The rear part of my house really gets blasted by the rain. The
negligible roof overhang makes things worse. As a result, the
rear door to my deck is getting damaged, and tends to swell
up making it hard to open. As well, the trim molding is taking a
beating (cracking in places). The window next to the door is also
getting damaged.

I hired a company to install an awning over my rear door and
window. It is a fixed (i.e. not retractable) canvas awning,
protrudes 4' out from the building. My specific instructions to
them were to install something to protect the rear door and
window from rain.

We hard our first rain, and the awning didn't work at all. There is
a small gap where the canvas awning meets the side of the house.
Water is pouring through the gap, down onto the door and window.

Am I being reasonable in expecting the canvas awning to have kept
the water out? Before talking to these guys, I'd like to understand
whether their work was deficient, or if there was a
miscommunication and I wound up asking for something not
feasible.

wrote in message

My specific instructions to
them were to install something to protect the rear door and
window from rain.

We hard our first rain, and the awning didn't work at all. There is
a small gap where the canvas awning meets the side of the house.
Water is pouring through the gap, down onto the door and window.

Am I being reasonable in expecting the canvas awning to have kept
the water out?

This is a picky, but important point. They are protecting the door from
rain. They are not protecting the door from water running down the side of
the house.

There should have been better communication as to exactly what you wanted as
a result and what the capability of the awning is. Perhaps it can be
corrected with a different mounting setup, a flashing board over the awning
tops, etc. I'd guess that it can be corrected, fairly easily, and everyone
will be happy. Talk to the installer, let him know your problem, see what
he can come up with.