Before assembling your Therma-Dome cover, read and understand these instructions completely.

Make sure there is enough headroom in the space above the attic stair opening for the completed Therma-Dome cover to fit through the opening. If the opening is obstructed, the assembly must be done in the attic. A flat, solid work surface is preferable.

All Therma-Dome parts are lap-jointed for a precise fit, and should have a continuous ¼" bead of adhesive applied to the center of each joint as you assemble your Therma-Dome cover.

Part "A"
End pieces
(short, with Velcro® strap and gasket)
Part "B"
Side pieces
(long, gasket on one edge)
Part "C"
Top pieces
(long, no gasket)

Always hold the pieces securely by the thickest part of the board to avoid breakage of the component.
Do not hold pieces by the narrow part of the board as breakage could occur.


Step 1:

Apply the adhesive to both short lap-jointed end pieces (Parts "A"). Asemble the ends and the sides (Parts "A" and "B") together. Make sure all parts are tight and the edges are even. Use 3" lengths of foil tape to secure each of the four corners while the adhesive dries.

Step 2:

Apply the adhesive to the top edge of the assembled sides. Apply adhesive to the lap joint between the top pieces (Parts "C") as you fit them into place. Apply 3" lengths of tape to hold the components in place while the adhesive dries.

Step 3:

The finished appearance of the Therma-Dome may be improved by applying the remaining foil tape to all joints of exposed edges. Note: This is for appearance only, the adhesive is the primary bonding agent. The tape may also be used to repair or patch your Therma-Dome should it become damaged.



For the best results, the Therma-Dome must be resting on a solid surface. If your attic does not have a solid floor, install a level deck (plywood, OSB, or equivalent) at least 8" wide around the rough opening of the attic staircase.

In the rare instance where the rough opening of the stair is a little larger than the inside dimension of the cover, nail a furring strip to the inside of the opening, even with the attic floor. Use caulk to ensure air-tightness.


Center and nail the anchors to each end of the stairway opening so that the Therma-Dome can be secured in place over the attic opening using the Velcro® straps that are attached to Parts "A".