0instructodad_ 2 years ago Hi Valcollision,In general, these types of questions need more detail. It depends on the weight of the person, the size of the box, the type of foam, are you reinforcing with something else, etc... However, in this case, I would say it’s probably not a safe idea without a considerable design effort. The corners would likely be weak and could compress/tear over time with use. In damp locations or in high humidity, the box would deteriorate quicker. The type of foam you buy will determine how much the middle of the step compresses (something like ‘Great Stuff’ probably would be too weak unless it was a very short step up) older folks tend to have more trouble with balance, so any unevenness as the step wears with use could be an issue.Also, expanding foam can be pretty expensive. There may be other cheaper options to build the step. You could build a box/step with pallet wood and some basic hand tools for the same cost. It depends on your end goal I suppose! (I like the option that leaves me with more tools!)Sorry, long answer :) in short you could probably stand on it, but it wouldn’t be safe for grandma’s repeated use unless very well designed.