Yeah, I used to buy cheap pants and tear them up in a week doing carpentry. This company makes some pretty durable pants:
Duluth Trading
Their 5-pocket jeans with the gusseted crotch are totally grandpa-lookin', but they have yet to fail on me despite abuse.
I haven't used their "Firehose" fabric pants, but everybody that does that posts reviews on the site can't say enough about 'em.