Guide to Types of Deck & Porch Metal Fastener Coatings & Materials

Our photo (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.

When the fasteners corrode, they contribute to decay in the surrounding wood, further weakening the connection.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.

Toe-Nails Instead of Joist Hangers are OK 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.

Using too few toe-nails in framing lumber is going to make a weak structure that could collapse. But using too many nails in framing lumber will also cause a weak connection that can lead to deck collapse because an excessive number of nails actually fractures the lumber.

Our photo (left) shows about 30 nails shot by the builder during framing of this home. The framer was trying to drive a recalcitrant stud into position. Clamps might have worked better. This stud was so split as to lose its structural integrity, and replacement of this wall stud was needed.

Because the “toe-nails” cross one another in the header or ledger board when used to secure a deck joist, this connection can actuallty be stronger than end-nailing the deck joists from the other side of the ledger or girder.

Because the new wood preservatives ACQ (alkaline copper quat) and copper azole contain significantly more copper than the older CCA-treated lumber, they are estimated to be two to four times more corrosive to metals and galvanized coatings than the CCA they are replacing.

• Hot dipped galvanized nails: At bottom is a 1.5″ long hot-dipped galvanized nail made by Simpson, and discussed just below. This is the proper fastener to use with galvanized steel joist hangers.
• Drywall screws: In the middle is a 1.5″ drywall screw. These screws are tempting to use because they are available, easy to install, do not require drilling. We have inspected decks constructed entirely using interior drywall screws for both decking and for structural connections and joist hangers. Do not do this. This is an improper fastener that will fail and risks catastrophic deck collapse.
• Stainless steel utility screws: At the top is a 1 1/4″ stainless steel screw used by a contractor to secure joist hangers when building the deck shown at the top of DECK & PORCH CONSTRUCTION. Although this screw is also made by a company that makes structural fasteners, a quick look at the company’s specifications for this screw revealed that the manufacturer specifically advised that this screw was not a structural fastener and should not be used with steel framing connectors.

  The contractor removed the screws and used the proper fasteners instead. Stainless steel, galvanized, as well as proprietary-coating surfaced construction screws for use with treated lumber are available and of course are fine if used as recommended. But not the two screws shown in this photo and removed from decks we inspected.