Decking, floor openings and landing loads

Metal deck is the corrugated steel sheet that spans between beams or joists to form floors and roofs. On the second and third floors of the classroom wing at the Prairie Gate Community Centre, the deck would later be filled with concrete to make composite floors. On the gymnasium roof, it would carry insulation and roofing. For the decking crew led by Kyle Bear, it was also the surface they stood on while they built it. Each sheet was about 0.9 m (3 ft) wide and up to 9 m (30 ft) long, light enough to carry but large enough to act like a sail in wind, and slippery when wet or frosty. Until each sheet was fastened down, it could slide, lift or tip under a worker's feet.

This lesson covers landing deck bundles on the frame, spreading and fastening deck, openings and covers, gaps at columns, perimeter safety cables, shear connectors, and the leading edge, where decking crews work at the edge of the deck they have just laid.

Landing deck bundles

Deck arrives in bundles of 20 to 40 sheets, banded together and weighing 1 to 2.5 t (1 to 3 tons). The bundles are hoisted onto the frame and landed on the beams or joists near where they will be spread. Landing bundles is one of the most dangerous moments in decking, for three reasons. A heavy bundle can overload the members it lands on, especially open-web joists. A bundle landed on too few supports can tip or slide when the bands are cut. And loose items on top of the bundle can fall during the lift.

Tallgrass's rules for landing deck, based on the erection plan and the joist manufacturer's instructions, were these. Bundles are hoisted only with the rigging designed for them, never by the packaging bands. Loose items on top of a bundle are secured before it is lifted. Bundles are landed only on framing that the erection engineer has confirmed can carry them, and only where the bundle has enough support to be unbanded without sliding off. On open-web joists, bundles are landed only after the bridging is installed and anchored and the joist bearing ends are attached, and only near a support line. At the end of each shift, or sooner if the wind picks up, any deck that has not been fastened is secured so it cannot move.

At the Prairie Gate Community Centre, the deck bundles for each floor were landed on the girders close to the columns, where the framing was strongest, on timber blocking that kept them off the beam flanges and let the slings come out. Bundles were never landed on the middle of a span of joists. Kyle's crew did not cut the bands until the bundle had been landed, released from the hook and checked to make sure it was stable.

Spreading and fastening deck

Deck must be laid tightly and fastened as soon as it is placed, so that it cannot slide, lift or be blown off. Kyle's crew spread sheets from the bundle, aligned them, and made the initial attachments at each support before moving on, then returned to complete the final fastening pattern shown on the deck drawings. The erection plan required at least two attachments per sheet at each end before anyone walked on it beyond the leading edge, and the full pattern by the end of the shift.

Deck is fastened with welds, powder-actuated pins, self-drilling screws or button punches at side laps. Powder-actuated tools must be used only by trained operators, following the tool manufacturer's instructions and the rules in HSE-104 and TRD-104. Welding deck puts welders at the leading edge with their attention on the arc, so their fall protection must not depend on them remembering it.

Openings in the deck

Every floor has openings: stairs, elevator shafts, mechanical shafts, roof drains and skylights. Openings can be framed so that the deck runs continuously over them and is cut out later, or left open with the deck stopped at the edges. A deck that runs continuously over an opening and is cut later is safer, because there is no hole until the trade that needs it is ready, and the hole can be protected when it is cut.

Any opening a worker could step into must be guarded or covered. Covers at the Prairie Gate Community Centre had to support at least twice the weight of the workers, equipment and materials that might be on them at one time, be secured so they could not be kicked or blown out of place, and be marked with the word HOLE or COVER or painted a high-visibility colour. Skylights and roof drains do not count as covers unless they can carry that load. These are the same requirements OSHA uses, and they protect workers from falling through openings as Manitoba's regulation requires.

Covers are a common cause of falls when they are removed and not replaced. At the Prairie Gate Community Centre, removing a cover required the foreman's permission and a guardrail or a worker stationed at the opening until the cover went back.

Gaps at columns

Deck sheets do not fit tightly around columns, leaving gaps that can be large enough for a foot or a person to go through. At the Prairie Gate Community Centre, every gap around a column was closed with wire mesh, plywood or a steel plate fastened in place as soon as the deck around the column was laid, so that no gap was left that a worker could fall through.

