Complete Guide to Safe and Stable Temporary Support with classic shoring and scaffolding setup for a cast-in-place concrete slab:
Step-by-Step Guide for Safe and Solid Temporary Support
Pouring a cast-in-place concrete slab or roof requires a temporary support system strong enough to carry the heavy load of fresh concrete, reinforcement steel, and workers. Two of the most common components of a safe shoring setup are steel adjustable jack posts and scaffolding. Here’s how these elements work together and how to install them correctly.
—
The Shoring Stack
From bottom to top, a typical assembly looks like this:
1. Concrete Floor or Footing – A solid, level base that can safely transfer the slab’s weight to the ground.
2. Steel Adjustable Jack Posts – Vertical posts that provide primary load support and fine height adjustment.
3. Primary Beams (4×4 or engineered) – Horizontal members that distribute loads to multiple posts or scaffold frames.
4. Plywood Decking – The flat surface forming the underside of the slab.
5. Steel Reinforcement (Rebar) – Tied into a grid and supported on chairs to maintain proper concrete cover.
6. Fresh Concrete – Poured on top, with weight transferring down through the entire stack.
—
Step 1: Planning the Layout
Jack Posts: Commonly spaced at about 4 ft × 4 ft (1.2 m × 1.2 m) for a 6-inch (150 mm) slab, though thicker or heavier pours may require closer spacing.
Scaffolding Frames: Used along edges or large spans, typically spaced 5 ft (1.5 m) apart horizontally and vertically braced according to the manufacturer’s tables.
Always follow an engineer’s design and local building codes.
—
Step 2: Preparing the Base
Clear and level the floor.
Place steel base plates or sole pads under jack posts and scaffold legs to distribute weight evenly.
For outdoor or soft ground, use heavy-duty mudsills or concrete pads.
—
Step 3: Installing Scaffolding
1. Set Base Plates or Screw Jacks on each scaffold leg.
2. Assemble First Level Frames and cross braces, checking for plumb and level.
3. Stack Additional Levels as needed, locking each with pins or couplers.
4. Add Diagonal Bracing to prevent sway.
5. Install Guardrails and Plank Decking if the scaffold will be used as a working platform.
6. Tie to the Structure if height exceeds manufacturer’s free-standing limits.
—
Step 4: Installing Jack Posts
1. Position jack posts between scaffold frames or in independent grids.
2. Extend each post until the top plate contacts the beam.
3. Use the screw collar for final tightening—snug but not forced.
4. Lock the adjustment nut and check plumb.
—
Step 5: Decking, Reinforcement, and Pour
Lay plywood sheets across the primary beams and scaffold ledgers.
Tie rebar and place chairs to maintain correct concrete cover.
Re-check plumb and tighten connections before placing concrete.
Pour and finish the slab while continuously monitoring the shoring.
—
Removal and Curing
Leave jack posts and scaffolding in place until the slab reaches engineer-specified strength—typically 7–14 days for residential projects.
Remove in stages, starting with rebar chairs and decking, then scaffold braces and posts.
—
Safety Tips
Load Ratings: Confirm jack post and scaffold capacities at the working height.
Bracing: Use cross and diagonal braces on scaffolding for lateral stability.
Inspection: Check plumb, tightness, and locking mechanisms before every pour.
PPE: Hard hats, gloves, and fall protection are essential when working at height.
—
Final Thoughts
Combining steel adjustable jack posts with properly braced scaffolding provides a flexible, reusable support system for concrete slabs and roof pours. With careful planning, solid footing, and consistent inspection, you can create a temporary structure capable of carrying the full weight of fresh concrete until the slab is strong enough to stand on its own.