The illustration shows two layers of osb or plywood roof sheathing.
How to fit exterior roof insulation boards.
Cut panels on roof before doing any work with the metal roof insulation you should have it brought up onto the roof.
Nail metal flashing along the edges of the roof line.
That said some gba readers install r 60 attic insulation and you re free to do that if you want.
Stagger the joints to ensure a uniform roof surface.
Here is how we cut and fit our pir insulation to insulate the walls and roof of the house.
Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.
This reduces the need to go up and down the ladder for tools pieces of insulation and making measurements.
Align the insulation boards with the chalk lines and lay them onto the deck.
Remove existing roofing and non adhered underlayment to expose roof sheathing.
How to put rigid foam insulation on the roof before putting on shingles.
To save a step i would recommend using a nailbase panel foam preadhered to osb or sometimes plywood on one side only see photo facing page.
More insulation on the exterior is good.
Make all cuts to the foam panels on the roof for more accurate cuts and quicker placement.
Put on your roofing safety harness and secure the safety rope to the top of the roof.
Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams.
This technique is the same for all rigid insulation such as kingsp.
But putting insulation above the roof sheathing is misguided if you have a vented attic.
Instead of adding insulation above your roof sheathing put it on the attic floor where it belongs.
Trim the boards to fit as.
Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing.
A lower layer conventionally nailed to the rafters and an upper layer installed as a nailing surface for the roofing material on top of the rigid foam.