A joist is any horizontal framing member that supports a floor or flat roof. The term joist hanger refers to metal brackets that support joist beams and connect the beams to walls and foundations. Joist hangers vary according to the size of the joist beam that they carry, the composition of the hanger's metal, hanger design features and aesthetic features.
Joist Hanger Sizes
The defining characteristic of a joist hanger is its size. Joist hanger manufacturers engineer and manufacture joist hangers to hold specific pieces of dimensional lumber, such as 2x4 lumber and 2x6 lumber. Architects, builders and building materials retailers typically refer to a joist hanger by its size. For example, the term "2x4 joist hanger" refers to a to a hanger that holds 2x4 lumber. Although hardware stores usually stock only common sizes, large sizes and special dimensions may be ordered.
Hanger Metal Type
To safely support structural framing members, such as joists, joist hangers must resist corrosion. The most common types of corrosion-resistant joist hangers are zinc-plated, hot-dipped and stainless steel. A zinc-plated hanger undergoes an electrochemical process that bonds a layer of corrosion-resistant zinc atop its steel frame. Hot-dipped hangers also receive a zinc coating but are dipped into a molten vat rather than electroplated. Stainless steel hangers receive no coatings; the mixture of metals used to produce stainless steel naturally resists decay.
The term flange refers to the hole-studded "ears" that stick out from a hanger's sides. Flanges rest flat against walls and foundations, allowing builders to drive nails through the flange holes and attach the hanger to the surface. Speciality flanges do not protrude from a hanger's sides like ears; some speciality flanges sit concealed behind the joist while others jut from the hanger's top.
Joist Hanger Slope
The seat or "saddle" of a joist hanger rests between the hanger's ears. A joist rests directly within the hanger's three-sided seat. Although most joist hangers hold horizontal joists, the "saddle" or seat, of some joist hangers slopes to hold angled joists and rafters. Builders often use sloped joist hangers to attach patio cover rafters to existing walls.
Aesthetics and Appearance
Major joist hanger manufacturers offer several styles of joist hangers for exposed applications. Projects that often require exposed hangers include post and beam construction, log home construction and rustic-themed interiors. Decorative hangers are often painted and feature decorative cuts along their sides.