The great advantage of doing a project yourself is that you’ve got complete control to make sure the job is done correctly. And when it comes to rough framing, you can’t overstate the importance of a job well done. When building a home, adding a room or just adding a wall, rough framing creates the skeleton of your home, and attention to detail will pay off in the long run.
One of EHT‘s readers recently inquired about recommended methods of framing a corner on a new room addition. This article will focus on corner framing techniques that not only stand strong structurally, but also take into consideration often overlooked aspects of rough framing, such as wiring and insulation.
Interior 90-degree Corner
When framing a wall corner, the two initial factors to consider are structural integrity and providing a good nailing surface for the interior sheathing and/or wall covering. One standard method often used for interior wall corners is called the “three-stud corner.” In this case, the corner is constructed of three studs nailed together or two studs sandwiching blocking that functions as a spacer.
At the end of the wall where you began your layout, nail the three studs together and install into the wall as you assemble it on the floor. Secure all corners together with 16d nails every 16 inches, nailing the boards flush on all surfaces. At the opposite end of the wall, where the plates are 3 1/2 inches shy of the edge of the foundation (because of the overlapping walls), place a single stud.
This method provides the adequate structural integrity for the wall, but it also creates a solid block of wood at the corner that isn’t very friendly to the process of installing electrical wiring. If wiring is to be routed through the corner, sandwich blocking between the two corner studs. The spaces between the blocking leave enough room to drill holes and run cables through the corner more easily.
Alternative Interior Corner
Not all corners are created equal. Sometimes it’s hip to be square, but other times you might want to take a new angle on things.
Corners that aren’t square can be constructed of studs that are installed 90 degrees to the respective top and bottom plates of the two intersecting walls (see diagram #2). The studs will meet on the inside of the smallest angle of the corner. The top and bottom plates extend beyond the studs, and are cut to meet flush at the intersection of the walls. The top plate is doubled, with one of the second plate layers extending beyond the seam of the first top plates and cut to be flush with the edge of the studs.
This method creates a gap between the wall studs on the opposite side of the corner. The gap formed from this angle provides a poor nailing surface where the wall covering will intersect. This is often overlooked by “framers on the run,” but should be addressed by the competent DIY’er.
Rather than leaving this gap and simply hiding it with wall covering, miter two additional studs to fit into the gap, adding additional strength and a proper nailing surface for the wall covering.
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.