Attics are generally covered in batting or blown insulation.
How to floor an attic over insulation.
1 put on work gloves safety glasses and a dust mask before entering the attic.
With a finished attic insulation must help keep the attic areas comfortable.
Ensuring adequate insulation under the flooring.
The joists for this riser should run perpendicular to the existing ceiling joists.
This of course would preclude using the area for.
If blown in insulation is used control the height or thickness of the layers so boards can by laid over top without having to compact the filler.
However if you keep the storage weight to a minimum you may be able to build a storage platform above the insulation by attaching supporting beams to the sides of the trusses.
Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target r value and to prevent thermal bridging the heat loss that occurs through the wood framing.
Build up the height of the joists prior to installing flooring when the insulation reaches the tops of the joists.
Even easier you can also use a prefabricated attic floor kit designed specifically to raise the attic floor above the insulation.
Place flooring over insulation to make your attic space functional.
In zones 4 through 8 if you have full height insulation over 100 of the ceiling including the top plates as shown in your excellent guide here the iecc allows r 38 rather than the r 49 that is required if you can t achieve full depth insulation over 100 of the attic floor.
How to insulate a finished attic.
To give yourself enough space to ensure adequate insulation under the flooring construct a riser of 2 x 4 s in the attic over the existing joists.
A finished attic should be insulated much like the rest of the house with insulation in the walls and ceiling.
By adding the boards you increase storage space for items not needed.
Without removing the flooring you have the option of blowing loose fill insulation fiberglass or cellulose fiber over the top of the floor.
This will make the installation of these new joists easier.
Work from the perimeter of the attic toward the door or hatch so that you don t trample all over the insulation you just put in.