Angled corners and joists allow you to create unique deck designs with interesting shapes. Learn how to add angled corners and joists to the deck frame with our step-by-step instructions.

metal wood deck table and chairs
Laurie Black

A deck greatly expands your outdoor living space while adding a beautiful focal point to your backyard. When building a new deck, think beyond standard square or rectangular designs to create a unique deck layout that suits your space and needs. Angled corners allow you to construct interesting deck shapes that follow the boundaries of your yard, work around obstacles such as trees and landscaping, or create more space for outdoor cooking equipment and patio furniture. Building a deck frame with angled or clipped corners also helps you avoid a boxy look by softening the edges. The angles make it more difficult to lay joists and give your deck the support it needs, but it's not an impossible task. We'll walk you through the entire process, including how to level the beams and attach angled joists. Follow the steps below to learn how to angle corners and joists when building a deck frame.

  • Working time 6 hrs
  • Start to finish 6 hrs
  • Difficulty Kind of Hard
  • Involves Carpentry Skills, Sawing, Drilling
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What you need

Tools
Materials
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How to do it

Part 1

level the beams
Step 1

Level the Beams

The joint where the two beams meet doesn't have to be tight, but the two beams must be on the same level. Wedge a shim above the post of one beam, if necessary. Drill pilot holes and drive screws or nails to fasten the beams to each other.

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mark the angled cut
Step 2

Mark the Angled Cut

Assemble the outside frame as you did when you laid out the deck, set it on the beams, and attach the rim joists to the ledger. Check for square, then anchor the rim joists to the beam with screws.

To mark the angled cut line, measure out from the corner an equal distance in both directions. Align a straight 1x4 with both measurements, and mark the header and the rim joist. Transfer the marks to the faces of the boards with a square.

cut header and rim joist
Step 3

Cut Header and Rim Joist

Use one of the temporary supports that you made for marking the layout to hold up the header; the rim joist rests on a beam. Set a circular saw at 90 degrees and cut the header and the rim joist.

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cut to fill corner
Step 4

Cut to Fill Corner

Measure between the cuts on the header and rim joist and cut an angled piece to fill the corner. Hold the angle-cut piece in place and drill pilot holes. Attach it with nails or screws.

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cut and install joists
Step 5

Cut and Install Joists

Cut and install the joists with the crowns up. Attach joist hangers at the ledger, or drive screws or nails through the header into the joists. To measure for cutting a joist at the angled section, hold it in place and mark it. Have a helper hold one end up against the ledger so that its bottom edge is close to the top of the ledger. Mark the bottom of the joist while another helper measures to see that it is parallel with the next joist. Transfer the mark to the face of the joist using a layout square, and cut at a 45-degree angle.

notch joists around steps
Step 6

Notch Joists Around Steps

If a set of concrete steps is in the way, notch the joists. Cut a joist to length and hold it in place. Level the joist. Steps often slope away from the house, so there might be a gap under the joist. Mark where the joist meets the top of the ledger. Transfer that measurement to the joist where it crosses the edge of the step. Lay out your cut line between these two points.

Because the width of the joist has been reduced, it must be reinforced. Cut a scrap piece of 2x lumber to rest on a lower step and come up nearly to the top of the joist. Attach the support to the joist with several screws.

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attach angled joist
Step 7

Attach Angled Joist

Use a special skewed joist hanger to attach an angled joist to the header. This step is necessary even if you have fastened all the other joists to the header by backscrewing or nailing.

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work around obstructions
Step 8

Work Around Obstructions

It's common for pipes, vent caps, and other obstructions to stick out of the house at about the same height as the ledger. If a vent falls at the top of a ledger, cut a notch for it. If the vent falls in the middle of the ledger, remove the vent cap and extend the duct by 1-1/2 inches. Use a hole saw to make a clean circular cut in the ledger, fit the duct through the ledger, and reinstall the vent cap.

If the obstacle is in the path of a joist, you'll have to frame around it, as shown above. Install ledger pieces on either side, taking care that the pieces are at exactly the same height. Install joists on either side of the obstacle, then cut and install a piece of blocking between the joists. Cut a joist to run from the header to the blocking piece.

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