A friend of mine spent a couple years in Americorps with Habitat for Humanity here in Seattle. I've done several days of volunteering with them, but not for a while. The management seemed to have reasonable quality standards when I worked on site, sometimes asking for work to be redone if it wasn't done quite right. I'm far from a construction professional though; totally likely some things were missed. When the foreman is working for less than minimum wage on Americorps, and the rest of the labor has no experience besides occasional DIY on their own homes, there's only so much you can reasonably expect for quality.