October 29, 2019

How to handle Inside and Outside Corners

Inside Corners Corners that form an inside angle	Outside Corners Corners that protrude into a room

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We recommend starting an InSoFast project on an inside corner

Important: some steps of this process will involve applying adhesive directly to a panel’s foam surface. We strongly recommend using PL Premium 3X Stronger Construction Adhesive for this purpose. This glue has been tested to work with the EPS foam.

Inside Corners

Corners that form an inside angle

Cut the first panel about ¼” less than the actual measurement needed so that the panel is not tight to the corner. Turning the corner, the next panel should fit snug against the first panel.

Outside Corners

Corners that protrude into a room

These corners need a metal corner bead attached to them. If necessary, mark and cut the first panel flush with the corner. You will use the cut off piece, or a new panel, to wrap around the other side of the corner.

Install the first panel flush with the corner edge of the concrete wall making sure to place a solid-backing bead of adhesive near the edge of the cut. On the cut-off piece or second panel run two beads of adhesive. The first bead, running approximately 1″ from the edge, will bond the foam of the InSoFast panels together at the corner. The second bead, running approximately 3″ from the edge of the panel, will bond the foam of the InSoFast panel to the concrete.

Video for Corner attachments

Utility angle or light gauge metal “L” angle.

The metal angle is used if attachment in the solidly backed corner is desired. The metal angle screwed together forms a solid corner in which to apply your finishes.

Attaching Drywall to Panels around Inside Corners

Recommended: Ensure that your cornered UX panels are solid-backed by running a bead of adhesive along the panel (foam or stud) 2″ from the corner. Just before installing drywall, place a bead of adhesive on the foam near the corner. The drywall is bonded to the foam and the foam has been bonded to the concrete.
Option 1: When installing drywall, float the corners by screwing drywall into nearest attachment studs. This is a common practice for professional drywall installers because the InSoFast panels provide solid backing for the drywall.
Option 2: Place a bead of adhesive approximately 1″ from each side of the corner. Press 2″ x 2″ – 25 ga. sheet metal angle into adhesive. Attach drywall by screwing into the metal corner angle.

Securing Drywall at Outside Corners

1. Use a metal corner angle (3″ x 3″, 25ga sheet metal) to wrap outside corners. Generally available in the roofing/flashing section of home improvement stores or drywall supply yards.
2. Place a bead of adhesive approximately 1-2″ from each side of the corner. Press 25 ga. sheet metal angle into adhesive.
3. Hang drywall by screwing all-purpose drywall screws into the InSoFast studs and into the sheet metal corner angle. Install a second metal corner angle over the drywall using all-purpose drywall screws.

Drywall Fire Code and Alternatives

Important: InSoFast panels are manufactured using a flame retardant foam and are classified as rigid foam plastic insulation. They fall into the same class as pink, blue and yellow insulation boards which are required by code to be covered by ½” drywall or any other approved 15-minute thermal barrier (IBC 2603.4). If choosing an alternative to drywall it is important to check with your local building code official to make sure it meets your local requirements.

Stem or Partition Walls

Partition walls can be mechanically (screwed) to the panel’s stud or adhesively attached to the foam.

Attaching Intersecting Walls

Turning Corners