The Name Of This Movie?

I've been trying to remember the name of this movie for a long while. I used to watch it when I was younger. Here's the stuff I remember about it (which, admittedly, isn't much.)

-Had to have been released somewhere in the very late 70's to mid-80's. I was still a kid when I saw it. It was shown on a movie channel, if I remember right.

-The characters were possibly restoring an old building which might've been a church or monastary. It's really hard to remember what it was at this point.

-I remember they were trapped inside the place and tried a bunch of ways to get out.

-One scene had a guy looking like he was trying to use an electric saw to cut through the large main doors, but was really cutting through his arm and possibly laughing about it.

-The ending had a guy manage to escape, running away from the building happy as hell only to fall into some kind of quicksand stuff and sink to his death.

I know thats not much to go on, but maybe it'll jog a memory or two from somewhere here.

Thanks,
BOTB