Framing connectors - Joist Hangers, Brackets, Connectors: this article explains the proper selection and installation of structural connectors, brackets & tie plates used to connect deck or porch framing and support members.
USP connectors such as joist hangers, joist angles, joist supports, stud shoes, skew hangers, and face mount hangers used for connecting these hangers and connectors are described, their uses explained, and their applications and specifications linked.
Both galvanized steel and stainless steel joist hangers, connectors, & brackets may be applied.
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How to Choose the Correct Joist, Beam & Post Connectors, Brackets, Joist Hangers & Other Structural Connectors for Decks & Porches
A Photo Guide to Metal Joist Hangers, Bolts, & other Connectors Used in Deck, Porch & other Building Framing Construction
Our page top photo shows a hybrid deck structure that encompasses a boat.
No fasteners were found securing the boat to the deck however.
At minimum, all structural hardware for decks should be hot-dipped galvanized steel. For the best protection, use stainless steel (see “Joist Hangers and Connectors,” below). At connections carrying structural loads, such as deck ledgers or railing posts, use through-bolts or lag screws.
How to Make Secure Post to Beam or Girder Connections for Decks & Porches
As described in Best Practices Guide to Residential Construction, Chapter Four, Best Construction Guide for Building Decks and Porches:
For the strongest connection of beam to post, place the
support beam directly on top of the posts (photo at left), rather than bolting them to the side, so the full load is transferred to the
For a more streamlined appearance, joist hangers are acceptable. Make sure the hangers and nails are approved by the manufacturer for use with the new types of pressure- treated wood (ACQ or ACZA) and fill all the holes in the hangers with properly sized nails. In general, nail into the joists with 1 1/2-inch joist-hanger nails and nail into the beam with 10d to 16d common nails, as specified by the hanger manufacturer.
Notching a 6x6 Post to Support & Connect to a Deck Beam
A double 2x beam can rest on a notched 6x6 post, as shown. For the strongest connection of joists to the support beam, the joists should sit on top of the beam
In our photo the 6x6 post was notched to leave a thick component that could be through-bolted (or lag bolted) to the girder. You'll also see toe-nails up through the post top into the girder bottom, and additional common framing nails securing the post to the beam.
Don't cut the notch out of the center of the 6x6 post for a double 3x beam - the remaining lumber on the post top will be too thin and risks splitting and failure.
Using a scab to tie deck posts to girders
But in our photo the installer put the scab on just one side of the post, and used just 10d common nails for fasteners.
To be secure, the scab should be bolted to the girder and through the post as well. Through-bolts (illustrated below) are stronger and should be used where possible.
For the heaviest connections on a deck, such as where ledgers attach to the house or to posts, use 1/2-inch bolts or lags.
A look at the other side of the deck girder (beam) above shows that the builder must have been short on nails. We don't see nails securing the two 2x10's together - at least none on this side (a weaker construction method), and we see no fasteners making any attempt to tie the girder to the post top.
Everything relies on that 2x6 scab that was ticky-tacked to one face of the post and beam. We recommended the addition of through bolts.
When drilling holes through a scab or other framing member, and if multiple bolts are to be installed (red circles on the scab in the photo at above left), I [DJF] like to stagger the bolt hole positions in order to assure that no two bolts run through the same vertical grain in the wood.
That's the strongest connection as it reduces the chances of splitting of the wood between two holes drilled in the same grain section of the lumber.
You'll also notice that we don't place the bolts too close to the end of the scab nor too close to the top or bottom edge of the girder nor too close to the top of the post - locations where splitting may be more likely.
The two 2x10's comprising the deck girder in our photo above have not been bolted together.
That may be OK if the girder was toe-nailed from opposing sides. Some builders who want a stiffer girder add structural adhesive and even a treated plywood plate between the 2x lumber to build the girder. Especially where a plywood stiffener is installed, be sure to provide flashing over the top of the girder to protect the structure from water and frost damage.
Place large washers under the heads of lags and at both ends of through-bolts. Re tighten bolts and lags after the first year and check periodically for tightness.
Joist Hangers and Steel Connectors Used for Wood Framing & Deck Construction
Stainless steel offers the best protection. Type 304 or higher stainless steel is recommended for very wet environments such as poolside decks; or Type 326 for exposure to salt or saltwater.
Watch out: Also, do not mix metals: Use stainless-steel fasteners with stainless-steel connectors and galvanized fasteners with galvanized connectors.
And at FRAMING FASTENERS, NAILS, SCREWS, & HIDDEN we include examples of fasteners that should not be used in joist hangers, such as drywall screws and other non-structural screws. or roofing nails.
Also see New Preservatives and Corrosion where we describe structural fasteners designed for use in pressure-treated lumber.
Our photo (above left) shows a typical steel joist hanger used to speed and aid the construction of a deck. Notice that the height of the steel hanger is matched to the depth of the joist.
Continuing from from Best Practices Guide to Residential Construction:
Like other deck components, metal fasteners are subject to numerous stresses. The sealers and stains typically used
on decks provide little protection to fasteners, and the copper-based chemicals used in most waterborne preservatives
accelerate corrosion in many metals.
Also notice that the proper galvanized steel joist hanger nails were used, not roofing nails or other fasteners. If you select the proper depth of joist hanger to match the depth of the deck joists, the manufacturer is giving you a clue about the number of nails required to make a safe and secure connection - every hole in the hanger gets a nail.
Watch out: choose the right joist hanger for the size of joist being supported. Don't use a joist hanger intended for 3x4's to hang a 2x6 or larger framing member - the number of nails won't be sufficient.
If you encounter a structure already built with this mistake, fixing the connections is usually easy: add the required number of additional fasteners by toe-nailing the joist or rafter from opposing sides, using an appropriately sized framing nail or galvanized framing nail if outdoors. (Typically 12d common galvanized).
