panels 5 may be enhanced by the location within hollow aperture 16 of a thin rectangular section steel or plastics tube 18 which not only assists in maintaining edge to edge alignment of wall panels from top to bottom but also provides additional reinforcement against lateral wind loads typically the abutting ends of wall panels 5 will be coated with a gap filling flexible polymeric adhesive to maximise the insulating properties of the wall structure and otherwise to accommodate any minor movement due to thermal expansion and contraction of the panels where the rectangular tube 18 is located in the hollow aperture 16 between adjoining panels it too may be secured with adhesive but it need not extend completely between the upper and lower channels 12 20 as it is not needed as a structural load bearing member rather a key to maintain channels 16 a in alignment it readily will be apparent to a skilled addressee that the panel edge joints whether reinforced with tube 18 or not are thermally efficient as there is no conductivity path from one side of a wall structure to the other a first embodiment of a roof for the building structure is illustrated in fig5 in this embodiment the roof 4 has a minimum pitch typically of from 3 to 10 degrees and is supported directly by the external load bearing walls 30 and by the internal load bearing walls 31 the roof may also be comprised of modular panels as discussed in more detail below in relation to fig6 a the roof panels 33 are secured at one end to the external walls 30 by screws 34 which pass through the roof panels 33 compression member 21 and.