Setting Heavy-Duty Steel Gate Posts in Concrete with Rebar Cages
Step-by-step guide made from Indy Farm Life's YouTube video.
Install 6x6-inch, 12-foot steel gate posts in 4-foot-deep holes to support 300-pound driveway gates. The posts are set on a gravel drainage base, braced plumb, reinforced with custom-tied rebar cages, and anchored in nearly 6 cubic yards of fiber-reinforced concrete.
The full step-by-step Spetz Specs for this project (every part, size, diagram and step, free): Setting Heavy-Duty Steel Gate Posts in Concrete with Rebar Cages Spetz Specs.
- Difficulty: intermediate
- Finished size: 6 in x 6 in x 12 ft steel posts set in 4 ft deep holes
Safety
- Locate all underground electrical, communication, and sewer lines before excavating, and hand-dig within the tolerance zone of marked utilities.
- Wear safety glasses and work gloves when cutting steel rebar with a portable band saw or driving bracing stakes with a sledgehammer.
- Use mechanical lifting equipment such as tractor pallet forks and a helper to maneuver heavy 12-foot structural steel posts into deep holes.
- Wear waterproof rubber boots and gloves when working with wet ready-mix concrete to prevent skin irritation and chemical burns.
Must know before you build
- Weld angle iron to post base for concrete anchor, preventing twist/pull-out.
- Paint underground steel with oil-based enamel to prevent subterranean corrosion.
- Embed rebar into the wet concrete along the narrow driveway side of the post to help prevent that edge from cracking.
- Hand-dig near marked utility lines; machine excavation risks severing buried services.
- Re-check braced posts for plumb after rain; settled soil can throw alignment before pour.
Tools
- Backhoe loader (tractor loader backhoe, Case) (optional)
- Shovel (round-point digging shovel)
- Compact utility tractor with loader and pallet forks (compact utility tractor, John Deere, 4105) (optional)
- Stepladder (fiberglass A-frame stepladder)
- Tape measure (retractable blade tape measure)
- Sledgehammer (long-handle sledgehammer)
- Magnetic post level (multi-axis magnetic post level)
- Portable band saw (corded portable deep-cut band saw, Harbor Freight)
- Leaf blower (handheld leaf blower) (optional)
- Cordless drill/driver (battery-powered cordless drill/driver, Ryobi)
- Concrete finishing trowel (rounded-end hand float / trowel)
Materials
- Steel gate posts with welded angle iron (2, square structural steel tubing, 1/4 in wall thickness, custom welded angle-iron crossbars, 6 in x 6 in x 12 ft)
- Ready-mix concrete (6 cubic yards, fiber-reinforced ready-mix concrete, with fiber reinforcement)
- Rebar (deformed steel reinforcing bar)
- Black oil-based paint (oil-based protective enamel, black)
- 2x4 lumber (dimensional framing lumber, 2 in x 4 in)
- Crushed gravel (#2 stone) (1 tractor bucket, crushed stone drainage aggregate, #2 stone)
- Exterior screws (construction screws)
- Wooden stakes (wood form stakes)
- Steel fence post (T-post) (1, studded steel T-post)
- Rebar tie wire (annealed steel tie wire)
- Plywood sheathing (OSB / plywood form board)
Step by step
Step 1: Add a Gravel Drainage Base to the Post Holes
Clean loose soil out of the excavated post holes and pour a layer of crushed gravel into the bottom of each hole for water drainage.
- Haul and dump crushed gravel into the post holes. Clean loose dirt from the bottom of both 4-foot post holes, haul a loader bucket of crushed gravel to the driveway, and dump a layer of stone into the bottom of each hole.
- Tip: Add a layer of crushed gravel to the bottom of each hole before setting the post so water drains away instead of corroding the steel base.
Step 2: Set and Brace the Steel Posts in the Holes
Transport the 12-foot steel posts to the holes, stand them upright on the gravel base, and secure them with 2x4 collars and diagonal braces.
- Transport the steel post on a tractor pallet fork. Slide the hollow 6x6 steel post onto one tine of the tractor's pallet forks and drive it down the driveway to the excavated hole.
- Tip: Slide the hollow square steel post over a single pallet fork tine to transport and position heavy posts safely.
- Tip the steel post upright into the hole. Position the base of the post over the hole, raise and tilt the tractor pallet forks while guiding the top by hand until the post slides off the fork onto the gravel base, and rotate it upright in the hole.
- Watch out: Keep hands and feet clear of the bottom of the trench while sliding the heavy steel post off the tractor forks into the hole.
- Prop the post with a 2x4 brace and adjust its position in the hole. Hold the post upright in the hole, lean a 2x4 brace assembly against it for temporary support, and tap the welded angle iron at the bottom of the post with a sledgehammer to rotate and adjust its position in the trench.
- Tip: Put on safety glasses before striking the welded angle iron at the base of the post with a sledgehammer.
