Roof Trusses: Parts, Types and Designs

What a roof truss is

The Structural Building Components Association, the truss industry’s trade body, describes roof trusses as engineered pieces of lumber connected by metal plates to form a web that supports the roof. The strength comes from triangles: a load on any joint is shared out through members that are pushed or pulled along their length rather than bent.

SBCA sorts trusses into two basic types. The pitched or common truss is triangular and is the usual roof truss. The parallel chord or flat truss has parallel top and bottom chords; it is mostly used for floors but also on low-slope roofs. Everything else is a variation on these two, shaped for a particular roof line or ceiling.

Parts of a roof truss

• Top chord: the sloped members that form the roof plane and carry the sheathing.
• Bottom chord: the member along the ceiling line, which ties the two sides together.
• Webs: the members between the chords that form the triangles.
• Panel point: any joint where webs meet a chord; the panel length is the distance between two of them.
• Truss plate: the toothed metal connector plate pressed into the lumber at each joint.
• Heel: the end of the truss where the top and bottom chords meet over the wall; its depth is the heel height.
• Peak: the highest point, where the top chords meet.
• Overhang and cantilever: an overhang is top chord extending past the wall; a cantilever is the truss itself extending past a bearing.
• Bearing and span: the bearings are where the truss sits on walls or beams, and the span is the distance between the outer ones.
• Continuous lateral brace: a brace running across several trusses to stop webs or chords from buckling sideways.

The pitch of the top chord, the span and the heel height fix the outside of a truss. The webs, lumber sizes and plates are the designer’s job.

Common roof truss types

A common truss is named for its web pattern. SBCA lists the king post, fan, Fink and Howe as examples and notes that the chord size and web configuration are set by the span, the load and the spacing, so the same roof could use different patterns depending on the design. The four patterns:

King post truss

One vertical web from the peak to the middle of the bottom chord. The simplest common truss, used on short spans.

Fink (W) truss

Webs in a W from the bottom chord third points up to the peak and the middle of each top chord.

Howe truss

Vertical webs with diagonals running from the middle of the bottom chord up toward the heels.

Fan truss

Several webs fanning up from each bottom chord panel point to the top chord.

Truss shapes for different roofs and ceilings

Beyond the common triangle, trusses can be built to almost any outline. These are the shapes from SBCA’s list of configurations that a house is most likely to use:

Scissor truss

A bottom chord that slopes up toward the middle for a vaulted or cathedral ceiling. SBCA says the bottom chord pitch is usually half the top chord pitch.

Mono truss

A single slope with a vertical member at the high end, for sheds, porches, additions and farm buildings, or in pairs over a center bearing.

Attic truss

Room-in-attic trusses leave a rectangle open between the webs for a room or storage, with the bottom chord sized for floor-type live loads.

Gambrel truss

A steep pitch at the walls breaking to a low pitch near the peak, the barn shape. The height leaves room for webs or an attic room.

Hip truss

A flat-topped truss used in sets that step down toward each end wall, so the roof slopes on all four sides.

Dual pitch truss

A different pitch on each side, for example a steep face for snow or more roof area for solar panels on one side.

Piggyback truss

A flat-topped base truss with a small cap truss on top, used when one truss would be too tall to build or ship.

Parallel chord truss

Flat top and bottom chords. Mostly a floor truss, but also used on low-slope roofs.

Vaulted parallel chord truss

Top and bottom chords at the same pitch, made possible by a raised heel, for a steep vaulted ceiling.

Tray truss

A bottom chord that slopes up a short way on both sides and then runs flat, for a tray or coffer ceiling.

SBCA’s list also includes bowstring, barrel vault, clerestory, cantilevered and tri-bearing trusses, among others. All diagrams on this page are schematic; the real web layout comes from the truss design.

How roof trusses are designed

Trusses are engineered products, and the 2024 International Residential Code, Section R802.10, treats them that way:

• Wood trusses must be designed in accordance with accepted engineering practice, and metal-plate-connected trusses designed and made to ANSI/TPI 1.
• A truss design drawing must show at least the slope or depth, span and spacing, the location of every joint, the required bearing widths and the design loads.
• The drawings go to the building official for approval before installation, are prepared by a registered design professional where the jurisdiction requires one, and arrive with the trusses.
• Trusses must be braced as the drawings require, or by accepted practice such as SBCA’s BCSI guide.

In practice the homeowner or builder supplies the roof shape, span, pitch, overhang and spacing, and the truss maker designs the rest. HomeGuide puts the material cost of a roof truss at $60 to $700 each, and replacing trusses at $5 to $14 per square foot installed.

Damaged trusses and repairs

The code is strict here. Section R802.10.4 says truss members must not be cut, notched, drilled, spliced or otherwise altered without the approval of a registered design professional, and loads such as HVAC equipment or a water heater cannot be added beyond the design load without verifying the truss can carry them. A truss cut to make room in the attic, or broken by a falling tree, needs a repair designed for it, usually a detail from the truss maker or an engineer. Do not cut webs out to gain storage space; an attic truss is the way to build that in. Our roof truss repair guide covers what to do first, who designs the repair, what it costs and truss uplift.

Sources

• Structural Building Components Association, Roof Trusses: what a roof truss is, its elements and the benefits SBCA claims for trusses.
• Structural Building Components Association, Truss Configurations: the two basic truss types, web patterns and truss shapes.
• 2024 International Residential Code, Chapter 8, Section R802.10: truss design, design drawings, bracing and alterations.
• HomeGuide roofing labor cost guide, dated November 7, 2025: truss material and replacement cost.
• All read on November 2, 2026. The diagrams are our own schematics. Every source is listed on the methodology page.

Related calculators and guides