The BHS Animal & Plant Science Remodel is a single-story renovation project located in Bentonville, Arkansas, involving interior renovations and limited exterior modifications to an existing educational facility.
For this project, the foundation work scope is limited to selective foundation-related modifications, including:
- Slab demolition and replacement
- Edge thickening at slab infill
- Doweling into existing concrete
- Subgrade preparation
- Exterior sidewalk and slab edge support
- Minor concrete foundation restoration around new openings
The relevant structural and architectural drawings for foundation work include:
- S1.0 – Structural General Notes
- S3.1 – Structural Framing Plan
- A2.0 – Demolition Plan
- A2.1 – Floor Plan
- A2.2 – Architectural Details
This is not a new building foundation package, but rather a selective foundation restoration scope supporting plumbing modifications, slab infills, and minor exterior work.
This kind of renovation foundation work requires careful estimating because the quantities are small but the labor intensity, mobilization cost, and tie-in complexity are high.
2. TRADE ABSTRACT / SCOPE OVERVIEW
The foundation subcontractor scope includes:
A. Selective Demolition
- Sawcut existing slab at trench locations
- Remove slab sections for plumbing work
- Remove slab at infill locations
- Remove sidewalk at exterior modifications
Referenced in:
- A2.0 demolition notes
- S3.1 slab demo notes
B. Foundation Restoration
- Recompact subgrade
- Install vapor barrier
- Install reinforcing mesh
- Install dowels into existing slab
- Place new slab concrete
- Form slab edge repairs
- Repair slab around penetrations
Referenced in:
- A2.0 D9 slab infill detail
- S1.0 concrete notes
C. Accessories
- WWF reinforcement
- Dowels with epoxy
- Vapor barrier
- Edge forms
- Joint sealants
D. Labor & Equipment
- Saw cutting
- Concrete demolition
- Rebar doweling
- Forming
- Placement and finishing
3. PLAN REVIEW PROCESS
Step 1 – Review Structural Notes (S1.0)
The estimator begins by reviewing S1.0, which establishes:
- Concrete strength
- Reinforcing requirements
- Doweling requirements
- Subgrade preparation standards
This defines the required restoration materials.
Step 2 – Review Structural Framing Plan (S3.1)
On S3.1, the plan note states:
“Slab demo and pourback as required to remove and cap sanitary sewer lines.”
This identifies slab restoration quantities.
Step 3 – Review Architectural Demolition Plan (A2.0)
On A2.0, demolition notes and slab infill detail define:
- slab removal limits
- doweling
- patch-back detail
- edge conditions
Step 4 – Review Exterior Details (A2.2)
Exterior sidewalk detail provides:
- slab thickness
- edge preparation
- base requirements
These establish slab edge support requirements.
4. ESTIMATION PREPARATION STEPS
Before quantity takeoff, assumptions are defined:
Assumptions
- Existing slab is 4″ thick
- Thickened edges at slab repairs are 12″ wide x 12″ deep
- Plumbing trench repair averages 2′ wide
- Existing subgrade suitable for recompaction
- One mobilization only
Waste Factors
- Concrete: 10%
- WWF: 8%
- Dowels: 5%
These waste factors are higher due to small pours and cutting waste.
Labor Assumptions
Prevailing wage productivity assumptions:
- Slab demo: 15 SF/hr
- Subgrade prep: 50 SF/hr
- Concrete placement: 0.40 CY/hr
- Doweling: 8 EA/hr
Constructability Considerations
Small foundation repairs are costly because:
- Multiple isolated repairs reduce efficiency
- Doweling into existing slabs increases labor
- Small concrete placements incur mobilization inefficiencies
- Interior access constraints reduce production rates
These conditions substantially increase unit cost.
5. DETAILED MATERIAL TAKEOFF
A. Plumbing Trench Slab Restoration
Based on structural coordination:
Assume:
- 3 trench repairs
- 20 LF each
- 2′ wide
- 4″ slab thickness
Area:
3 × 20 × 2 = 120 SF
Volume:
120 × 4″/12 = 40 CF = 1.48 CY
Waste @10%:
1.48 × 1.10 = 1.63 CY
B. Thickened Slab Edge
Per trench perimeter:
- 3 trenches × 40 LF perimeter = 120 LF
Thickened edge:
- 12″ wide × 12″ deep
Volume:
120 × 1 × 1 = 120 CF = 4.44 CY
Waste @10%:
4.44 × 1.10 = 4.88 CY
C. Exterior Slab Repair
Assume:
- 60 SF slab repair
- 4″ thick
Volume:
60 × 4″/12 = 20 CF = 0.74 CY
Waste @10%:
0.74 × 1.10 = 0.81 CY
D. Total Concrete Volume
1.63 + 4.88 + 0.81 = 7.32 CY
Round to 8 CY
E. WWF Reinforcement
Total slab area:
120 + 60 = 180 SF
Waste @8%:
180 × 1.08 = 194 SF
F. Dowels
Assume:
- 120 LF perimeter ÷ 1.5′ spacing = 80 EA
Waste @5%:
80 × 1.05 = 84 EA
6. LABOR & PRICING BUILD-UP (Prevailing Wage)
Using Arkansas prevailing foundation labor rates:
Material Pricing
Concrete:
8 CY × $250 = $2,000
WWF:
194 SF × $2.25 = $437
Dowels / epoxy:
84 EA × $4.50 = $378
Vapor barrier / accessories:
Allowance = $425
Material Total:
$3,240
Labor Pricing
Slab Demo:
180 ÷ 15 = 12 hrs
12 × $72 = $864
Subgrade Prep:
180 ÷ 50 = 4 hrs
4 × $72 = $288
Concrete Placement:
8 ÷ 0.40 = 20 hrs
20 × $72 = $1,440
Doweling:
84 ÷ 8 = 10.5 hrs
10.5 × $72 = $756
Labor Total:
$3,348
Equipment
Saw cutting, mixer, tools:
$850
Direct Cost
$3,240 + $3,348 + $850 = $7,438
O&P
Overhead 10%
$744
Profit 10%
$818
Tax (8% material)
$259
Final Foundation Estimate:
$9,259
7. FINAL ESTIMATE SUMMARY
| Cost Item | Amount |
|---|---|
| Materials | $3,240 |
| Labor | $3,348 |
| Equipment | $850 |
| Tax | $259 |
| O&P | $1,562 |
| Final Estimate Total | $9,259 |
8. ESTIMATOR NOTES / PROFESSIONAL INSIGHTS
The foundation scope is small in volume but highly labor-driven, which is common for selective renovation foundation work.
The primary cost drivers are:
- Concrete mobilization for small pours
- Doweling into existing slabs
- Interior access restrictions
- Subgrade repair requirements
- Multiple isolated patch locations
Although only 8 CY of concrete is required, the installed cost is elevated due to:
- Small batch delivery charges
- Reduced labor efficiency
- Higher forming labor per cubic yard
- Tie-in complexity with existing foundations
Recommended bid clarifications:
- Unsuitable soils excluded
- Existing slab thickness assumed as shown
- Dewatering excluded
- No underpinning included
- One mobilization included
These clarifications reduce subcontractor risk exposure.