A joist hanger is a formed steel bracket that holds the end of a joist against the face of a beam, header or ledger, so the joist can sit flush with the top of the member it frames into instead of resting on top of it. The hanger carries the joist’s load into the supporting member through its nails or screws, which means the right size, the right coating and every specified fastener matter more than most people expect from a small piece of sheet metal.
This guide covers how joist hangers work, the main types, how to pick one, what to nail them with, corrosion rules for decks and treated lumber, and the installation mistakes inspectors flag most often.
How a Joist Hanger Carries Load
Without a hanger, a joist has to bear on top of a wall, beam or ledger. That works, but it raises the floor by the depth of the supporting member. A hanger lets the joist and beam share the same top line, which is why hangers are standard at flush beams, stair openings, headers and deck ledgers.
The load path is simple. The joist end sits in the hanger’s seat. The seat transfers that reaction to the hanger’s sides, and the face flanges pass it into the header through the face nails. Joist nails driven through the hanger sides into the joist hold the joist in place and add uplift resistance. If any link is weak (an undersized hanger, missing nails, wrong nails, a gap under the joist), the connection will not reach its published capacity.
Types of Joist Hangers
Face-mount hangers
The most common type. The flanges nail to the face of the header, either outward-facing (the usual version) or inward-facing (“concealed flange”) for joists near the end of a beam or ledger where there is no room for outside flanges. The American Wood Council’s deck guide specifically says to use hangers with inside flanges when edge clearances call for it.
Top-flange hangers
These hook over the top of the supporting member and are fastened to the top and face. They are used where the header cannot take many face nails, such as on engineered lumber, on a wood nailer bolted to a steel wide flange beam, or on masonry and steel with the appropriate fasteners or welds. Because the flange sits on top of the header, it can create a bump under the subfloor, so check the detail before ordering.
Skewed, sloped and adjustable hangers
Joists that meet a header at an angle in plan (skewed) or slope down to it (sloped, common with rafters) need hangers made or field-bent for that geometry. Never force a square hanger onto an angled joist. Adjustable models exist, but each has its own published capacity at each angle.
Hangers for I-joists, LVL and doubled members
An engineered I-joist is narrower in the web than at the flanges, and an LVL or doubled 2x is wider than a single 2x. Hangers are sized to the actual width and depth of the member, so a “2×10 hanger” will not fit a 9-1/2 inch I-joist or a doubled 2×10. Our wood I-beam sizes page lists common I-joist depths and flange widths if you need to match a hanger to a joist.
How to Choose the Right Hanger
Every hanger model has a load table from its manufacturer that lists the joist size it fits, the required fasteners and the allowable loads. Work through four questions:
- What is the joist’s actual size? Width and depth, including whether it is single, doubled, an I-joist or an LVL.
- How deep is the header? The hanger must fit within it. The AWC deck guide requires deck joist hangers to be at least 60% of the ledger or beam depth.
- What load does the joist deliver? On a house floor this comes from the plans or the engineer. On a deck built to the AWC guide, it sets a minimum (table below).
- What is the exposure? Indoors in dry framing, outdoors, against preservative-treated lumber, or near salt water. This decides the coating.
For decks, the American Wood Council’s Prescriptive Residential Wood Deck Construction Guide (DCA 6-15) sets a minimum vertical capacity for each hanger (checked October 2026):
| Deck joist size | Minimum hanger vertical capacity (lb) |
|---|---|
| 2×6 | 400 |
| 2×8 | 500 |
| 2×10 | 600 |
| 2×12 | 700 |
The DCA 6 commentary explains that these figures come from the worst-case joist reaction for each size: Southern Pine joists at 24 inches on center at their maximum allowed span. Any hanger you pick must meet or beat that number in the manufacturer’s load table, with the fasteners the table calls for.
Outside a prescriptive deck, there is no shortcut. A hanger at a flush beam supporting a floor, a girder truss or a roof load must be selected from the manufacturer’s table against the reaction the designer calculated. Hangers carrying anything beyond ordinary joists, such as a flitch beam or a beam framing into another beam, should be specified by a licensed structural engineer.
Joist Hanger Nails and Screws
The published capacity of a hanger assumes the exact fastener in its table, in every hole marked for it. Common substitutions that void the rating:
- Drywall or deck screws. They are hardened and brittle, and they are not rated for the shear a hanger puts on them. Use only the structural connector screws a manufacturer lists for that hanger.
