Floor Beam & Block Calculator — Beams, Blocks & Topping

For a standard 150mm prestressed T-beam with 440×215×100mm infill blocks, beams sit at 530mm centres (615mm for the wide-spacing option). Divide the run length (the dimension the beams are laid out along) by 0.53 and add 1 for the end beam. A 6m run needs ceil(6 ÷ 0.53) + 1 ≈ 13 beams. Always confirm the centre spacing against your beam and block manufacturer's load/span tables.

Standard 440×215×100mm infill blocks bridge the gap between beams: at 530mm centres the 440mm block face spans the ~420mm clear gap, bearing on each beam flange (each block is rated to carry at least 3.5kN over a 420mm span). Along the beam run, blocks repeat every 215mm. So a 5m beam run needs 5000 ÷ 215 ≈ 24 blocks per bay, and a typical floor works out at roughly 9–10 blocks per m².

Often, yes. A 65mm structural topping (concrete or sand:cement screed, reinforced for garages or high point loads) is commonly applied over the beams and blocks to tie the floor together, level the surface and improve robustness. Some manufacturer systems are designed to perform without a structural topping under standard domestic loading — check the specific system's design certificate before omitting it.

Most beam and block manufacturers require temporary propping at mid-span while the blocks are laid and the topping is poured — typically one prop row at mid-span for spans up to about 4m and two rows for longer spans. Props are removed once the topping has cured to full strength. Follow your manufacturer's installation guide for the exact propping layout.

Standard prestressed concrete floor beams can span up to about 6m for domestic loading. Beams should span the shorter plan dimension. Longer spans require deeper beams or an intermediate load-bearing support (sleeper wall). Check manufacturer span tables for the specific beam type and loading.