above with the outer edge 15a of the membrane close to the lower edge 11a of the third tier above the nailing strip 17 39 of another assembly is then brought against the lower edge 11a of the third tier with the membrane 15 39 of the assembly in the trailing position shown in fig3 it will be noted that when the nailing strip of the second assembly abuts the lower edge of the third tier it overlies the upper edge portion of the membrane 15 of the first assembly 18 nails n are driven through the nailing strip the part of the membrane secured to the underside of the nailing strip and the sheathing the membrane 15 39 is swung counterclockwise around the nailing strip 17 39 and laid flat on the composition shingles of the third and fourth tiers fig5 is a diagrammatic vertical cross section of a typical roof having a covering of composition shingles that has been re covered using the shingle assemblies 18 of the present invention in many roofs having composition shingles the lower edge of the lowermost tier of shingles terminates substantially flush with the lower edge of the sheathing and rafters as indicated in fig5 accordingly in that case instead of abutting the assembly against the lower edge of the lowermost shingle it is placed over the lowermost edge with its lower edge substantially flush with the lower.