Attaching Fence Posts to a House and Concrete Surface

When you need to screen a small side yard bounded by the house on one side and an existing wooden fence on the other, the challenge is securing new fence posts to both the house wall and a concrete slab. The following methods cover the most reliable approaches for a durable installation.

Fastening a Post to the House Wall

Cut the post to length, leaving a 1-inch clearance at the bottom to prevent capillary moisture uptake. For a nominal 4×4 post (actual 3.5″), use 6- to 7-inch hot-dipped galvanized lag bolts. Pre-drill clearance holes through the post and into the house framing—never rely on siding alone. Inject clear silicone caulk into the house-side holes before driving the bolts to seal against water intrusion. Two or three bolts spaced vertically will provide a solid connection.

Critical check: Verify that no electrical, plumbing, or gas lines run through the wall at the attachment point. Corners are generally safest because framing members are doubled there.

Setting a Post in the Ground Adjacent to the Foundation

If you prefer not to bolt to the house, excavate beside the foundation, carefully chipping through the footing with a hand sledge (avoid heavy equipment to prevent footing cracks). Set the post base at least 18 inches deep, plumb it against the house wall, and backfill with concrete. Keep the post within 4 inches of the wall for a clean look.

Anchoring Posts on an Existing Concrete Slab

You have three main options:

• Core drilling: Hire a concrete-cutting company to core 6-inch-diameter holes through the slab. Costs typically start around $200.
• DIY core drilling: Rent a core-drill rig from a tool rental yard. This is physically demanding and best suited for those in good condition.
• Cut-and-chisel method: Use an old circular saw with a masonry blade to cut a square outline (8–12″ per side) through a 3–4″ slab. Chisel out the center, then dig a post hole below. This leaves a rough appearance but works for utilitarian projects.

Surface-Mounted Post Anchors

If the post is braced at the top (e.g., by a horizontal rail) and doesn’t need to resist lateral loads, a surface-mounted post anchor is simplest. Drill a hole in the concrete, inject a two-part construction epoxy, set the anchor, and fasten the post. Simpson Strong-Tie and other manufacturers offer dozens of anchor styles; search “post anchors” or “attaching posts to concrete” for specifics.

Whichever method you choose, ensure all hardware is hot-dipped galvanized or stainless steel for longevity. Good luck with your project.