Bay & Bow Window Replacement in Sunnyvale, CA
A bay is a small structure, not a big window. What holds it up matters as much as the glass.
The Cables Matter More Than the Glass
Multi-unit projecting window assemblies including support, head board, seat board, and roof detail.
A bay carries its own weight plus whatever roof sits above it, and none of that load is under the assembly. It gets transferred back into the wall by support cables or knee braces. A bow is the same idea spread across more, shallower angles.
So the glass is the easy part. What decides whether a bay lasts twenty years or sags in five is the support system, the seat and head board construction, and how the bay roof is flashed where it meets the wall.
Signs a Bay Needs More Than New Glass
A visible sag or a gap at the top
The assembly is dropping away from the wall. That is the support system, and it has to be corrected before any glass goes in.
Water staining on the seat board
Marks in the corners or along the seat mean the bay roof or its flashing is letting water in.
Rot in the head or seat board
Soft wood in either board means structure to rebuild, not just units to swap.
A leaking bay roof
Failed flashing where the bay cap meets the wall is the most common leak point on the whole assembly.
Fogged units in two or more panels
Multiple failed seals across the bay, usually the same age and failing together.
You want a different panel count
Going from three panels to five, or bay to bow, is a full reconfiguration of the opening and the support.
How We Do It
- Step one
Inspect the structure first
Support system, seat board, head board, and roof, all checked before we price a single unit.
- Step two
Rebuild and correct the support
Rotted structure replaced and a proper cable or brace system installed where one is missing.
- Step three
Set the units and align the mulls
Panels set to the correct angles with the mull joints lined up, because a bay shows every millimetre.
- Step four
Reflash, insulate, trim
Bay cap reflashed and re-roofed, seat and head insulated, interior trimmed out to match.
The 1980s Bolt-On Bay Problem
Bays added to Sunnyvale ranch homes during 1980s and 1990s remodels were often bolted on without a proper cable-and-brace system. The original window was fine; the addition was never carrying its load correctly. When we find one, that is the real repair, and it goes into the written quote before the glass does.
Structure before glass
Support, seat, and head board assessed and corrected as part of the job.
Bay roof reflashed
The wall junction is the leak point, so it gets done properly rather than patched.
Written scope
Carpentry and glazing itemised separately so you can see what you are paying for.
Bay and Bow Questions
Because you are buying carpentry as well as glass. Multiple mulled units, a support system, a seat and head board, a small roof, and flashing at the wall junction. The glass is a minority of the work.
If it is sound and dry, often yes, and that saves money. If there is any softness or water staining it comes out, because covering it up just delays the same conversation.
Usually the flashing does, because that is where bays leak. Whether the whole cap is re-roofed depends on its condition, and we tell you which after the inspection.
Yes, but it is a reconfiguration rather than a swap. Different panel count, different angles, and a support system sized for the new geometry. It is a bigger job and we quote it as one.
Related Services
Let Us Look at What Is Holding It Up
We inspect the support, the boards, and the roof before quoting anything, then price the carpentry and the glass separately so you can see the real scope.
Contact DetailsFree in-home measure
(408) 547-4680 — book the inspectionMonday to Friday 7:30am to 5:30pm · Saturday 8:00am to 2:00pm