The 2,744 sq. ft. footprint of this two-story custom home was used as the basis for the foundation cost comparisons in Table 1, and for calculating foundation + flood insurance costs in Table 3. The footprint includes the porches, but not the garage.
The 2,744 sq. ft. footprint of this two-story custom home was used as the basis for the foundation cost comparisons in Table 1, and for calculating foundation + flood insurance costs in Table 3. The footprint includes the porches, but not the garage.

A raised wood floor system is a cost-competitive alternative to a concrete slab system, especially in areas where the builder must meet a minimum “lowest floor elevation” at or above the Base Flood Elevation (BFE) required by local floodplain management ordinances.

As shown in Table 1, the cost of building a raised floor compares favorably to the cost of a slab. Table 1 summarizes the cost of just the foundation for four common system types — two raised floor options and two slab options. The spread between the four options is only $1,735, with the cost of the elevated concrete slab option (at +1 BFE) the most expensive at $14,751, and the monolithic concrete slab-on-grade (at BFE) the least expensive at $13,016. The two raised wood floor options (at +2 BFE) priced in between at $14,074 for the pier-and-beam and $13,723 for the stem wall system.

In addition to cost-competitive construction for the builder as shown, a raised floor can mean significant savings for homeowners in flood-prone areas. Table 2 and Table 3 show how homeowners can realize dramatic reductions in annual flood insurance premiums with a raised floor system. Furthermore, the initial investment in a raised floor more than pays for itself over a 30-year mortgage. For this example, the net result for choosing a pier-and-beam raised wood floor at +2 BFE instead of a concrete slab-on-grade (slab-on-ground) at BFE is an overall savings of $6,605 for the homeowner as shown in Table 3. Savings begin immediately and grow larger during the life of the mortgage as shown in Figure 1.

 

Table 1 Cost-Comparisons: Raised Floor vs. Slab
RAISED FLOOR OPTION — PIER-AND-BEAM FOUNDATION + 2 BFE
Item
Amount
Material
Labor
Unit Cost
Cost
Excavation Footings
10.9 CY
23.45
23.45
$
255
Termiticide Soil Treatment
333 SF
0.24
0.21
0.45
$
150
Footings Concrete
14.4 CY
92.00
39.78
131.78
$
1,899
#5 Rebar
296 LF
0.29
0.26
0.55
$
163
Foundation CMUs
500 Units
1.68
2.61
4.29
$
2,145
#5 Rebar
222 LF
0.29
0.26
0.55
$
122
Concrete
2.7 CY
92.00
39.78
131.78
$
354
Beams 6×6 PT
346 LF
3.08
0.60
3.68
$
1,273
Band Joists 2×12 PT
216 LF
1.70
0.55
2.25
$
486
Joists 2×12 PT
1910 LF
1.70
0.55
2.25
$
4,298
Anchor Straps 1-1/4×20 ga.
62 Each
0.89
0.89
$
55
Porch PT T&G Flooring
585 LF
0.41
0.20
0.61
$
359
Insulation R-19 Fiberglass
1920 SF
0.35
0.10
0.45
$
864
Subfloor 19/32 Sturd-I-Floor
1920 SF
0.57
0.29
0.86
$
1,651
Total Estimated Cost for Raised Floor Option — Pier-and-Beam
$
14,074
table1fig1
RAISED FLOOR OPTION — STEM WALL FOUNDATION + 2 BFE
Item
Amount
Material
Labor
Unit Cost
Cost
Excavation Footings
10.9 CY
23.45
23.45
$
255
Termiticide Soil Treatment
650 SF
0.24
0.21
0.45
$
293
Footings Concrete
7.3 CY
92.00
39.78
131.78
$
961
  #5 Rebar
442 LF
0.29
0.26
0.55
$
243
Foundation CMUs
734 Units
1.68
2.61
4.29
$
3,150
  #5 Rebar
311 LF
0.29
0.26
0.55
$
171
  Concrete
1.8 CY
92.00
39.78
131.78
$
242
Beams 6×6 PT
125 LF
3.08
0.60
3.68
$
460
Band Joists 2×12 PT
216 LF
1.70
0.55
2.25
$
486
Joists 2×12 PT
1910 LF
1.70
0.55
2.25
$
4,298
Still Plates 2×8 PT
221 LF
1.03
0.22
1.25
$
276
Anchor Bolts 1/2×6″
50 Each
0.28
0.28
$
14
Porch PT T&G Flooring
585 LF
0.41
0.20
0.61
$
359
Insulation R-19 Fiberglass
1920 SF
0.35
0.10
0.45
$
864
Subfloor 19/32 Sturd-I-Floor
1920 SF
0.57
0.29
0.86
$
1,651
Total Estimated Cost for Raised Floor Option — Stem Wall
$
13,723
SLAB OPTION — ELEVATED ON BACKFILLED PERIMETER WALL + 1 BFE
Item
Amount
Material
Labor
Unit Cost
Cost
Excavation Footings
10.9 CY
23.45
23.45
$
255
Termiticide Soil Treatment
2500 SF
0.24
0.21
0.45
$
1,125
Exterior Footings Concrete
7.3 CY
92.00
39.78
131.78
$
961
  #5 Rebar
442 LF
0.29
0.26
0.55
$
243
Foundation CMUs
734 Units
1.68
2.61
4.29
$
3,150
  #5 Rebar
311 LF
0.29
0.26
0.55
$
171
  Concrete
1.8 CY
92.00
39.78
131.78
$
242
Interior Footings Concrete
8.2 CY
92.00
39.78
131.78
$
1,076
  #5 Rebar
502 LF
0.29
0.26
0.55
$
276
Anchor Bolts 1/2×6″
50 Each
0.28
0.28
$
14
Fill Compacted Fill
156 CY
10.00
3.13
13.13
$
2,049
Slab Finish
2504 SF
0.42
0.42
$
1,052
  Concrete
30.6 CY
92.00
43.20
135.20
$
4,137
Total Estimated Cost for Slab Option — Elevated
$
14,751
table1fig2
SLAB OPTION — MONOLITHIC ON GRADE at BFE
Item
Amount
Material
Labor
Unit Cost
Cost
Excavation Footers
10.9 CY
23.45
23.45
$
255
Termiticide Soil Treatment
2500 SF
0.24
0.21
0.45
$
1,125
Exterior Footings Concrete
22.9 CY
92.00
39.78
131.78
$
3,020
#5 Rebar
442 LF
0.29
0.26
0.55
$
243
Interior Footings Concrete
8.2 CY
92.00
39.78
131.78
$
1,080
#5 Rebar
502 LF
0.29
0.26
0.55
$
276
Anchor Bolts 1/2×6″
50 Each
0.28
0.28
$
14
Fill Compacted Fill
82 CY
10.00
3.13
13.13
$
1,075
Formwork 2×8 Exterior
221 LF
0.90
1.59
2.49
$
550
2×4 Interior
95 LF
0.40
1.59
1.99
$
189
Slab Finish
2504 SF
0.42
0.42
$
1,052
Concrete
30.6 CY
92.00
43.20
135.20
$
4,137
Total Estimated Cost for Slab Option — Monolithic on Grade
$
13,016


Source: Estimate prepared by Thomas Stevens, III, Florida Certified Building Contractor, St. Pete Beach, Florida, using MEANS cost data, January 2003. Based on a 2,744 sq. ft. foundation footprint for a two-story house required to meet the strict Florida Building Code.
BFE = base flood elevation     CY = cubic yards     SF = square feet     LF = lineal feet     CMUs = concrete masonry units     PT = pressure treated     T&G = tongue & groove