Where do anchor bolts sit on a New Brunswick garage slab?

Anchor bolts in a New Brunswick garage slab are embedded in the concrete at the perimeter of the slab, positioned to pass through the pressure-treated sill plate (also called the mud sill) that sits on top of the concrete and ties the wall framing to the foundation.

The standard placement puts anchor bolts 6 inches from each corner and no more than 6 feet apart along each wall line — though many NB contractors space them at 4 feet for added rigidity, particularly on the wall lines that carry the most lateral load. Each bolt must be embedded a minimum of 7 inches into the concrete to develop adequate pull-out strength. The bolts project roughly 2.5 to 3 inches above the slab surface — enough to pass through the sill plate and accept a washer and nut with room to torque down properly.

The bolt diameter matters too. Half-inch (½") anchor bolts are the standard for residential garage sill plates in NB. Some contractors use 5/8-inch bolts at corners and at the sides of garage door openings where lateral forces concentrate, and this is good practice given NB's wind uplift conditions — particularly in coastal communities around Saint John, Shediac, or the Bay of Fundy shore.

Timing and Placement During the Pour

Anchor bolts are set while the concrete is still wet, immediately after screeding and before the surface is finished. This is a critical coordination point — the framing layout must be known before the slab is poured so the bolts land in the right position relative to the wall lines. A bolt that ends up under where a garage door track needs to mount, or too close to the edge of the sill plate, creates real problems during framing.

The bolts are typically held in position using a layout template — a piece of lumber or plywood cut to match the sill plate width with holes drilled at the correct spacing. The template keeps the bolts plumb and at consistent height while the concrete sets. Bolts that are set crooked or at inconsistent heights make sill plate installation frustrating and can compromise the connection.

The Sill Plate Connection

In NB, the sill plate must be pressure-treated lumber — no exceptions. Concrete wicks moisture, and untreated wood in direct contact with a concrete slab will rot within a decade in our climate. A standard 2x6 PT sill plate is common for 2x6 wall framing (which is the right choice for any insulated NB garage). The anchor bolt holes are drilled through the sill plate slightly oversized — typically 9/16" for a ½" bolt — to allow minor adjustment during layout.

A sill gasket (a thin foam or rubber strip) between the concrete and the pressure-treated plate is worth including. It seals the joint against air infiltration and moisture, which matters in NB's climate where cold air finding its way under the sill plate will undermine any insulation you've installed in the walls above.

Garage Door Opening Zones

Along the wall where the overhead garage door is installed, anchor bolt placement needs to account for the door track hardware and the bottom bracket. The bottom corner bracket for a standard sectional door sits very close to the floor on each side of the opening. Coordinate bolt placement so nothing conflicts with track mounting — your garage door installer will thank you.

When to Hire a Pro

Anchor bolt layout is one of those tasks that looks simple but has real consequences if done wrong. A bolt that's out of position by an inch can throw off wall alignment across the entire garage. If you're managing a self-build or acting as your own general contractor, have your framing layout fully drawn out before the concrete crew arrives, and walk through the bolt placement with them before the pour starts. Once the concrete cures, your options for correction are limited to epoxy anchor systems — which work, but add cost and a step that's entirely avoidable with good planning upfront.

Need help finding an experienced garage contractor in your area? New Brunswick Garages can match you with local builders through the New Brunswick Construction Network — browse the directory at newbrunswickconstructionnetwork.com.