- Roofing nails or short nails. Use the nail diameter and length in the table. Short “joist hanger nails” are meant for specific holes, usually the joist nails, and some tables reduce capacity when they are used in the face holes.
- Skipping holes. Fill every hole the table requires. Some hangers have optional holes for higher loads; those count only if you fill them.
- Mismatched coatings. An electro-galvanized nail in a hot-dip galvanized hanger on treated lumber will corrode first.
One useful detail from the DCA 6 commentary: research showed hanger-to-ledger connections also resist lateral loads, and where the hanger manufacturer permits it, screws instead of nails at the ledger can reduce the chance of the joist pulling away from the ledger.
Corrosion: Decks and Treated Lumber
Modern copper-based wood preservatives are more corrosive to steel than old-style framing lumber, so outdoor hangers need heavier zinc or stainless steel. DCA 6 requires connectors such as joist hangers to be galvanized or stainless. Hardware galvanized before fabrication must meet ASTM A653 G-185, hardware galvanized after fabrication must meet ASTM A123, fasteners and connectors must be the same corrosion-resistant material, and anything within 300 feet of a salt water shoreline must be stainless steel grade 304 or 316.
Simpson Strong-Tie’s corrosion guidance (checked October 2026) adds two practical points: not all preservatives are equally aggressive (it notes ACQ-Type D is more corrosive than copper azole, micronized copper azole or CCA-C), and fasteners and connectors should have similar electrochemical properties to avoid galvanic corrosion. Ask the lumber supplier for the treatment chemical and retention level, then pick the finish the hanger maker recommends for it.
For background on why zinc coating thickness matters, see does galvanized steel rust, and for the trade-off between the two outdoor options, galvanized vs stainless steel.
Installing a Joist Hanger Step by Step
- Mark the joist layout on the header so each hanger lands on its line.
- Set the height. Hold a short offcut of the joist material flush with the top of the header and slide the hanger up around it. This keeps the joist flush and the seat tight to the bottom.
- Fasten one face flange, then the other, keeping the hanger square to the header.
- Cut the joist to length so the end gap at the header is small. A large gap leaves the joist bearing only on the seat edge and puts the joist nails in poor positions. Check the manufacturer’s limit.
- Seat the joist fully on the bottom of the hanger. Do not shim under the joist inside the hanger.
- Drive the joist nails at the angle the hanger’s dimples guide, into every required hole.
Common Mistakes Inspectors Flag
- Hanger too shallow for the joist, or a 2×8 hanger on a 2×10.
- Missing nails, wrong nails or screws not listed by the manufacturer.
- Joist not bearing on the seat (a gap under the joist).
- Hanger bent open to accept an oversize member, or bent to fake a skew.
- Indoor-grade coating on a deck or against treated wood.
- Clip angles or L-brackets used in place of a hanger. DCA 6 says not to use them to support joists.
- On decks, joists hung from both sides of the same beam. DCA 6 does not allow it, because its beam and footing tables assume joists frame in from one side only.
If you are confused about which member is the joist and which is the header in your framing, our explainer on girder vs beam vs joist sorts out the terms.
Joist Hangers FAQ
Can I use screws in joist hangers?
Only structural connector screws that the hanger’s manufacturer lists for that model, in the holes and quantities shown in its table. Deck screws and drywall screws are not acceptable substitutes.
Do I need joist hangers on a deck?
Joists attached to the side of a ledger or a flush beam need hangers. Joists that bear on top of a drop beam do not need them, but DCA 6 still requires each joist to be attached to the beam, and joists that overhang the beam need blocking between them at the bearing.
What gauge are joist hangers?
It varies by model and load rating, from light gauges for small joists to heavier gauges for beams and girders. The gauge is listed on the manufacturer’s product page. Our steel gauge thickness chart converts a gauge number to inches.
Can joists frame into both sides of a beam with hangers?
In engineered floor framing, often yes, if the beam is designed for the load from both sides. On a deck built to DCA 6, no. The guide prohibits it. Either way, a licensed structural engineer should size the beam and its connections.
Can I reuse old joist hangers?
It is not a good idea. Old hangers may be bent, corroded or have enlarged nail holes, and their rating assumed new fasteners in sound holes. New hangers are cheap compared with the risk.
Reference information only, not engineering advice. Disclaimer.