Protected membrane roof system

1. 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 the ballast material selected from the group consisting of soil, stone and pavers;

a netting positioned over the ballast material;

at least one fastener assembly comprising:

a base seated substantially adjacent the upper insulation 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; and

a waterproof membrane positioned over the roof decking beneath the upper insulation board, the at least one fastener assembly neither penetrating nor attaching to the membrane;

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 beneath the upper insulation board positioned beneath the ballast material without compromising the waterproof membrane.

2. The system of claim 1 wherein:

the upper insulation board is further formed on the upper board bottom surface with a downwardly-opening recess substantially concentric with the through-hole; and

the free-floating base of the fastener assembly is substantially seated within the recess.

3. The system of claim 1 wherein the upper insulation board is formed having two spaced-apart through-holes.

4. The system of claim 3 wherein the upper insulation board is a nominal eight feet (8′) long and four feet (4′) wide and the through-holes are positioned so as to be approximately four feet (4′) apart and approximately two feet (2′) from each of the closest edges thereto.

5. The system of claim 1 further comprising a lower insulation board having an upwardly-facing lower board top surface and an opposite downwardly-facing lower board bottom surface, the lower insulation board positioned beneath the upper insulation board.

6. The system of claim 5 wherein:

the upper board bottom surface is immediately adjacent the lower board top surface; and

the waterproof membrane is installed directly over the roof decking so as to be beneath the lower insulation board immediately adjacent the lower board bottom surface, whereby the base of the fastener assembly is separated from the membrane by the lower insulation board.

7. The system of claim 5 wherein:

the lower board bottom surface is immediately adjacent the roof decking; and

the waterproof membrane is installed between the upper insulation board and the lower insulation board so as to be immediately adjacent both the upper board bottom surface and the lower board top surface.

8. The system of claim 1 further comprising a filter fabric layer substantially between the upper insulation board and the ballast material.

9. The system of claim 1 wherein the ballast material is soil.

10. The system of claim 9 further comprising a semi-rigid drainage retention layer substantially between the upper insulation board and the soil ballast material.

11. The system of claim 10 further comprising a filter fabric layer substantially between the drainage retention layer and the ballast material.

12. The system of claim 1 wherein the ballast material is stones.

13. The system of claim 1 wherein:

the ballast material is pavers; and

the at least one fastener assembly is positioned within the upper insulation board such that the rod extends substantially vertically between adjacent pavers.

14. The system of claim 13 wherein:

the pavers are a nominal two foot by two foot (2′×2′); and

two fastener assemblies are installed within two through-holes formed in the upper insulation board spaced approximately four feet (4′) apart such that the fastener assemblies extend between alternating pavers.

15. The system of claim 1 wherein the rod and cap are threaded.

16. The system of claim 1 wherein the rod is selectively trimmable to a desired length.

17. A protected membrane roof system for installation on a roof decking, comprising:

a lower insulation board having an upwardly-facing lower board top surface and an opposite downwardly-facing lower board bottom surface, the lower insulation board positioned over the roof decking;

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, the upper insulation board positioned over the lower insulation board;

a ballast material positioned over the upper insulation board;

a netting positioned over the ballast material;

at least one fastener assembly comprising:

a base seated substantially adjacent the upper insulation 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;

a waterproof membrane positioned above the roof decking, the at least one fastener assembly neither penetrating nor attaching to the membrane;

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 beneath the upper insulation board positioned beneath the ballast material without compromising the waterproof membrane.

18. The system of claim 17 wherein:

the upper board bottom surface is immediately adjacent the lower board top surface; and

the waterproof membrane is installed directly over the roof decking so as to be beneath the lower insulation board immediately adjacent the lower board bottom surface, whereby the base of the fastener assembly is separated from the membrane by the lower insulation board.

19. The system of claim 17 wherein:

the lower board bottom surface is immediately adjacent the roof decking; and

the waterproof membrane is installed between the upper insulation board and the lower insulation board so as to be immediately adjacent both the upper board bottom surface and the lower board top surface.

20. A protected membrane roof system for installation on a roof decking, comprising:

a lower insulation board having an upwardly-facing lower board top surface and an opposite downwardly-facing lower board bottom surface, the lower insulation board positioned over the roof decking;

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, the upper insulation board positioned over the lower insulation board;

a ballast material positioned over the upper insulation board;

a netting positioned over the ballast material;

at least one fastener assembly comprising:

a base seated substantially adjacent the upper insulation 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; and

a waterproof membrane installed directly over the roof decking so as to be beneath the lower insulation board immediately adjacent the lower board bottom surface, whereby the at least one fastener assembly neither penetrates nor contacts the membrane, the base of the fastener assembly being separated from the membrane by the lower insulation board;

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 beneath the upper insulation board positioned beneath the ballast material without compromising the waterproof membrane.