Like most DIYers, I’ve occasionally used joist hangers, post bases and fence brackets, along with assorted lumber connectors I have no name for. Choosing and installing them often has come down to guesswork: Is this the right size and gauge? What’s that prong for? Why is that hole a triangle and the other a circle? If I bend the tab back, will this thing fit?
Rather than continuing to play guessing games, I decided to learn more about lumber connectors. While visiting the headquarters of USP Structural Connectors in Montgomery, Minnesota, I had an informative discussion with representatives Kristi Peterson, Tim Comstock and Barry Ashwell. It soon became clear that much of what weekend builders “know” about these seemingly simple pieces of hard¬ware is wrong — in some cases, dangerously so.
Fabricated joist hangers began to find favor among builders in the 1950s. Although the number of spe¬cialty products has increased expo¬nentially since, joist hangers, post bases and post caps still account for most of the usage — particularly among DIYers. Today USP and California-based Simpson Strong-Tie Co. dominate the national market. Both companies list more than 4,000 product options in their virtually identical catalogs.
Metal lumber connectors are stamped, folded or die-cut from sheet steel. The most popular DIY products are fabricated from 14-gauge (5/64-ii), 16-gauge (1/16-in.) or 18-gauge (3/64-in.) steel. The cheapest products are made of galvanized sheet steel with about 0.6 ounces of zinc per square foot of surface area. (Zinc is the principal ingredient that protects metal from rust and corrosion). Corrosion-resistant galvanized steel with about 1.8 ounces of zinc per square foot is used to make connectors for exterior exposure. (USP dubs this product line Triple Zinc; Simpson calls its version Z-Max.)
Less common (and costlier) are stainless steel connectors and hot-dipped galvanized connectors, which are treated with galvanizing solution after fabrication. Both typically are special-order items.
Availability of metal connectors varies widely by region, but local retailers will have full-line catalogs so you can special-order just about anything you need. You can also obtain information from manufac¬turers (see SOURCES).
Joist hangers (and comparable hard¬ware) support joists, rafters or purlins. The hangers typically are mounted so the tops of the joists are level with the tops of the sup¬porting beam. Face-mount joist hang¬ers that attach to the face of the beam or ledger are the most familiar. Top-mount hangers have tabs or straps that fit over the top of the beam, pro¬viding more load support than comparable-size face-mount hangers. The downside is that the top-mount portion of the hanger is thick enough to create problems when installing a subfloor or decking.
Joist hangers are sized to accom¬modate standard dimensional lumber widths and thicknesses. Double-joist hangers and triple-joist hangers are available in some styles, as are hang¬ers sized to accept 4x stock and common engineered-beam dimen¬sions. The hanger can be shorter than the width of the lumber, as long as the top of the joist hanger covers at least 60 percent of the width, measuring up from the bottom. Translation: It’s okay to use a 2x6 joist hanger with a 2x8 joist.
The ongoing shift away from CCA ¬treated lumber to nonarsenic preserva¬tives has produced one largely unforeseen problem: corro¬sion. Field experience and industry testing indicate that new wood-preserving chemicals (ACQ and copper azole) can accelerate metal corrosion much more than CCA, potentially leading to premature failure of metal fasteners and connectors. According to most industry experts, a relatively inexpensive defense against corrosion and rusting it to use high-zinc galvanized connectors (such as USP’s Triple-Zinc products or Simpson Strong-Ties Z-Max line) and hot-dipped galvanized fasteners for exterior projects. A more certain (and costlier) way to fend off corrosion is to use only stainless steel connectors and fasteners. — MJ
Post bases and caps
A post base is anchored to a con¬crete footing and nailed to the bot¬tom of a wood post to hold it in position. In most cases, the post base is bolted to a J-bolt set in con¬crete, but some have integral straps you embed directly into wet concrete. Post bases usually have a metal standoff plate to raise the post bot¬tom, minimizing ground contact that can lead to rot. Most J-bolt-secured bases have a slot or an enlarged bolt-guide hole so the post can be adjust¬ed slightly for alignment.
Metal bases do not provide enough side-to-side rigidity to support posts that are unsecured at the top. Fence posts and other posts that are not connected to a secure beam must be set directly into the ground or concrete. Most hard¬ware retailers carry post bases sized to hold standard 4x4 and 6x6 posts. Bases for 8x8 posts can be ordered.
