Roof tops: Two basic types of roof systems are commonly found in the US and Canada for retrofit and new roofing. Roofsystems that specify insulation below the waterproofing layer, and roof systems that have extruded insulation above the waterproofing membrane.
Roof Type 1 – Common Insulation installed below Roof Membrane: Currently the most typical and common roofing systems specify roofing membranes be installed over common rigidinsulation boards that are typically manufactured from poly-isocyanurate, perlite, or wood fiber-board materials. These typical systems incorporate 20 psi density insulations that need additional support to create an adequate bearing surface. That is typically accomplished in one of three ways:
- Incorporate one of the thin Cap Bearing Protective Layer Insulation specifications that call for a very thinprotective layer to be installed on top of the common 20 psi insulation. Such a cap type insulation product is commonly formed as a thin dense low-foamed isocyanurate layer, and provides the necessary pedestal support.
- Bison Model FIB Pedestal Base: Install an enlarged base that supports the pedestal to distribute the anticipated loaded weight of a pedestal over an enlarged area. Bison manufacturers the Floating Insulation Base (Model FIB) for this purpose. Model FIB is specifically designed to be directly installed over Type 1 roof systems that incorporate 20 psi common insulation boards.
- Insulation above the Membrane: Install a 1.5” thick (min.) layer of dense, closed cell 40 psi (min.) extruded cell poly-styrene insulation board above the common roofing system that has buried insulation to provide support for the pedestal system.
Roof Type 2 – Closed Cell Insulation Protecting Roof Membrane Systems: Inverted Roof Membrane Systems that incorporate 40 + psi density closed cell extruded poly-styrene insulation on topof the roofing membrane are the second type. The dense extruded polystyrene is capable of bearing Bison pedestal weights. Before the ballast rock is installed, deck system pedestals can be installed directly on the insulation. Varying densities and thicknesses of extruded polystyrene are commonly used, and substantial ballasting is required.Bison pedestals can be installed directly on top of gravel removed 40 psi, or greater, extruded closed cell polystyrene insulation with 1.5” thickness or greater.
Decks on Grade: Any substrate soil that is to receive pedestals shall be adequately compacted and have positive drainage slope. A “walkway gravel” base (i.e.: 1⁄4” Minus (breeze) should be installed and compacted at Bison Deck Support locations. Bison Floating Foundation Bases (FFB) must be used beneath all on-grade Bison Deck Support decks. Level the surface and install directly on grade as a base. A wall or perimeter containment on all open sides is required. Install structural perimeter containment that restrains the entire decking system.
Stone Deck Innovations can help you transform your old deck into a beautiful, unique and maintenance free stone living space. Contact us today!