Closed cell polyurethane foam insulation is sprayed around the new roof frame sealing edges and providing support for the rafters and the ridgeboard.
													
																	Framing a new roof over an old roof. 
									
	
		
	
																	A new level 2 6 ridgeboard and rafters then are assembled over the old roof and are attached to the existing structure with nails and lag screws driven into the underlying wall top plates. 
																	Use 1 5 or 1 75 inch roofing nails. 
																	Your second row of shingles should be cut to 10 inches wide. 
																	Installing the new roof. 
															
													
									
	
		
	
																	You can frame a new roof over the old but it will need to be designed for the span and pitch. 
																	The sheathing must be stripped from the old roof for a couple feet along the bottom to get the new ceiling joists in.