Are you sure it is a Bay window or is it s Bow window?

A Bay window is made by projecting the foundation or cantilevering the floor joists so that you can actually walk into it. A Bay window, in other words, goes from floor to ceiling.

A Bow window, on the other hand, is simply a projected outward picture window.

If you really have a Bay window and it is sagging, you have some major structural problems that need to be addressed.

Bay windows need to either sit supported by a normal foundation or by properly installed joist canitlevers.

If you really have a sagging Bay window,it means either the foundation is failing or that the cantilevered floor joists have not been installed properly and to correct either problem could cost thousands.

A sagging Bow window, however, might be corrected by placing the proper angular supports under the bottom of its projection and could cost only a few hundred to correct.

You would do best to hire a professional contractor who can assess the problem and make a proper correction, then deduct it from the cost of the house, have the owner’s agree to pay to ahve it fixed. or walk away from a bad deal.