About the most common question asked related to transoms installation is "Will I need to remove my current transom?" The answer is no! For a current window, under about 30 year old, or for one you are currently planning to install the standard commercial units are double pane insulated glass. The stained glass panels I construct are installed as inserts over the interior side. The existing double pane window is not altered or even touched.
The only time I have constructed transom panels that are directly exposed to the outside is for replacements for older homes, usually pre-1900, that want or need to keep their original look for historical restoration reasons.
If you are having a new transom window installed and think you may want a custom stained glass panel make sure you order a transom that is just clear glass with NO interior lattice work. I have constructed stained glass panels for windows with such lattice work but it limits the design options since I need to position came to line up with the lattice lines.
Most transom windows will have some amount of window trim space as well as some amount of
sill space. The photo on the right shows what I mean by "sill" and "trim" areas via the
marked arrows. Some transom areas will have no trim area, that is to say the exposed glass
will extend out to the sill. This arrangement can be easily handled although about 1/2"
of the exposed glass will be covered by the outside metal trim of the stained glass panel.
The recommended sill depth is about one inch. If your area has less sill depth please let me
The photo also shows that for this case there is a small inner recess of the actual glass surface and the trim area. I would usually recommend mounting the stained glass panel on the outer sill leaning against the white trim area marked in the photo.
The second photo on the right shown common oak quarter round molding surrounding the inside perimeter of the stained glass panel to hold it in place. Only this molding is attached to the existing window sill. The stained glass panel sits on the sill. I supply small polyurethane bumpers that are placed on either side of the outer frame of the stained glass panel. These keep the panel from direct contact with the existing trim and the molding. So the panel will not rattle yet is held in place with a soft but firm fit. I supply a detailed installation document for use by you or your contractor.
To see sample guidelines for interior transom installation use the following link -- Transom Installation Guidelines. It assumes you have the Adobe Reader available.