A method includes providing a production line configured for continuous fabrication of polymer or predominantly polymer roofing boards by setting and expansion of precursor materials on a conveyor. A first polymer or predominantly polymer material foam precursor is dispensed to the production line, and allowed to rise and at least partially set to form a foam core layer for an insulation board, the foam core layer for the insulation board having a first density. A second polymer or predominantly polymer material foam precursor is dispensed to the production line and allowed to rise and set to form a core layer for a cover board, the foam core layer for the cover board having a second density greater than the first density. The combined thickness of the foam core layer for the insulation board and the core layer for the cover board is set by constraining the expansion of the combined foam precursors using a downstream forming conveyor disposed above the rising foam precursors.

The disclosure relates to a thermal and/or acoustic insulation system as waterproofing for a flat or flat inclined outside surface of a building, especially for a flat roof or a flat inclined roof, consisting of at least one insulation element made of mineral wool, preferably made of stone wool, and having a major surface, and a lining element consisting of at least a first layer made of lining material and a second layer made of a glue activatable by heat and oriented to the major surface of the insulation element, whereby the major surface of the insulation element is free of protrusions, especially flights, and cavities thereby being planar and whereby the area connection between the insulation element and the lining element is at least 70%, preferably at least 80% of the major surface area of the insulation element.

According to one aspect, a roofing system comprises a plurality of insulation boards adapted for overlying a roof deck to form a layer of insulation. Each of the plurality of insulation boards has opposing planar surfaces and has a facer on at least one planar surface, and each of the plurality of insulation boards comprises polyisocyanurate foam having a first polyisocyanurate foam density. The roofing system further comprises a plurality of cover boards adapted for overlying the layer of insulation. Each of the plurality of cover boards has opposing planar surfaces and has a facer on at least one planar surface, and each of the plurality of cover boards comprises polyisocyanurate foam having a second polyisocyanurate foam density greater than the first polyisocyanurate foam density. The greater polyisocyanurate foam density provides for a compressive strength to resist deformation.

A protected membrane roof system for installation on a roof decking comprising an upper insulation board having an upwardly-facing upper board top surface and an opposite downwardly-facing upper board bottom surface and at least one through-hole communicating therebetween, a ballast material positioned over the upper insulation board, a netting positioned over the ballast material, and at least one fastener assembly having a base seated substantially adjacent the upper board bottom surface, a rod extending substantially vertically from the base of sufficient size so as to extend through the through-hole of the upper insulation board, the ballast material, and the netting, and a cap engaged with the rod above the netting, whereby the wind uplift resistance of the protected membrane roof system is improved and scour of the ballast material is reduced by effectively anchoring the netting to the upper insulation board beneath the ballast material.