the ends of two parallel short frame members to define generally rectangular footprint of the portable restroom 10 two cross members not shown beneath the floorboard 30 extend in parallel to the short frame members and connect to the two long frame members at intermediate locations thereof in this way the frame 32 forms a rigid structure to support the weight of the cabin 12 the tank 14 and a user the frame members can be structural channel members having a c configuration which for the four outer frame members is oriented to opening inwardly the channel configuration provides for strength with relatively low weight and thinner walls allowing the floorboard 30 tank 14 and panels of the cabin 12 to be affixed to securely to the frame 32 using suitable mechanical fasteners the channel configuration of the frame members also facilitates attachment of the runners 34 specifically each of the runners 34 has an elongated foot that spans the depth of the cabin 12 and except for one extends beyond the front and rear of the cabin 12 to increase stability and reduce tipping the one shorter runner does not extend in front of the cabin 12 since it is beneath the door way and it could otherwise interfere with foot traffic into.