Abstract: A floating roof storage tank having an upstanding tank shell for containing liquid to be stored and having therein a floating roof floating on the surface of the stored liquid, a primary seal interconnecting the floating roof and the tank shell, and an annular secondary seal extending between the floating roof and the tank shell providing a gas tight seal and weather shield for the primary seal, sealant is used at the inner end of the secondary seal mounted to the floating tank to ensure the gas tight connection thereat, and a tapered and rounded flexible free or outer end of the secondary seal ensures that irregularities in the tank shell do not permit vapors to escape; support structures maintain the secondary seal in its desired configuration and a variety of structures are disclosed for maintaining adjacent arcuate sections of the secondary seal in fixed and sealed relation.