Simpson Strong-Tie Post Caps: BC, AC, and PCZ Series Explained

Post caps are one of those connectors that show up on nearly every outdoor build. Any time a beam is sitting on top of a post, you're going to want a post cap to keep the connection from uplift and lateral movement. Decks, pergolas, carports, fences, patio covers, and exterior columns all use them. 

Simpson Strong-Tie makes several distinct series that cover everything from light-duty deck framing to heavy structural columns, and picking the right one isn't complicated once you understand the differences between them. This guide breaks down the BC, AC, PC/PCZ, and LPC series, with the models, dimensions, load information, and finish options for each.

A post cap is a metal connector that wraps around the top of a post and attaches to the beam sitting on top of it. The two flanges on the inside grip the post, and the flanges on the outside face nail into the beam. This mechanical connection does two things that a simple resting connection can't do. First, it resists uplift, which is the vertical force that tries to pull the beam up off the post when wind loads act on the structure. Second, it resists lateral movement, which keeps the beam from sliding sideways on the post under horizontal loads.

Without post caps, the connection between a post and beam is just gravity. That works fine under normal dead loads, but it fails quickly when the wind hits a pergola from the side or when seismic activity shakes a carport structure. For any structure that's attached to a house or that needs to meet building code, post caps aren't optional. Even on freestanding backyard structures, a properly capped post-to-beam connection is what separates a structure that stays put in a storm from one that doesn't.

Simpson Strong-Tie post caps are listed under ICC-ES Evaluation Reports ESR-3096 and ESR-2604, which cover code compliance under the IBC and IRC. If your build needs an inspection, these reports give the inspector the documentation they need.

Simpson offers four main types of post caps, each designed for a different type of wood-to-wood connection. The BC series is a simple one-piece cap commonly used on decks, pergolas, and other outdoor structures. The AC series features a two-piece adjustable design, making it a good option for retrofit projects or situations where the post and beam aren't perfectly aligned.

For larger posts and heavier loads, the PC and PCZ series provide a stronger one-piece connection. The LPC series is a lighter-duty adjustable cap that's a good fit when you need a low-profile connector for smaller projects.

Each series is available in multiple sizes and finishes, with fastening requirements that vary by model. Choosing the right post cap comes down to the size of the members you're connecting, the load requirements, and whether adjustability is important for the installation.

The BC is Simpson's most commonly used post cap for residential outdoor construction. It's a one-piece 18-gauge cap with flanges that wrap both the post and the beam. The opposing flanges on the post side increase lateral resistance, which is important on structures that see horizontal loading from wind or bracing forces. The BC attaches with 0.162" x 3-1/2" common nails or pneumatic nails and reaches full allowable load with either type, which keeps things flexible on the jobsite.

Size options cover 4x, 6x, and 8x nominal posts, plus the BC46 for a 4-inch beam bearing on a 6-inch post, which is a common configuration in pergola and patio cover framing. All BC models are also available in a rough lumber variant (designated with an "R") for areas where dimensional lumber isn't used. The BC4 is the go-to for most residential deck post-to-beam connections. The BC6 and BC6Z are the standard choice for 6x6 pergola posts and patio cover columns.

Finish options for the BC are G90 galvanized, ZMAX, and stainless steel. G90 is the base option for most residential applications in dry or moderate climates. ZMAX is the right choice when the cap will touch pressure-treated lumber. Stainless is available for BC4, BC6, and their rough lumber counterparts, for use in coastal environments or anywhere long-term corrosion resistance is critical.

The AC is a two-piece adjustable post cap that wraps the post on two separate flanges rather than being a single stamped piece. This two-piece design is useful in a few specific situations. It eliminates nailing into the end grain of the post, which is weaker than face nailing. It's also easier to install in retrofit applications where the beam is already sitting on the post and you need to slide the cap in from the side rather than drop it over the top. The AC4 and AC6 are both 18 gauge and come in G90, ZMAX, and stainless steel.

One important note on the AC: the load table lists values for a pair of caps, not one. You need two AC caps per connection, one on each face of the post. If you install only one side, multiply the table loads by 0.4. For a full double-sided installation, the AC6 at maximum nailing (round and triangular holes filled) reaches 2,920 lbs uplift and 2,125 lbs lateral with Strong-Drive SD Connector screws. That's a meaningful load rating for an 18-gauge connector, and it makes the AC a legitimate structural cap rather than just a light-duty strap.

The nailing pattern has two options: minimum and maximum. Fill only the round holes for the minimum load and fastener count. Fill both the round holes and the triangular holes for the maximum. The triangular holes are clearly different in shape so there's no confusion in the field. Use the minimum if the design demand doesn't require full load, but if you're unsure, filling all holes is never wrong.

Note: Loads listed are for two-cap installations (one per face). For single-sided installations, multiply table loads by 0.4 per engineering letter L-C-ONEPOSTCAP26. 

Code compliance: ESR-3096, ESR-2604.

When the BC's 18 gauge isn't enough, the PC and PCZ series step up to 16 gauge. These are heavier one-piece caps designed for larger posts and higher load demands. The PCZ designation means the cap comes standard in ZMAX finish, which makes these caps ready for contact with pressure-treated lumber right out of the box without needing to specify a different finish variant.

The PC6Z and PC8Z are the inline versions, designed for posts where the beam runs continuously over the top. The EPC series handles the end-of-beam condition, where there's framing on only one side of the post. If you're building a pergola and the outermost post has only one beam framing into it, the EPC is the correct connector, not the inline PC. Using an inline cap on an end condition leaves one flange unsupported, which affects how the load transfers and could be flagged at inspection.

