radially disposed these sections do not meet in the center leaving a vacant area this vacant center is covered by a skylight b or roof cap at the top and by removeable floor section at the bottom each of the individual sections a shown in perspective fig2 are preferably of light weight rigid foamed plastic having a 34 c 34 shape in cross section consisting of a floor exterior wall with opening for a sliding glass door and a ceiling roof each section is molded with a tough outside skin and a highly insulative structural foam core male and female slidably engaged mechanical alignment means d are fashioned on opposite and mating locations so that each individual section a is positively matched to the adjacent section and when the sections are drawn together the structure becomes integral sections a have threaded bosses c fig2 which receive bolts f fig4 which are tensioned thru upper and lower tension rings e fig4 thusly as the bolts are tightened the sections squeeze together in compression due to the nature of this shape this compression causes the roof section to gain a lifting force and imparts a high degree of rigidity into the structure seven sections provide an excellent combination for a well balanced interior floor plan fig3 consisting of two sections for the living area three sections for bedrooms and one each for bathroom and kitchen thusly each has light is of good size for portability and livability the vacant center area makes a most efficient hall opening into the radially located rooms when covered with a removeable floor the vacant center section is ideal for locating means for holding the structure down for sewer water gas or electrical hookups the.