When using plywood nail it directly to the purlins and screw the metal roofing panels through the plywood into the purlins as instructed by the manufacturer.
Installing metal roofing panels over plywood.
Align the first metal roofing panel so that it overlaps the edging by 1 2 to 3 4 of an inch and is square to the roof line.
If you are placing metal panels over an existing roof you still use purlins.
Ensure that the plywood deck is strong enough to withstand the added weight of the metal panels.
The purlins not only give you something other than the existing roof to accept the roof panel fasteners they also create an airspace between the roof panels and the existing roof.
I have removed all the old shingles from the roof boards not plywood the roof is in great shape and have installed an ice shield over the roof.
This is by far the most common way to install a metal roof.
Continue installing the metal panels making sure that the edges overlap at least 1 in 2 5 cm or as required with the adjacent panel.
The purlins support the panels.
Do this until the entire roof is covered.
Be sure the larger edge is laid so that the small edge of the next panel will overlap it.
Install waterproof felt over the plywood to add protection against moisture.
The plywood should be clean and free of raised nail heads to provide a uniform deck structure for the metal.
3 install 1 4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1 4 purlins over the shingle roof.
To secure it measure it roll it out over the plywood cut it to the dimensions of the roof with a roofing or utility knife and finally hammer it securely to the plywood with 1 2 inch roofing nails.
Can i install the metal roof over the ice shield or do i need the 1 x 4 battens every 2 feet as well it s a low slope roof thus the ice shield for extra protection.
In this installation the vapor barrier is installed on the side of the insulation nearest the interior of the building.
On top of this underlayment goes a slip which protects the material from tearing as the metal roof expands and contracts with changing weather.
Energy efficient and available in a variety of colors that will.