Notes:
SLIDE NO.11 - UNDERLAYMENT
The first step is to install an insulation board which is typically mechanically fastened onto the existing roof deck.
The next step is to install a ridged underlayment which is adhered with hot asphalt.
New roofs are designed using a modified bitumen membrane system.
This system consists of a minimum three layers of roofing materials using a fiber glass reinforced base sheet.
The roofing layers are applied over a roof insulation system that is generally tapered in order to achieve the required new roof slopes.
The tapered insulation boards are placed over the roof deck. Then a ridged underlayment board is placed over the insulation boards.
The modified bitumen membrane roof system is adhered with hot asphalt between the layers.