Well, the fact that these people are actually building on Christ is what saves them, though in the case of the straw, even their salvation won't be as much to speak of.
So there is the idea that people will receive glory in heaven ("crowns," etc.) according to what they did in Christ's name.
This is different from wholly refusing to do Christ's work -- not feeding the hungry, not clothing the naked, etc. -- such implies a total lack of identification with Christ, a lack of building at all on His foundation. Such will not be saved in the least, as Matt. 25 points out.