Perimeter safety cables

Once deck is laid on a floor, the outside edge of the floor becomes a fall hazard for everyone who follows the decking crew. At the Prairie Gate Community Centre, perimeter safety cables were installed around the exterior edge of each floor, and around large interior openings, as soon as the deck was in place. The cables met Manitoba's guardrail requirements: a top rail at the specified height, a mid rail, and strength to resist the load the regulation sets. Perimeter columns were supplied with holes or attachments for the cables, and the cables stayed until the permanent walls went in.

Shear connectors and the walking surface

The composite floors at the Prairie Gate Community Centre used shear studs welded through the deck to the beam flanges, so that the concrete and steel would act together. Studs sticking up from a beam flange are a serious tripping hazard for anyone walking along the beam. The erection plan required studs to be installed only after the deck was laid, using the deck as the working surface, and never by welding them to the beam flanges in the shop.

The leading edge

The leading edge is the unprotected edge of deck that moves forward as sheets are laid. The decking crew works right at it. Behind them is a growing area of deck; in front of them is open framing and a fall to the floor below.

Manitoba's regulation has no controlled decking zone, so decking crews on Tallgrass jobs work tied off or behind guardrails or nets above 3 m. At the Prairie Gate Community Centre, the decking crew wore full-body harnesses connected to self-retracting lifelines on a horizontal lifeline strung between columns above the work, designed by Sanjay Mehta, so they could work at the leading edge protected at all times. Lesson 9 covers the fall protection systems in more detail.

# End-of-shift deck check: unsecured area on the second floor (invented data).
sheets = [
    # sheet id, length (m), width (m), initial attachments made, full pattern done
    ("2-01", 9.0, 0.91, True, True),
    ("2-02", 9.0, 0.91, True, True),
    ("2-03", 9.0, 0.91, True, False),
    ("2-04", 9.0, 0.91, False, False),
    ("2-05", 6.0, 0.91, False, False),
]
loose = [(s, l * w) for s, l, w, initial, full in sheets if not initial]
partial = [s for s, l, w, initial, full in sheets if initial and not full]
area_m2 = sum(a for s, a in loose)
print("sheets with no attachments:", [s for s, a in loose])
print(f"unsecured area: {area_m2:.1f} m2 ({area_m2 * 10.764:.0f} ft2)")
print("sheets awaiting full fastening:", partial)
print("secure or remove loose sheets before leaving" if loose else "deck secured for the night")

sheets with no attachments: ['2-04', '2-05']
unsecured area: 13.6 m2 (147 ft2)
sheets awaiting full fastening: ['2-03']
secure or remove loose sheets before leaving

Weather and decking

Wind lifts deck sheets easily. At the Prairie Gate Community Centre, decking stopped at a lower wind speed than other erection work, set in the erection plan, and bundles were not opened when strong gusts were forecast. Frost, ice, snow and rain make deck slippery; the crew swept frost and snow off before walking on it and stopped work when the surface could not be made safe. In the hot weeks of summer, steel deck in direct sun gets hot enough to burn skin, so gloves and sleeves were required.

Deck as a working platform for other trades

Once a floor's deck is fastened, it becomes the working surface for other trades: concrete crews placing the slab, plumbers and electricians setting sleeves and boxes, and inspectors checking studs and fasteners. Deck that has not had its concrete placed is thin steel and cannot carry heavy concentrated loads. At the Prairie Gate Community Centre, the deck drawings listed the construction loads the bare deck could carry, and Rosa Delgado's coordination meetings made sure no trade landed heavy pallets, gang boxes or rebar bundles on the bare deck outside the areas marked for them. Concrete pump hoses and buckets were planned so they did not overload the deck before the slab was placed.

Deck edges and openings changed as trades worked. Electricians cut openings for floor boxes, plumbers cut holes for drains. Every new opening had to be cut only after a cover or guardrail was ready, and Tallgrass's hole permit made the trade that cut the hole responsible for covering it the same moment.