- Tip: If rocky soil or #2 stone prevents driving wooden stakes into the ground, drive a steel T-post into the ground and screw a wooden scab board to it to anchor the 2x4 post braces.
- Tip: Build a wooden collar around the upper section of the steel post so diagonal 2x4 braces can hold the post without drilling holes in the steel.
Step 3: Adjust Post Spacing and Trench Sidewalls
Measure the span between the two posts across the driveway and shave back the trench sidewall with a shovel to bring the posts to the exact required spacing.
- Measure the span between posts and shave the trench sidewall. Stretch a tape measure across the driveway between the two posts to check the gate opening width, then use a shovel to shave soil off the inner trench sidewall so the welded angle iron clears the dirt and the post shifts inward to the proper span.
- Tip: Stretch a tape measure between both posts before tying rebar or pouring concrete to verify the exact gate opening width.
Step 4: Build the Rebar Cages and Prep the Footings for Concrete
Cut steel rebar to length using a portable band saw, lay the bars into the excavated holes around the post anchors, and tie them into a 3D grid cage. Then block off the unused end of each trench with a plywood form and clear debris out of the holes before the pour.
- Cut rebar to length with a portable band saw. Brace a length of steel rebar across the tractor box blade and cut it into sections for the footing cage using a corded portable band saw.
- Tip: Use a portable band saw to cut rebar quickly and cleanly in the field.
- Watch out: Wear eye protection and gloves when cutting steel rebar with a portable band saw.
- Lay and tie the rebar cage in the post hole. Place longitudinal, transverse, and vertical rebar pieces into the excavated trench around the post's welded angle-iron crossbars and bind the intersections with tie wire to form a 3D rebar cage.
- Tip: Interlock the rebar cage around the welded angle-iron crossbars on the post so the steel post is mechanically tied into the reinforced concrete mass.
- Block off unused trench with plywood and clear the holes. Stand a piece of plywood across each trench where the concrete pad doesn't need to extend, backfill dirt behind it so the pour stops at the form, and blow leaves and debris out of the bottom of the holes and rebar cages with a leaf blower.
- Tip: Use a plywood form and backfill to stop the pour where you don't need concrete yet; you can pour an opener pad there later once you know where it goes.
- Tip: Blow leaves and loose debris out of the holes and rebar cages right before the concrete truck arrives.
Step 5: Re-Plumb the Posts and Reinforce Bracing
Check the posts with a magnetic post level, adjust the screw-fastened 2x4 braces until plumb, and drive an additional wooden stake with a sledgehammer to reinforce the bracing.
- Adjust the 2x4 braces using a magnetic post level. Stick a magnetic post level onto the steel post, back out the screws on the upper 2x4 collar and diagonal braces with a cordless drill, shift the post until both vials read plumb, and drive the screws back in.
- Tip: Use a magnetic post level on steel posts to keep both hands free for adjusting the bracing and driving screws.
- Common mistake: Assuming posts that were plumbed a week earlier are still plumb on pour day without re-checking after rain.
- Drive an extra stake and attach a third diagonal 2x4 brace. Drive a wooden stake into the ground next to the hole using a sledgehammer and screw a diagonal 2x4 brace from the stake up to the upper collar on the steel post to eliminate wobble before the pour.
- Tip: Add an extra stake and cross-brace to any post that feels wobbly before the heavy force of pouring concrete hits the hole.
- Common mistake: Over-driving a wooden stake with a sledgehammer until the top of the wood splinters apart.
Step 6: Pour Concrete into the Post Footings
Direct the ready-mix concrete chute into both post holes to completely encase the rebar cages and steel posts, spreading the mix level with a shovel.
- Pour ready-mix concrete into the first post footing. Position the ready-mix concrete truck chute over the first post hole and discharge fiber-reinforced concrete until it fills the bottom post hole, covers the rebar cage, and reaches the top of the plywood form.
- Pour and shovel concrete into the second post footing. Swing the concrete truck chute to the second post hole, fill the excavation with concrete, and spread the concrete evenly around the post and form edges using a shovel.
- Tip: Have spare 5-gallon buckets or a small wooden form ready on site to catch leftover ready-mix concrete from the truck.
Step 7: Embed Top Rebar and Trowel the Concrete Pads
Press additional lengths of rebar into the top surface of the wet concrete and float both post pads smooth and level with a hand trowel.
- Press rebar into the spare form and trowel smooth. Lay cut pieces of rebar on top of the wet concrete in the spare wooden form, push them down into the mix with a hand trowel, and float the surface smooth.
- Embed rebar and trowel the two gate post pads level. Press a length of rebar into the wet concrete along the narrow inner side of the gate post and work a hand trowel in sweeping arcs around both posts to level and smooth the concrete pads.
- Tip: Press a length of rebar into the wet concrete along the narrow side of the post to help prevent that thinner section of concrete from cracking.
- Tip: Trowel the top surface of the concrete footing flat and level so it can serve as a foundation pad for future brick columns.