I have sidelights on either side of my front door - the glass pane is
app. 7 ft in length. I'm about to replace the sidelight and I noticed
that the plastic (i think) frame that holds the glass in place has a
cut in it that divides the frame into two pieces. The cut does not
look like it was done in a factory or anything - it is a little rough,
so I am assuming that the installer cut the frame.

We get a lot of sunlight on that side of the house. Is the cut there
to allow for expansion of glass/frame? When I install the new frame
and glass, should I cut the new frame too? The house is 17 yrs old,
so is this no longer needed with the new materials that have been
developed since then?

That 'cut' is likely actually a crack brought on by exposure to the
elements (freeze and/or heat). The same thing happened on two door
units of mine which are both steel door units, both painted black, and
both which bear the brunt of the sun - one in the AM, the other in the
PM. Conceivably it could also be from moisture or droplets which get
behind that fascia trim and whcih freeze in the winter resulting in
cracking of that trim....

On Aug 21, 12:11 pm, wrote:
I have sidelights on either side of my front door - the glass pane is
app. 7 ft in length. I'm about to replace the sidelight and I noticed
that the plastic (i think) frame that holds the glass in place has a
cut in it that divides the frame into two pieces. The cut does not
look like it was done in a factory or anything - it is a little rough,
so I am assuming that the installer cut the frame.

We get a lot of sunlight on that side of the house. Is the cut there
to allow for expansion of glass/frame? When I install the new frame
and glass, should I cut the new frame too? The house is 17 yrs old,
so is this no longer needed with the new materials that have been
developed since then?

The cuts looks too symmetrical for it to be cracks. The cut appear at
the same distance on each side of frame and they are perfectly
horizontal.

Not likely. There are screws that you can unscrew from inside the
house that removes the frame.