I've seen a lot of old records with occupations like "builder and house jobber" or "slater and house jobber".
Until your post, I had just assumed it was basically saying that in addition to his primary trade, the man could turn his hand to anything in the house in the way of what we would now describe as "handyman" and could be "paid by the job" (like piece work). Maybe that assumption is wrong, I'd love to know the correct meaning.
BTW, be aware also that "house jobber" in the context of Dublin in latter 1800s / early 1900s had a very particular meaning, which doesn't seem to fit your man. With demand exceeding supply, Dublin "house jobbers" bought up lots of old houses with the intention of doing the minimum to preserve them and maximising rental income. Hence overcrowding, poor living conditions etc.
As I said, it doesn't seem to fit...