[altacc]

It may not have been the customisation, more the processes of pre-fab in general and what the production process is. I didn't build my house but it's a recent pre-fab build, straight from the catalogue (a Swedish company). The amount of shoddy workmanship and shortcuts taken is surprising and I'm slowly correcting replacing a lot of the door & window surrounds, some floor supports, broken wiring, badly aligned panels, etc...

The overwhelming downside of not needing professional builders to build a house is not having professional builders build a house. Half-assed amateurs aren't going to give you the quality you expect for your home.