How to calculate bearing area.
Bearing area = bearing reaction ÷ allowable bearing pressure. The reaction comes from the structural engineer's beam schedule (in kN). The allowable bearing pressure depends on the masonry — typically 0.4 N/mm² for 7N/mm² blockwork, 0.6 for 10N/mm², and higher for engineering brick. Eurocode 6 (BS EN 1996) is the design route.
Worked example: a 60kN reaction onto 7N blockwork (0.4 N/mm² allowable). 60,000 N ÷ 0.4 N/mm² = 150,000mm² = 150 cm². A 327×215mm (13"×8") padstone gives 70,300mm² of bearing — not enough. Step up to a 440×215mm (17"×8"): 94,600mm² — still not enough. Go to a 440×440mm (17"×17") bespoke or specify higher-strength masonry.
Once the bearing area is set, the padstone height is driven by load spread (1:2 from the beam edge) and by Eurocode 6 limits on the masonry directly under the padstone. We design every WCCP padstone to that calc.
Schedule of typical padstone sizes.
| Size (LxWxH) | Bearing area | Typical use | Weight |
|---|---|---|---|
| 215×215×100mm (8"×8"×4") | 46,225 mm² | Lintel ends, light loads | ~11 kg (24 lb) |
| 327×215×100mm (13"×8"×4") | 70,305 mm² | Domestic UB / UC ends | ~17 kg (37 lb) |
| 327×215×140mm (13"×8"×6") | 70,305 mm² | Domestic UB ends, heavier load | ~24 kg (53 lb) |
| 440×215×100mm (17"×8"×4") | 94,600 mm² | Larger UB, two-storey loads | ~23 kg (51 lb) |
| 440×215×140mm (17"×8"×6") | 94,600 mm² | Two-storey loft conversions | ~32 kg (71 lb) |
| 440×215×215mm (17"×8"×8") | 94,600 mm² | Heavy commercial loads | ~50 kg (110 lb) |
| Bespoke | Schedule | Engineer's spec | To order |
All WCCP padstones cast in C40/50 to BS 8500-1:2023; bespoke sizes to your engineer's drawing.
What the engineer needs on the drawing.
A clear padstone callout names the size, the concrete grade and the bearing detail in one line. "440×215×140 (17"×8"×6") padstone, C40/50, on 7N blockwork, 100mm (4") bearing on the beam each side" tells the bricklayer everything. Where the load is high, add a Mortar Class M12 specification under the padstone.
Pocket details — where the padstone is cast into a wall rather than bedded on top — need a section drawing with dpc and movement-joint detail. We will cast pocket padstones to the engineer's drawing.
Standards on the spec sheet.
- BS EN 1996 (Eurocode 6) — bearing pressure and concentrated load checks.
- BS EN 1992-1-1 (Eurocode 2) — concrete design.
- BS 8500-1:2023 — concrete specification (C40/50 standard).
- BS EN 13369 — factory production control on every casting.
Common mistakes.
- Under-spec'd size. Picking a padstone by what's on the lorry instead of by the bearing calc. Localised crushing of the masonry under-spreads the load and cracks the wall.
- Wrong concrete grade. A C25 padstone under a C40/50 calc is a real-world site error — and a notifiable defect.
- No movement joint. Padstones that span across a wall expansion joint need to be split. Don't bridge the joint.
- Padstone too short for the beam flange. The padstone must exceed the flange width by at least 25mm (1") each side, or the bearing is offset.
- Bedding on weak mortar. Class M4 mortar under a heavy reaction will fail before the padstone does. Use M12 under loaded padstones.
Frequently asked questions
How do I calculate padstone size for a steel beam? +
Divide the bearing reaction (in kN) from your structural engineer by the allowable bearing pressure of the masonry beneath (typically 0.4–0.6 N/mm² for standard blockwork). The answer is the bearing area in mm². Choose a padstone whose plan dimensions exceed both the beam flange width and the calculated area.
What is a typical padstone size for a domestic beam? +
For a 152×152 UC carrying a single floor and roof in a domestic loft conversion, a 327×215×100mm (13x8x4in) or 440×215×140mm (17x8x6in) padstone is typical. Beams under bigger loads — say a UB203×133 carrying two floors — usually call for 440×215×215mm (17x8x8in). Always check against the engineer's reaction.
What concrete strength should a padstone be? +
C40/50 to BS 8500-1:2023. Lower grades have been used historically but Eurocode 6 bearing checks assume a strong, low-permeability concrete. We cast every WCCP padstone in C40/50 as standard.
Do padstones need reinforcement? +
Standard sizes are unreinforced — the unit acts as a plain concrete spreader. Larger padstones (over 215mm (8in) thick or carrying very high reactions) are reinforced to a structural calc, with cover and bar spacing to BS EN 1992.
What is the schedule for typical UK padstones? +
WCCP standard sizes start at 215×215×100mm (8x8x4in) and run through 327×215×100 (13x8x4in), 327×215×140 (13x8x6in), 440×215×100 (17x8x4in), 440×215×140 (17x8x6in) and 440×215×215mm (17x8x8in). Bespoke sizes — including beam-bearing pockets — are quoted from your beam schedule.
Need padstones to a beam schedule?
Send the schedule. We will check the sizes against the reactions, cast in C40/50, and deliver in load order.