There are probably a bunch of stories with that premise but I'm reminded of Greg Bear's Blood Music (https://en.m.wikipedia.org/wiki/Blood_Music_(novel)). I read the novel but it's based on a short story he'd published previously.
They aren't Nanobots. The protagonist unofficially augments his own lymphocytes to create thinking 'noocytes' on company time and (mild spoiler) injects them into himself when his employer forces him to destroy this unauthorised experiment.
[Edit]
It's great sci-fi with elements of horror, especially when people who are immune to the noocytes discover what they are doing to the world. The "'integrating' him into the fabric of his house" you mention actually happens to different characters (at least in the novel), which is what is so horrific to immune people.
[Edit 2] Another book by Bear that suddenly swerves from sci-fi to horror is 'Psychlone', which has one of the most disturbing 'stuck in cabin in haunted woods' passages I've ever read. I actually got rid of my paperback copy because I really never wanted to experience it again. It now seems out of print, and is listed in Bear's wikipedia bibliography but doesn't have its own page.
The work was originally a short story, but was later rewritten as a novel.