How to Angle Corners and Joists

Angled corners and joists allow you to create unique deck designs with interesting shapes. A deck not only makes your backyard more visually appealing but also significantly increases the amount of area you have available for outdoor enjoyment. When constructing a new deck, look outside the box of the typical square or rectangular designs and come up with an original deck concept that is tailored to your living space and requirements. You can construct intriguing deck shapes by using angled corners, such as ones that follow the boundaries of your yard, work around obstructions such as trees and landscaping, or create additional space for outdoor cooking equipment and patio furniture.

Read more:  How to Build a Raised Deck

By building a deck frame with angled or clipped corners, you may avoid giving the deck a boxy appearance and soften the edges at the same time. It will be more difficult to lay the joists and provide the necessary support for your deck because of the angles, but it will not be impossible to do so. We will guide you through the entire process, including how to install angled joists and level the beams. In order to learn how to angle corners and joists when creating a deck structure, follow the procedures that are provided below.

Read more: Rooftop Deck Construction 

Level The Beams

There is no requirement for a particularly tight fit at the point where the two beams connect; nonetheless, the beams themselves must be at the same level. If it is necessary, place a shim on top of the post that supports one of the beams. For the purpose of securing the beams to one another, drill pilot holes and then drive in screws or nails.

Read more:  How to create a Herringbone Decking Pattern

Mark The Angled Cut

Assemble the perimeter frame in the same manner as you did when you were laying out the deck, place it atop the beams, and fasten the rim joists to the ledger. First ensure that everything is square, and then use screws to secure the rim joists to the beam.

First, measure out from the corner an equal distance in both directions to determine where to mark the angled cut line. Mark both the header and the rim joist once you have aligned a straight 1x4 with both of the measurements. Utilizing a square, transfer the marks onto the respective faces of the boards.

Read more:  How to Build a Freestanding Deck

Cut Header And Rim Joist

It is recommended that you make use of one of the temporary supports that you constructed in order to outline the layout in order to hold up the header. The rim joist is supported by a beam. Cut the header and the rim joist using a circular saw with the blade set at a 90-degree angle.

Cut To Fill Corner

Take the distance between the cuts made on the header and the rim joist, and then use that measurement to guide the cutting of an angled piece to fill the corner. Drill pilot holes while holding the piece that has been cut at an angle in place. Nails or screws can be used to secure it.

Cut And Install Joists

Joists should be cut and installed with the crowns facing upward. Hangers for the joists can be attached to the ledger, or screws or nails can be driven through the header and into the joists. Hold the joist in place while you make a mark on it to get the measurement for cutting it at the angled part. Have a helping hand hold one end up against the ledger so that its bottom edge is nearly level with the top of the ledger. While one of your assistants measures to ensure that it is parallel with the following joist, you should mark the bottom of the joist. Make a cut at a 45-degree angle after transferring the mark that you made to the face of the joist using a layout square.

Notch Joists Around Steps

Notch the joists if you need to go around a set of concrete stairs that are in the way. Adjust the length of a joist, then secure it in position. Level the joist. Because steps often slope away from the house, there may be an empty space under the joist in the area. Make a mark at the point where the joist and the ledger meet at the top. This measurement should be transferred to the joist at the point where it spans the edge of the step. Create a line of cut between these two locations using your cutting tool.

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The joist has to be reinforced as a result of the fact that its width has been decreased. Remove a piece of scrap 2x lumber and cut it so that it may rest on a lower step and come almost all the way up to the top of the joist. Put a few screws through the support and into the joist to secure it.

Attach Angled Joist

When attaching an angled joist to the header, a specialized skewed joist hanger should be utilized. Even if all of the other joists have been secured to the header by using back screws or nails, you still need to complete this step.

Work Around Obstructions

It is not uncommon for impediments such as pipes, vent caps, and other fixtures to stick out of the house at a height that is about equivalent to that of the ledger. If a vent is located at the top of a ledger, a notch should be made to accommodate it. If the vent is located in the middle of the ledger, the vent cap should be removed and the duct should be extended by 1-1/2 inches. First, create a clean circular cut in the ledger with a hole saw. Then, thread the duct through the ledger and replace the vent cover.

You will need to frame around the impediment if it is in the way of a joist, as was demonstrated in the prior image. Ledger pieces should be installed on either side, taking care to ensure that all of the pieces are at the exact same height. Put joists in place on either side of the obstruction, and then cut and set up a piece of blocking in the space in between the joists. Remove a joist from the header that will run all the way to the blocking piece.

Faqs About Angle Corners and Joists

What’s the simplest way to create a 45° “clipped” deck corner?

• Square the frame, mark equal offsets along the two sides, connect the marks, cut the rim and header, then add a small angle “filler” piece to close the corner before running the joists. 

How do I support joists that hit a header at an angle?

• Use skewed joist hangers (right/left) or field-skewable hangers rated for your angle; follow the hanger’s nailing pattern and notes (some require bevel-cut joists).

Do diagonal/angled deck boards change joist spacing?

• Yes. Most brands call for 16 in. o.c. when boards run perpendicular, and 12 in. o.c. when boards run at ≈45°. Also ensure boards bear on ≥3 joists.

How do I lay out an accurate clipped corner?

• After squaring the rectangle, measure equal distances from the corner along both edges (e.g., 24" and 24"), snap a line between marks, and cut. This keeps the new edge bisecting the corner.

Any code limits on notching or drilling joists for angled work-arounds?

• Yes. IRC R502.8 / R502.8.1 strictly limits notch depth/locations and hole spacing; avoid notches in the middle third of span and keep to the one-sixth/one-third rules. Don’t notch to “force” an angle—frame it properly.

What’s the right blocking for picture-frame borders at angled corners?

• Install extra blocking/added joists to support the border and mitered corner, typically 16 in. o.c. or tighter, with flat blocking under the miter. Many guides show double- or triple-picture-frame blocking schemes. 

How big a miter gap should I leave at composite picture-frame corners?

• Follow your brand’s gap chart; many composite guides call for a small expansion gap at 45° miters to accommodate movement. (Example guidance shows a few millimeters.) Use the manufacturer’s fastening pattern.

What tools/blades give clean angled cuts in composites?

• A fine-tooth carbide miter saw blade (≈60T+) is commonly recommended for composite/PVC decking; support long cuts and cut slowly for clean miters.

Do angled corners or diagonal decking change beam/joist loads?

• They can—diagonal layouts and cut corners shift load paths and may need added trimmers/headers or tighter spacing. Complex decks often require engineered details for point loads and cantilevers.