The LPC6Z is a lighter, adjustable option in this category. It's a two-piece design that adjusts to fit different post widths and is good for applications where a lighter connection is structurally sufficient and you want a lower-profile look. It's adjustable for nominal lumber (as opposed to the rough lumber sizing on the ACR and BC4R).

Note: Load values for the PC and PCZ series vary by post size and nailing pattern. Refer to the Simpson Strong-Tie Wood Construction Connectors Catalog (C-C-2026) or the Simpson Post-to-Beam Selector tool for specific load tables. 

Code compliance: ESR-3096, ESR-2604.

Every post cap series comes in multiple finish options, and picking the right one is as important as picking the right size. The wrong finish in the wrong environment is a corrosion problem waiting to show up after the build is done.

G90 is the standard finish for post caps used in protected, dry locations. It's the baseline galvanized coating and is suitable for most interior or above-grade outdoor applications in non-coastal regions. If you're building a covered deck in the midwest or an indoor post-and-beam connection, G90 is the standard call. It's the most economical option and meets code for standard residential work.

ZMAX is Simpson's thicker hot-dip galvanized coating. It's required any time the post cap will be in contact with pressure-treated lumber. Modern treated lumber uses copper-based preservatives (ACQ, CA, MCA) that accelerate corrosion on lighter galvanized coatings. ZMAX's thicker zinc coating resists that chemical environment. 

If your deck posts are treated or your pergola is going in a wet climate where treated lumber is specified at the base, use the Z-suffix model. On decks, ZMAX is the default choice since treated posts are extremely common.

Stainless is available on select BC models (BC4SS, BC6SS) and AC models (AC4SS, AC6SS). It's the right finish for coastal environments where salt air is a constant factor, for aquatic or pool-adjacent structures, and for any situation where long-term corrosion resistance matters more than upfront cost. 

Stainless costs more than zinc-coated options, but in a salt-air environment it outperforms galvanized finishes over the life of the structure by a significant margin. When you're building near the ocean or in a permanently wet environment, stainless is the call.

For standard residential deck construction with 4x4 or 4x6 posts, the BC4 or BC4Z is the most common cap you'll use. If you're building with 6x6 posts for a larger deck, step up to BC6Z. In most regions, deck lumber is pressure-treated, so the Z-suffix ZMAX finish is the correct version. The BC46Z handles the asymmetric configuration where a 4x beam bears on a 6x post, which shows up on decks with larger post sections for railing or aesthetic purposes.

Pergola and patio cover construction most commonly uses 6x6 posts with 2x or 4x beams. The BC6 or BC6Z handles most of these applications at the inline positions. At the end columns where there's beam framing on only one face, use the EPC series instead. 

If you're building a larger pavilion or covered structure with heavy timber or engineered lumber beams, check the load requirements and step up to the PC6Z or PC8Z as appropriate. For backyard builders who want a simple retrofit at an end post, the AC6Z installed on one side (with the load reduced by 0.4) may be the simplest option.

Carports and larger freestanding structures often use 6x6 or heavier posts and see more significant lateral and uplift loads than a basic pergola. For these applications, the BC alone may not be sufficient at the required load levels. Use the Post-to-Beam Selector on Simpson's website to enter your post and beam size, load demand, and installation type, and it'll filter to the right connector. The PCZ or CCQ series (heavy column caps with SDS screws) may be the right choice for heavier carport builds.

In coastal zones or any area with persistent salt air or high moisture, material selection matters as much as structural selection. Use the SS (stainless steel) variants of the BC or AC series. If stainless isn't available for the model you need, ZMAX is the minimum acceptable coating. Don't use plain G90 galvanized in a salt-air environment. The coating will degrade faster than expected and you'll be replacing connectors well before the structure's useful life is up.

The BC installs by setting the cap on the top of the post and nailing through the post flanges, then nailing through the beam flanges after the beam is placed. Fill every hole in the cap. Don't skip nail holes to save time. The load ratings are based on full nailing patterns, and a partially nailed cap performs significantly worse than the table values show. Use the right nail size: 0.162" x 3-1/2" for the BC. Using shorter nails or smaller shank diameters reduces the connection capacity.

For the AC, remember the two-cap requirement. Set one cap on each face of the post, making sure the cap seats squarely with no rocking or gap between the flange and the post face. For minimum nailing, fill all round holes. For maximum nailing, fill round and triangular holes. Don't mix minimum and maximum nailing on the two sides of the same connection.

When using BC caps on end-grain conditions (post tops), the load tables don't apply. End-grain nailing is significantly weaker than face nailing, and Simpson's evaluation reports don't list loads for that condition. The BC flanges nail into the post's face, not the end grain. If you're capping a glulam or LVL column where the cap nails into the narrow face (edge) of the member rather than the wide face, check Simpson's technical bulletin T-C-SCLCLM for the applicable reduction factors.

If you're building a deck, pergola, carport, or any outdoor structure with post-to-beam connections, post caps are needed. They're the reason your structure stays connected. The BC series covers the vast majority of residential outdoor applications in 4x, 6x, and 8x post sizes. The AC gives you flexibility for retrofit work and end-grain-free connections. The PC/PCZ series handles heavier structural demands. And for coastal or treated-lumber applications, you've got ZMAX and stainless steel options across the lineup.

Pick your series based on post size and load demand, match the finish to your environment and lumber treatment, and make sure to screw it down correctly.