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What They Are, How They're Used, How to Install H20 Beams
2026-08-12
H20 wood beams. Common formwork component. Residential and mid‑rise concrete work. I‑shaped timber beams. Support slabs, beams, Wall Formwork. Good balance of strength, weight, and cost.
What They Are
Engineered timber. I‑shaped cross‑section. 200mm high. 80mm wide at flanges.
- Spruce or pine.
- Waterproof glue lines.
- Web thickness: 26‑30mm.
- Flanges provide stable surface for plywood.
- Standard lengths: 2.5m to 6.0m.
- Designed for repeated use. Proper maintenance extends life.
Main Uses
- Supporting Slab Formwork.
- Multi‑storey residential and commercial.
- Carrying wall and beam forms.
- Creating temporary decks and working platforms.
- Bridging between props.
Popular on mid‑rise projects. Light enough to handle manually. Strong enough for typical floor loads.
Spacing? Usually 400‑600mm centers. Depends on slab thickness and concrete load. For a 150mm slab, 500mm spacing works. For 200mm slab, drop to 400mm.
Recent Project Example
Melbourne. 8‑storey apartment building. Completed last quarter.
Used H20 beams for all slab formwork. Spaced at 450mm. Supported 180mm slabs. Crew of six set up each floor in about 4‑5 hours. That's with props, beams, and plywood decking.
Project manager said H20 beams saved about 20% on setup time compared to steel joists.
How to Install
Straightforward process.
1
Prepare supports – Adjustable props positioned per layout.
2
Place primary beams – Lay H20 beams across props at required spacing. Beams sit securely on prop heads. Timber or steel cap helps distribute load.
3
Add secondary members if needed – Smaller joists perpendicular to main beams.
4
Lay formwork panels – Plywood or other sheets fixed on top. Nail or screw into flanges.
5
Check levels and bracing – Adjust for level. Brace properly before pouring.
6
Strip after concrete gains strength – usually 3‑5 days for slabs. Remove panels. Lower beams and props carefully. Clean beams. Inspect for damage. Store flat to maintain shape.
Cost Reality
H20 beams cost more upfront than solid timber joists. But they last longer. 20‑40 uses vs 5‑8 uses for solid timber. Cost per use works out lower.
One contractor ran the numbers:
€3.20 H20 beams per use
€5.50 Solid timber per use
Plus less waste disposal.
Why Contractors Keep Using Them
- Relatively lightweight.
- Easy to cut and adjust on site.
- Compatible with standard plywood.
- More economical than aluminum or steel for many jobs.
- End seals protect from moisture.
- Store flat, off the ground, covered from rain.
- 20‑40 reuse cycles typical with good care.