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How to use the strip footing calculator

A wall footing per metre run: what each input means, how to read the bearing pressure, and why the page opens as NOT CHECKED until you give the exposure.

All guides Inputs Result Calc sheet Walk-through Mistakes

1. What the calculator does

The strip footing calculator designs a continuous footing under a wall, per metre run. It checks the bearing pressure under the footing for the wall loads (with a moment and a horizontal load if there are any), then designs the footing as reinforced concrete: bending at the face of the wall, shear, the main bars across the footing and the distribution bars along it.

The code routes are SANS 10100-1, BS 8110-1, Eurocode 2 (EN 1992-1-1) and SANS 51992-1-1 (SA Eurocode, 2023 draft annex). The page badge names the clauses: SANS 10100-1 cl. 4.10 for bases, cl. 4.3 for bending and shear and cl. 4.11 for detailing; on EN 1992-1-1, 6.1, 6.2 and 9.3; loads to SANS 10160-1.

Strip footing calculator header with the NOT CHECKED badge and the Give input button — The header as the page opens: NOT CHECKED, because the exposure is not stated yet. “Give input: Durability” and Go take you to the missing input.

2. The inputs, group by group

Input	What it means	Typical value
Footing	Design code, width B, depth h, wall width and the wall offset from the centre (for an eccentric wall).	B 0.9 m, h 0.3 m, wall 230 mm
Loads per metre run	Characteristic N, M and H per metre for dead G, imposed Q and wind W. The combination factor ψ for Q is the code value unless you type one.	G 60, Q 25 kN/m
Soil	Allowable bearing pressure q_a (SLS) and the depth of soil over the footing.	150 kPa, 0.5 m
Materials	Concrete f_cu and steel f_y.	30 MPa, 450 MPa
Bars	Main bars across the footing at the bottom, and distribution bars along the run: auto, or a size and spacing.	auto
Durability	Cover to the bottom bars and the exposure. “Not stated” leaves durability NOT CHECKED.	50 mm, cast against soil

Strip footing inputs: footing, loads per metre run, soil, materials, bars and durability — The inputs. Everything is per metre run of wall; the loads are characteristic.

3. How to read the result

The section draws the wall on the footing with the soil over it, the main bars across the bottom, the distribution bars and the bearing pressure under the footing at SLS. Here q_max is 108.3 kPa against an allowable 150 kPa.

Strip footing section with the bars and the bearing pressure — Section and bearing pressure: B 900 × h 300, main Y12 @ 275, distribution Y10 @ 200, q_max 108.3 kPa.

The badge shows the highest utilisation and names the governing check. As the page opens it reads NOT CHECKED: the exposure is “Not stated”, so the durability check cannot run, and a design with any NOT CHECKED item is not shown as a pass. Set the exposure and the badge changes to PASS or FAIL.

Design checks summary for the strip footing — Design checks: SANS 10100-1 · 8 pass · 1 not checked.

Design result card for the strip footing — The design result card: main and distribution bars, effective depth and the self-weight of footing and soil, and the ULS cases used.

Signed out, some rows of the design result card show a dash (“—”): the values behind each check, with their clauses, open when you sign in. The badge, the drawings and the bars are there for everyone. The results keep their numbers too (here q_max in the section); only the check rows hide their clauses and values. This is intended.

4. Calc sheet and schedule

The result (pass / fail and utilisation) stays free for everyone. Every check with its clause, the calc sheet and the bending schedule are open to signed-in users. Sign in free: 3 designs a month (one calculator, open for 24 hours). Unlimited with a calculator pack.

The bending schedule card reads: “Sign in (free): 3 schedules a month. CSV with a paid plan.” On the project board a strip footing follows the wall lines of the setting-out plan, with the corner and tee bars scheduled.

Bending schedule card for the strip footing — The bending schedule card.

5. A 2-minute walk-through

Open the calculator: a 230 mm wall on a 0.9 × 0.3 m strip, G 60 and Q 25 kN/m, 150 kPa soil.
The badge reads NOT CHECKED. Press Go next to “Give input” and set the exposure to cast against soil (or against soil, blinded).
Read the badge again: now PASS or FAIL, with the governing check named.
Raise Q to 60 kN/m and watch the bearing pressure; widen B until it passes.
Move the wall 150 mm off centre and see the pressure go uneven.
Sign in for the check values, the calc sheet and the schedule.

6. Common mistakes

Loads per wall instead of per metre. Divide the wall load by its length.
Ultimate loads in the load table. It takes characteristic G, Q and W; the engine builds the ULS and SLS combinations.
Reading NOT CHECKED as a fail, or ignoring it. It means an input is missing; give it.
Allowable bearing from a guess. Take q_a from the geotechnical report, and check the founding depth it applies to.
Too little cover. A footing cast straight against the soil needs more cover than one on blinding.

7. Where it fits

The wall loads come from a load take-down or the masonry wall calculator. For two columns on one base, use the combined footing calculator.

8. Learn more

Try it nowThe calculator opens with the walk-through inputs above. The result is free; sign in for the checks, calc sheet and schedule.
Open the strip footing calculator

A guide to using the calculator, not a design. Check every value against the current code and your own project, and have the design checked and signed by a registered professional engineer.

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