Hip Trusses

Hip roofs with various truss applications can be modeled, including step down hip trusses, sub-girder hip trusses, and drop hip or California trusses.

Step Down Hip

In the illustration below, the flat-topped trusses are called hip trusses. Alternating hip trusses are colored differently to improve visibility.

To create a step down hip truss system

First, draw a Roof Truss

at the apex of the triangular hip roof plane. It will snap exactly into position.

Select the truss; click the Multiple Copy edit button; and click and drag the Move handle down into the hip to create copies at regular intervals. See "Copying Trusses".

Stop when the height of the hip truss reaches a reasonable minimum.

Using the Roof Truss

tool, draw hip jacks along the hip ridge from the last truss out into the overhang.

Using the Roof Truss

tool, draw a jack truss from the intersection of the last hip truss and the hip jack to the eave.

Select the jack truss; click the Multiple Copy edit button; and lay out jack trusses up to the other hip jack.

Subgirder Hip

Subgirders are the partial trusses that butt into the doubled truss at the end of the main run. In the following illustration, the double truss has one face colored dark gray, and several subgirders are colored light gray.

To create a subgirder truss system

Draw a Roof Truss

where the hip apex meets the ridge.

Double it by drawing a second truss on the far side from the hip section.

Using the Roof Truss

tool, draw the first subgirder from the hip apex out to the eaves.

Select it and using the Multiple Copy edit button, make copies in both directions. Stop when the height of the subgirders reach a reasonable minimum.

Finish off with hip jacks and jack trusses as in a step down hip system.

Drop Hip

A Drop Hip, or California Hip, system uses drop hip trusses to support stick frame hip ridges and common rafters.

Two of the drop hip trusses are colored gray to help distinguish them. Notice that the common rafters are supported by the drop hip trusses.

To create a drop hip truss system

Start a drop hip truss system as you would a step down hip system.

When the hip trusses are drawn, group select them; open the Truss Specification dialog; and select the Drop hip truss check box.

Use the Build Framing dialog to produce the common rafters, and the short joists at the hip end.

Advantages and Disadvantages of the Different Hip Systems

Each of hip roof method has its advantages. With both the Step Down hip and the Subgirder hip systems, you can get almost everything you need from the truss company. You will need to get small corner jack and end jack trusses in addition to the larger trusses.

With the Step Down hip, if the hip trusses are placed according to your standard on center spacing, the space measured down the hip between the trusses is larger than the standard.

With the subgirder system, spacing measuring down the roof sections on either side of the hip, near the hip is too large.

The Drop Hip system eliminates the spacing problems because the roof sheathing is nailed to common rafters that pass over the drop hip trusses. The disadvantage to this system is that it requires the rafters in addition to the trusses, and with a shallow pitch roof the drop hip truss may not be deep enough to give sufficient strength.

The first two methods normally require blocking along the hip ridges. The third uses a continuous hip ridge rafter as well as common rafters that run over the drop hip trusses. Blocking and rafters can be drawn in manually, but are often supplied by the automatic framing generator. See "Mixing Trusses with Stick Framing".