A 2-ply SBS modified bitumen roofing system consists of:
Roof deck Most modern homes have a roof deck of plywood, but some older homes have decks made from boards (or planks). In re-roofing applications the roof deck sometimes requires repairs to rotten wood in order ensure a proper substrate to accept the roofing system. It may also require re-sloping to provide positive drainage to drains, scuppers, or eavestroughs.
Vapour Barrier A vapour barrier is required if insulation is to be installed over the roof deck.
Insulation Most homes in Canada have fibreglass insulation installed under the roof deck, so installation of a vapour barrier and additional installation on top of the roof is commonly not recommended. If additional insulation is desired by the homeowner, it can be installed from the roof by removing the deck to allow access to the airspace underneath, and replacing the deck once additional insulation is installed. Insulation can be installed over the roof deck, however, this is not common in residential applications.
If external insulation is required, the most cost effective and highest performance type insulation in terms of Long Term Thermal Resistance (LTTR) per inch of material is polyisocyanurate insulation. More commonly known as polyiso, it is a rigid foam board insulation that provides an LTTR of 5.6 to 6.0 per inch of thickness, depending on the manufacturer.
Protection board A protection board is required to be installed over the roof deck (or over insulation if installed) to smooth out the surface in preparation for the waterproofing membranes, provide additional support over the previous layer, and for flame protection if the base layer is to be torch applied.
Base Layer The base layer is the first layer of SBS modified bitumen material. The material comes rolls with a width of 1 meter, and is installed in overlapping strips to cover the entire field area of the roof. Base layers can be embedded in hot tar, torch applied, or adhered to the protection board. If the base is adhered, a special primer must be applied to the protection board to ensure a strong bond with the adhesive on the underside of the base membrane. Alternately, a manufacturer approved protection board can be used with a surface that provides excellent adhesion without the need for primer.
Toronto Roofing Industries recommends an adhered base for residential applications because it provides an extra layer of flame protection prior to installing any membranes with the torch method.
Granulated Cap Layer The cap layer is the final waterproofing membrane in the system. It is comprised of SBS modified bitumen layer that is covered with coloured granules that protect the waterproofing material from harmful UV radiation, and provide mechanical protection from foot traffic. The material comes in 1 meter wide rolls, and is applied in strips over top of the base layer. The overlapping seams are positioned staggered at least 6″ from the seams of the base layer. Cap layers can be embedded in hot tar, torch applied, or adhered to the base layer.
Toronto Roofing Industries recommends a torch applied cap for residential applications because it is the most straighforward and fool-proof method for achieving a perfect seal with the base layer. All of our roofers who perfom torch work carry valid propane licenses and are factory trained on the correct installation methods for torched cap membranes. All our crews operate under a comprehensive safety policy that includes regular safety training and a never ending focus on safety for our workers and customers. Toronto Roofing Industries is fully insured against fire damage for all hot-applied methods.
Flashings Flat roofs have penetrations such as plumbing stacks, breathers, furnace vents, and drains. They also instersect vertical surfaces such as curbs that support air conditioners, and parapet walls. Every edge of a roof must be flashed with the appropriate combination of base membrane, cap membrane, and metal flashing to ensure that no leaks occur at any edge over the full life of the roofing system. Flashings must be installed according to manufacturers’ specifications in order for the material warranty to be valid.