FSC

Home & Construction

Foundation Scenario Comparison Calculator

Compare two foundation scenarios by volume, concrete, reinforcement, labor, fixed adjustment, total cost, and exact cost and quantity differences.

Foundation plan area (m²)Scenario A thickness (m)Scenario B thickness (m)Scenario A concrete price per m³Scenario B concrete price per m³Scenario A rebar kg/m³Scenario B rebar kg/m³Rebar price per kgPlacement labor per m³Scenario B additional fixed cost

Scenario A concrete volume-

Scenario B concrete volume-

Scenario A concrete cost-

Scenario B concrete cost-

Scenario A rebar cost-

Scenario B rebar cost-

Scenario A modeled total-

Scenario B modeled total-

Scenario B minus A cost-

Scenario B minus A volume-

Decision view

Foundation scenario dumbbell comparison

Foundation scenario dumbbell comparisonScenario A and B endpoints expose changes in volume, concrete, reinforcement, and total modeled cost.

Exact scenario comparisonScenario B thickness (m) changes while all other entered assumptions remain constant.

Scenario B thickness (m)	Scenario A concrete volume	Scenario B concrete volume	Scenario A concrete cost	Scenario B concrete cost	Scenario A rebar cost	Scenario B rebar cost	Scenario A modeled total	Scenario B modeled total	Scenario B minus A cost	Scenario B minus A volume

How to use Foundation Scenario Comparison Calculator

Enter the shared plan area.
Enter thickness, concrete price, and rebar intensity for both scenarios.
Enter shared rebar and labor rates plus scenario B's fixed difference.
Compare component endpoints and totals without treating either scenario as structurally approved.

Calculator guide

Understanding Foundation Scenario Comparison Calculator

Foundation alternatives must be costed independently before their difference is interpreted. Thickness changes volume, reinforcing intensity changes steel weight, and a scenario-specific fixed adjustment can shift the result even when a material unit price is lower.

Independent totals Each scenario is priced separately.

Quantity and rate differ Lower unit price may not mean lower cost.

Fixed delta is visible Scenario B adjustment is isolated.

Comparison is not design Engineering suitability remains external.

Calculation method

How the calculation works

Calculate each scenario's volume, concrete, reinforcement, labor, and fixed adjustment independently before comparing exact totals and material quantities. Calculate each scenario's volume and component costs independently from the same plan area, then subtract scenario A from scenario B.

Detailed calculation process

Compare two foundation quantity-and-cost scenarios

The default compares 0.15 m and 0.20 m slabs over 180 m², with different concrete prices and reinforcing intensities plus $2,500 additional fixed cost in scenario B.

General formula: V_j=Ad_j; C_j=V_jp_j+V_jq_jp_r+V_jp_l+F_j; Delta C=C_B-C_A; Delta V=V_B-V_A, for j in {A,B} Each scenario uses its own thickness, concrete price, and rebar intensity. Rebar price and labor rate are shared. Only scenario B receives the entered fixed-cost difference before totals are compared.

What each symbol means

A, d_j, V_j Plan area (m²), scenario thickness (m), and concrete volume (m³).

p_j Scenario concrete price (currency/m³).

q_j, p_r Scenario rebar intensity (kg/m³) and shared rebar price (currency/kg).

p_l, F_j Shared labor rate (currency/m³) and scenario fixed adjustment (currency).

C_A, C_B Modeled totals for scenarios A and B (currency).

Delta C, Delta V Scenario B minus A cost (currency) and volume (m³).

Worked substitution with the default inputs

1. Calculate scenario volumes: V_A=180*0.15=27 m³; V_B=180*0.20=36 m³; Delta V=9 m³ Both scenarios use the same plan area, so thickness creates the volume difference.

2. Price concrete: A: 27*$145=$3,915; B: 36*$138=$4,968 B has a lower unit price but a larger quantity.

3. Price reinforcement: A: 27*80*$1.30=$2,808; B: 36*105*$1.30=$4,914 Both volume and rebar intensity are higher in scenario B.

4. Add labor and fixed adjustment: labor A=27*$78=$2,106; labor B=36*$78=$2,808; fixed A=$0; fixed B=$2,500 The fixed difference is added only to scenario B.

5. Compare totals: C_A=$3,915+$2,808+$2,106=$8,829; C_B=$4,968+$4,914+$2,808+$2,500=$15,190; Delta C=$6,361 Both dumbbell endpoints are calculated before subtraction.

Scenario B uses 9 m³ more concrete and costs $6,361 more than scenario A under the entered component assumptions.

Alternative comparison

Use a component dumbbell instead of generic boxes

Each row connects scenario A and B so both the direction and magnitude of change remain visible.

Volume row Thickness drives material quantity.

Concrete row Unit rate and volume combine.

Rebar row Intensity adds another driver.

Total row Labor and fixed cost complete the gap.

Worked situations

Practical examples

Scenario A uses 27 m³ and totals $8,829.
Scenario B uses 36 m³ and totals $15,190.
The exact modeled difference is $6,361 in favor of scenario A.

Better inputs

Useful tips

Keep both scenarios at the same scope boundary.
Use separate engineering takeoffs when structural systems differ.
Compare performance and constructability alongside initial cost.

Before relying on the result

Limitations and common mistakes

The arithmetic does not establish structural equivalence.
Soil, loads, reinforcement detailing, cracking, durability, excavation, and code are excluded.
Only scenario B has an explicit fixed-cost adjustment field.

Reference

Key terms

Rebar intensity: Entered reinforcing mass per cubic metre.
Scenario delta: Scenario B result minus scenario A result.
Scope boundary: The set of cost components included consistently in both alternatives.

Important note

Calculated from the entered measurements and stated coverage or quantity rules. Confirm field dimensions, waste, product requirements, structural conditions, and local codes before purchasing or building.

Frequently asked questions

Why is B concrete cost higher despite a lower price per m³?

Its 36 m³ volume is one-third larger than A's 27 m³ volume.

Does the $2,500 fixed difference affect A?

No. The field is defined as an additional scenario B cost.

Can I compare two structural systems?

Only if the entered quantities and scope are genuinely comparable and both have been designed appropriately.

Why show component gaps?

They reveal which assumptions create the total difference.