How Many Nails or Screws do I Need to Connect Two Framing Members?
The architect or engineer who designs a building specifies the number and type of framing connectors to be used for each type of connection. But there are also good sources of connector information from the manufacturers of framing connectors (right in the catalog or in installation sheets), as well as in various engineering and carpentry texts.
A still more basic clue is the number of holes in the framing connector itself.
Watch out: the number of holes in a typical joist hanger is a clue to the number of nails that the manufacturer expected you to use to make a secure connection. Our pocket-knife is pointing to missing framing nails in the 2x4-sized framing-connector above. There were no nails into the butting framing member.
Toe Nailing Wood Framing Connections
Toe-Nails Instead of Joist Hangers are OK for Framing Lumber Butt-Joint Connections, but Don't Over-Nail
It is not necessary to use steel joist hangers if the joist is properly toe-nailed from either side into the ledger board, provided that the proper size and number of nails are used.
Our illustration (left, adapted from a Double-Shear stamping on a steel joist hanger) explains why toe-nailed lumber connections can be very strong.
Use of toe-nailing, or angled opposed framing nails (Double-Shear in Simpson Strong-Tie's patented joist hanger such as the item adapted above), can permit the use of fewer total nails in a wood frame construction.
Detals about how to use toe-nailing in wood frame construction are
Installation Details for Steel Framing Connectors for I-Joists
As we illustrate its installation here, the connector is nailed over the side of the I-Joist, then to the wall top plate, then to the wall stud below, forming a very strong connector where these I-Joists were used as roof supports.
Our first photograph (left) shows ;that we installed the specified number of joist-hanger nails (minimum of five) through the connector end and into the top of the I-Joist.
Our two photos below illustrate the required position and number of nails for the extended connector strap as it passes over the wall top plate and along the side of the I-Joist where it was nailed to the top chord tie and to the block inserted at the end of the I-Joist (below left) and then over the top plate (4 nails) and finally along a wall stud inner face (3 more nails) giving us 7 fasteners in the I-Joist itself.
An additional 4 nails into the top plate and at least 3 (depending on how the strap aligns) into the wall stud) give us 7 fasteners into the structural wall below. If additional nails are needed into the wall stud the strap can be bent around the stud side for that purchase point.
This I-joist installation was for framing a low-slope roof in new construction.
The layout required some planning and thought to assure that the I-joists were placed over wall studs in a location to permit the strapping of I-Joist to both the wall top plate and the wall stud using a single strap.
If your plans don't work out quite so precisely you will still be OK but if your I-Joist connector straps don't line up to tie all three wall components together at once, you may be required to install additional ties to connect certain wall studs to the building top plate.
At left we illustrate installation of the same utility framing connector strap at the opposite side of the same building as the structure above. In this location the lower ends of the framing connectors were nailed from the exterior of the building, through the OSB structural sheathing and into wall studs below.
[In my [DJF] OPINION, nailing the strapping to OSB alone, that is, not also through it into the wall studs, is not so strong.] Photos courtesy of Daniel Friedman & Galow Homes.
I-Joist Hangers for Flat or Angled Framing Between Walls Rather than On Top of Walls
Above we illustrated using steel framing connectors to tie I-Joists to a wall top plate and stud for the case of I-joists that run on top of the building walls. Simpson Strong Tie and other manufacturers provide straight (for floors) or angled I-Joist hangers for framing I-Joists between building walls such as for installation of a floor, a flat roof, or a roof with no overhang.
Machine-Threaded Bolts Used for Deck Construction
Drill pilot holes 1/32 to 1/16 inch larger than the diameter of the bolt so it will slide through easily.
After drilling, saturate the hole with preservative. Use large washers under both the head and nut. Re tighten after the first year, since the wood may have shrunk.
Photo at left courtesy of Mark Morsching., EverFlashing.
Lag Bolts Used for Deck Construction
So, for example, a 1/2-inch lag would get a 5/16-inch pilot hole for the threaded portion; a 3/8-inch diameter lag would get a 1/4-inch diameter pilot hole.
After drilling, saturate the pilot hole with wood preservative. It is also important that at least half the length of the lag is threaded into solid wood.
For example, driving a 5-inch lag through a 4x4 post into a 2x joist will produce a weak connection with only 1 1/2 inches of anchoring. Instead, the lag screw should go through the 2x and be threaded into the thicker 4x4.
Use a large washer under the head, and re tighten after the first year in case materials have shrunk. Our photo (above left) illustrates use of a lag bolt to connect the deck ledger to the building structure by bolting to the rim joist. Notice that the installer seems to have omitted flashing over the ledger board.
Suppliers of Joist, Post & Beam Hangers & Connectors & the Nails or Fasteners used With Them
Stainless steel or galvanized steel joist hangers, connectors and similar products are produced by Simpson Strong Tie, Incom, Schuler Manufacturing, State Metals, Daytona Bolt & Nut, Hutchinson, Cleveland Steel, Tamlyn, U.S. Lumber, Hohmann & Barnard, and Direct Tools & Fasteners as well as Paslode, Grip Rite joist hanger nails and other specialty nails.
-- Adapted with permission from Best Practices Guide to Residential Construction.
This article series discuss best porch & deck construction practices, including choice of framing materials, decking or flooring choices & installation, how to select and use deck and porch structural and flooring fasteners, actual deck & porch framing construction details & connections, deck joist & beam span tables, how to build leak-proof rooftop decks, construction of covered & screened porches, deck & porch railing construction & materials, choices of finishes and stains for decks & porches, and past & current deck lumber preservative treatments with related health & environmental concerns.
Continue reading at FRAMING FASTENERS, NAILS, SCREWS or select a topic from the More Reading links shown below.
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