Friend of mine has a subaru Impreza. Tried to move some sandbags in it. Didn't work out. There's enough interior room, but because he had oversize tires, the suspension got weighed down so much that there wasn't anymore clearance. That was probably...200-300lbs of sand we tried to move. How does the Prius fare for moving stuff?
The Prius has about 850 lbs payload. That's passenger and cargo. I personally think you could put more provided you drive really slow. But I don't have any proof to support that.
i've put 5 or 6 bags of stone in the back, not sure of the weight, fairly heavy. not sure how strong the floor panel is.
I've had eight 40 lb bags (320 lbs total) of salt in the back and driven over neighborhood speed humps. Had no issues and it never bottomed out. That said, I would say I was close to true capacity loaded like that.
Prius is of course very spacious, but stated load limit is relatively low, like 820-840lbs. Four larger adults and luggage can overload it.
As others have said the Prius is rated for something like 850 lbs total. With something like sand you would want to distribute the weight throughout the car - some in the back, some on the floor of the back seat, and if you have no passengers some on the floor of the front passenger seat. For something like this you might want to pop for the $20 truck rental. If you get supplies for a couple of projects the cost is negligible.
