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A Smart Way to Frame a Corner

Construction How-To, Framing, walls April 1, 2004 Matt Weber

This wide-angle corner is built with mitered supports.

This wide-angle corner is built with mitered supports.

Again, this process will create a thick block of wood that, while very strong, creates a thick obstruction for running any sort of electrical wires. If the wall is intended to house any wiring, use mitered blocking installed in the gap rather than continuous mitered studs. This will allow space to more easily drill holes and install cables, while still providing a proper nailing surface.


Exterior 90-Degree Corner

One common framing error when constructing a wall is overlooking the importance of insulation in small gaps created from framing the corners of exterior walls. Wood itself doesn’t do a good job insulating your home, and untreated gaps allow Mother Nature to intrude through these nooks and crannies, which will ultimately be reflected on your energy bill.

On a 90-degree exterior corner, the “three-stud” method doesn’t allow adequate space to install insulation. To accommodate this, install single studs at the very end of each wall. The first stud will cap the outside of the exterior wall, while the stud of the intersecting wall will be installed perpendicularly adjacent to the first “capping” stud (see diagram #3). Nail together these intersecting studs with 16d nails every 16 inches.

Next, you’ll need to strengthen the corner with a third stud while still allowing space to add both insulation and any electrical wiring. On the interior edge of the wall with the exterior “capping” stud, install a third stud parallel to the stud on the intersecting wall.

Rather than crowding this third stud flush in the corner of the wall, install it approximately 1 inch away from the “capping” stud. Toe-nail this third stud to the second stud of the corner. This creates a 1 inch gap that allows easier installation of electrical wiring as well as spray-in or closed-cell foam insulation, which works nicely in small spaces. This corner treatment creates a strong intersection while remaining functional for the installation of the other amenities. Plus, this provides a solid, nailable surface for the wall covering on both the interior and exterior sides of each wall.


Alternative Exterior Corner

When adding window alcoves, hexagonal room additions or any other out-of-square corner at an exterior wall, you will again face the gap created behind the intersecting studs. Rather than installing solid studs or blocking, fill the corner gap with spray-in or closed-cell foam insulation.

Cut or spray insulation into the corner to weatherproof the interior of your home. When installing the insulation, trim it about an inch shy of being flush with the corner studs on the exterior side of the wall. Then use the leftover space to cover the insulation with 1-by-4 or 1-by-3 boards cut to fit each side of the intersection (see diagram #4). The 1-by-4′s will run from top plate to bottom plate. This provides a strong, insulated corner, navigable for the installation of electrical wring, while also providing a solid nailing surface at the edges of each corner, on both the interior and exterior sides of the corner.

The Extra Effort

The insulation of corner gaps and providing a solid nailing surface is often overlooked by professional framing crews who throw up walls and ceilings on a daily basis. It takes some extra time and effort to properly construct a strong, insulated corner. But the extra effort means the sheathing can be installed more sturdily. And the insulation will help protect against heat loss and minimize cooling costs. These techniques for building a corner are the best bet for those extreme DIY’ers who insist on building it themselves, and building it better.

A Few Framing Tips

  • You might find it helpful to assemble the wall on the floor, nail it together, and then raise it into place. Work on a level surface to help lay out the walls flush. Try to avoid assembling walls on the ground, and keep the work surface clean and free of obstructions.
  • Lay out the top and bottom plates on edge, inserting the wall studs between the plates and nailing them in place at the ends of the studs.
  • Check for squareness by measuring diagonally from each corner after each wall is assembled.
  • At 90-degree corners, once the sheathing is installed and the wall goes up, the end of one wall will cover the corner of the other.