How to Anchor a Deck Post to Concrete (Post Base vs Embedded)

Anchoring a deck post to concrete is one of the most important structural connections in a deck — it transfers all vertical and lateral loads from the deck frame to the foundation. A poorly anchored post can fail catastrophically under load. Here is exactly how to do it right.

Two Methods: Post Base vs Embedded Post

There are two ways to anchor a deck post to concrete — surface-mounted post bases and embedded (buried) posts. Each has different structural characteristics, code requirements, and installation difficulty.

Method	Best For	Pros	Cons
Surface-mounted post base	Existing concrete slabs, patios, piers	Post stays above grade, no rot; easier to replace post	Less lateral resistance; requires adequate concrete thickness
Embedded post in footing	New construction, high lateral loads	Maximum lateral resistance; proven method	Post contact with concrete accelerates rot; harder to replace

Method 1: Surface-Mounted Post Base (Recommended)

Surface-mounted post bases — like the Simpson Strong-Tie ABA or ABU series — anchor to an existing concrete surface using anchor bolts, then the post sits in the base above grade. This is the preferred method for most residential decks because:

• The post end stays above moisture and grade, dramatically extending post life
• Posts can be replaced without breaking up concrete
• Engineered load values are published in ICC-ES ESR reports
• Meets IRC requirements for post-to-footing connections

Step 1: Mark Post Locations

Establish post locations using batter boards and string lines. Use the 3-4-5 triangle method to ensure square corners. Mark the center of each post location on the concrete with a pencil or chalk.

Step 2: Install the Anchor Bolt

Most post bases use a 1/2" or 5/8" anchor bolt cast into fresh concrete or set into existing concrete with epoxy. For existing concrete slabs and piers:

• Drill to the required embedment depth with a 1/2" or 5/8" carbide masonry bit in a hammer drill or SDS rotary hammer
• Clean the hole thoroughly with compressed air
• For epoxy anchors: inject adhesive, insert threaded rod, allow full cure time before loading
• For wedge anchors: insert and torque to specification (25-35 ft-lbs for 1/2")

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Step 3: Set the Post Base

Thread the post base onto the anchor bolt with the washer and nut. Do not fully tighten yet — leave it slightly loose so you can make adjustments. Check that the base is plumb in both directions using a level before final tightening.

Step 4: Set and Fasten the Post

Drop the post into the base and fasten using the manufacturer-specified fasteners. Simpson Strong-Tie bases require 10d x 1.5" post base nails or specified structural screws — not standard construction screws. The number and type of fasteners determines the rated load capacity of the connection.

Brace the post plumb in both directions before attaching the beam above. Once the beam is connected, the bracing can be removed.

Method 2: Embedded Post in Concrete Footing

For new construction where you're pouring concrete footings, the post can be embedded directly into the wet concrete. This provides excellent lateral resistance but puts wood in contact with concrete — a long-term rot risk even with pressure-treated lumber.

Frost Depth Requirements

The footing must extend below the frost line for your region. Posts that don't go below frost depth will heave in winter, cracking the deck frame above. Use our Post Hole Calculator to find the correct depth for your city — frost depths range from 0" in southern US to 72"+ in northern Canada.

Footing Diameter and Depth

Post Height	Min Footing Diameter	Min Depth (excl. frost)	60 lb Bags Needed
Up to 6 ft	10"	24"	2-3
6-8 ft	12"	36"	4-5
8-10 ft	12-16"	42"	6-8

Pouring and Setting the Post

Mix concrete per the bag instructions (a 60 lb bag yields 0.45 cu ft). Pour into the tube form, insert the post to the correct depth, check plumb in both directions, and brace before the concrete sets. Do not load the post for at least 24-48 hours — 7 days for full structural loading.

Related Guides

• How to Install a Ledger Board on Concrete — The other critical deck-to-concrete connection
• Anchor Spacing and Edge Distance — Minimum requirements per ACI 318-19
• How to Mix Concrete by Hand — Step-by-step for footing pours
• Types of Concrete Anchors — Wedge, epoxy, and sleeve anchor guide
• Post Hole Calculator — Depth, bags, and frost depth by region
• Anchor Specification Engine — Get the exact anchor spec for your post base

Frequently Asked Questions

Can I attach a deck post directly to a concrete slab?

Yes — using a surface-mounted post base like the Simpson ABA or ABU series. The base is anchored to the slab with 1/2" wedge anchors or epoxy anchors, and the post sits in the base above the concrete surface. The slab must be at least 3.5" thick for adequate anchor embedment. Do not set posts directly on concrete without a base — moisture wicks up and rots the end grain rapidly.

How deep should deck post footings be?

Footings must extend below the frost line for your region plus an additional 6-12" of bearing depth below frost. In Toronto (48" frost depth), a deck post footing should be 54-60" deep minimum. Use our Post Hole Calculator for your specific city.

What is the best post base for a deck?

Simpson Strong-Tie ABA (adjustable) and ABU (uplift-rated) post bases are the industry standard. They have published ICC-ES ESR load values, are available in all common post sizes (4x4, 4x6, 6x6), and are accepted by building inspectors across North America. Use the ABU series for high-wind or seismic applications where uplift resistance is required.

How many concrete bags do I need per deck post footing?

For a 12" diameter footing 36" deep: approximately 4-5 bags of 60 lb concrete. For a 10" diameter footing 24" deep: 2-3 bags. Use our Post Hole Calculator for exact quantities by hole diameter and depth.