Roof Truss Types: The Complete Guide
A roof truss is a pre-engineered, triangulated frame built from a top chord, bottom chord, and web members. There are three ways to classify one: by outer roof shape (gable, hip, gambrel), by interior ceiling profile (scissor, attic, cathedral), or by internal web pattern (King Post, Fink, Howe, Pratt). Pick a category below to open a free calculator for that exact truss type.
What Determines a Truss's Type?
Every roof truss shares the same three structural parts: a top chord (the sloped or level upper member that the roofing attaches to), a bottom chord (the lower, usually horizontal member, often doubling as the ceiling joist), and web members (the internal diagonal and vertical pieces that triangulate the frame and transfer load from the top chord down to the bearing walls). At every joint, a truss connects members with a gusset plate — a punched metal connector plate in wood trusses, or a bolted/welded plate in steel trusses.
What changes between truss types is the shape of that outer triangle (gable vs. hip vs. gambrel), the slope of the bottom chord (flat for a standard truss, sloped for a scissor truss, raised for an attic truss), or the pattern of the web members (King Post's single post, Fink's "W", Howe's compression diagonals, Pratt's tension diagonals). The table below summarizes each, with a link to its own free calculator.
By Roof Shape
By Ceiling Profile
By Internal Web Configuration
Specialty & Material
Truss Type Quick-Reference Table
| Truss Type | Typical Span | Best For |
|---|---|---|
| King Post | Up to 16-20 ft | Short spans, simple triangulation |
| Queen Post | 20-30 ft | Medium spans, open center bay |
| Fink (W-Truss) | 20-36 ft | Standard residential roofs |
| Howe | 30-50 ft | Heavier loads, timber diagonals |
| Pratt | 30-50 ft | Steel construction, wide spans |
| Fan | 36 ft+ | Long spans, agricultural/commercial |
| Scissor | 20-32 ft | Vaulted ceilings |
| Attic | 24-36 ft | Usable room-in-roof space |
| Gambrel | 12-24 ft | Barns, loft storage |
| Hip | 20-40 ft | High-wind regions |
| Flat / Parallel Chord | 16-40 ft | Low-slope roofs, floors |
Spans shown are common ranges for standard lumber grades and spacing. Actual maximum span depends on chord size, spacing, pitch, and load — always confirm with a stamped engineered truss design per TPI 1 and your local IRC/IBC requirements.
Frequently Asked Questions
What are the main types of roof trusses?
Roof trusses are grouped by roof shape (gable, hip, gambrel, mono, flat, butterfly), by ceiling profile (scissor, attic, cathedral), and by internal web configuration (king post, queen post, Fink, Howe, Pratt, Fan). Most residential roofs use a Fink web pattern inside a gable shape.
What is the most common roof truss type?
The Fink truss, with its distinctive "W" shaped web pattern, is the most widely used residential roof truss in North America because it gives an efficient strength-to-material ratio at typical house spans of 20-36 ft.
How do I choose the right truss type for my project?
Start with the roof shape you need (gable for cost-efficiency, hip for wind resistance, gambrel for loft space), then consider whether you need a vaulted ceiling (scissor or cathedral) or usable attic room (attic truss). A truss engineer finalizes the internal web pattern for your span and load.
Do all truss types use the same span formula?
The outer geometry (rafter length, height, roof area) follows the same span-and-pitch math across truss types. What differs is the internal web layout and member sizing, which depends on the specific truss type, span, spacing, and load — always confirmed by a stamped engineered design.