The most common post bases should be attached to posts with 16d hot-dipped galvanized nails. Some post bases feature opposing guide holes for bolts to increase uplift resistance.
Posts caps (sometimes called post saddles) are attached to post tops to provide a strong joint with over¬head beams and joists. One-piece caps are sized for use with beams of many thicknesses, but most retailers carry only those intended for use with 4x or 6x beams. Two-piece caps can be adjusted within a limited range to sandwich beams of nonstandard thick¬ness, including doubled 2x lumber that would require a 1/2-in. spacer for use with a one-piece 4x4 cap.
Post caps are used to join post tops with beams. Two-piece caps for end posts (A) and mid-run posts (B) can be adjusted slightly. One-piece caps (C) sized for 4x or 6x members are inexpensive and easy to install.
In most cases, post caps should be attached with 16d nails. For greater uplift protection in areas subject to high winds, hurricanes or seismic activity, use joist-hanger screws to attach post caps.
Other useful connectors
Joist hangers and post hardware repre¬sent only a fraction of the metal connec¬tor products you can buy. You’ll find whole lines of connectors for working with trusses and with engineered wood products, such as glulam or I-joists. There are straps and hangers and hold-downs for masonry walls, steel beams, metal posts and more. In fact, connector catalogs contain an absolutely dizzying array of straps, ties, clips, plates, angle brackets and stair brack¬ets. Most have a specific purpose, but they are also handy for repairs and for making shop furnishings.
The right fasteners
Using the wrong type of fastener is probably the most common error DIYers make when installing lumber connectors. To avoid mistakes, consult the detailed nailing sched¬ules in the manufacturer’s catalog before installation.
With few exceptions, connectors should be installed with nails. Joist-hanger nails (10d x 1-1/2-in. hot dipped galvanized) are typical for face-nailing connectors to 2x lumber. For attaching connectors to thicker lumber, such as posts, 10d or 16d nails are typi¬cal. The fasteners must be rated for your application. If the connector will undergo exposure, choose hot-dipped galvanized fasteners (unless you are installing stainless steel hardware, which requires stainless steel fasteners).
Never use roofing nails or drywall screws to install joist hangers or post hardware. The temptation to use deck screws can be great (especially if you’re fastening a framing member that tends to move out of position or bounce from the impact of hammer blows), but you should resist it in most cases. One exception I’ve found involves hanging metal fence brackets that suspend flimsy wood fence panels between posts. For this light-duty job, ordinary deck screws are suitable fas¬teners. But be careful not to overdrive the screws because the metal hanger can cause the screwhead to snap off under pressure.
Both Simpson and USP make 1/4-in.-dia. screws designed for use with lumber connectors. The hex-head screws actually have greater shear resistance than 10d joist-hanger nails as well as uplift resistance comparable to bolts (depending on screw length). The screws, which are specified for some connectors, are considerably more expensive than joist-hanger nails.
Some codes allow air-driven nails to be used with lumber connec¬tors, but check with your local build¬ing department. Codes often require full-head pneumatic nails and do not allow the clipped-head nails found in most coils. Several pneumatic fasten¬er manufacturers have introduced full-head nails in coils recently; ask your building materials supplier for more information.
CAUTION: Do not attach metal connectors with pneumatic nails unless the nail gun has a special self-registering trip for use with metal connectors or the connector is specifically designed for use with nail guns.
To meet the stated load ratings, metal connectors must be installed with fasteners that are long enough to penetrate the lumber by a distance equal to 12 times the diameter of the nail. Bolts must be driven through guide holes 1/32 to 1/16 in. larger than the diameter of the bolt. Use compatible washers wherever the bolt or nut seats against a material other than the connector.
You might not expect wooden fence rails and chain-link fence posts to be compatible. That’s why I dreaded removing my old chain link fence posts to make way for a new wood fence. But then I discovered Simpson Strong-Tie’s Pipe Grip Ties ($1.50 each), which are designed to connect wood fence rails to round metal posts. (USP also makes a product to connect metal posts to wood rails). The fasteners are sized to fit standard 1-1/2- or 2-in.-dia. pipe posts. They are secured to the posts with a bolt or set-screws and then fastened to the fence rails with 1/4 x 1-1/2-in. wood screws. You can paint the fence and the posts, but I chose to leave the cedar untreated so it will fade to gray and eventually blend with the posts.
For more information, go to www.handymanclub.com
Simpson Strong-Tie Co.
USP Structural Connectors 800-328-5934