic overlay such as Old North Knoxville or Fourth and Gill, a new projecting bay on a street-facing wall is the kind of change the Historic Zoning Commission reviews closely.
Glass and comfort
A bay puts three or more panes at different angles to the sun, so at least one usually catches afternoon light. Low-SHGC glass on the angled units keeps a south- or west-facing bay from overheating in a Knoxville summer. In winter, an uninsulated seat is the cold spot people notice; ask how the seat and head will be insulated. The label numbers are explained on energy-efficient windows.
Cost
Fixr's national installed ranges are $900 to $4,500 for a bay window and $1,500 to $8,000 for a bow, with labor alone reaching about $800 on these large units. Adding a new opening, a framed foundation or a copper roof sits outside those ranges. Compare against the Knoxville cost guide.
Back to the main guide: window replacement in Knoxville.