Building a CMU house on a monolithic slab in Florida.

Florida (FBC 7th Ed./IRC 2021) requires a two-pronged approach: Soil Treatment + Physical Barrier.

1. Soil Treatment (Chemical) — Mandatory

• Code: FBC R318.1 / IRC R318.1; Florida Statute Ch. 482 (regulates application).
• Action: Must be applied by a licensed pest control operator (PCO). You cannot buy/apply termiticides yourself in FL.
• Timing: Treat after final grading but before vapor barrier/slab pour.
• Scope: Treat entire slab area, perimeter trench (min. 6" deep x 6" wide), around all pipe penetrations, and CMU block cores at grade.
• Documentation: PCO must provide Form HRS 1838 (Termite Treatment Certificate) to the building department for final CO.

2. Physical Barrier — Mandatory (FBC R318.2 / IRC R318.2)

You need one approved method at all slab penetrations and perimeter:

• Stainless Steel Mesh (e.g., Termimesh, Polyguard): Install at all pipe penetrations, cold joints, and perimeter edge. Mesh must be clamped/bonded to pipes.
• Sand Barrier (16/30 mesh): 4" minimum thick layer under entire slab and 12" out from foundation. Rarely used in FL due to sand availability/cost.
• Crushed Stone (Termite Shield): Not a standalone barrier per code; usually supplemental.
• Slab Edge Exposure: Maintain 6" minimum between final grade and top of slab/sill plate (FBC R317.1 / IRC R317.1) for inspection.

3. CMU Specifics (Monolithic Slab)

• First Course: Lay first course of CMU in full mortar bed on slab (no gaps).
• Bond Beam: Solid grout bond beam at top of wall (hurricane code) — also caps termite entry.
• Penetrations: Seal all utility penetrations (plumbing, electric, HVAC) through slab and CMU with non-shrink grout, epoxy, or approved sealant before backfill. Mesh collars required at pipes.
• Through-Wall Flashing: Install at base of veneer/weep screed per FBC R703.8.

4. "Monolithic" Clarification

True monolithic pour (slab + footing + grade beam = one pour) eliminates the cold joint at the footing. You still must treat soil under the entire slab area and install physical barriers at every penetration.

Critical Path

1. Rough grade → 2. PCO treats soil → 3. Install vapor barrier (Stego 15mil+) + mesh at penetrations → 4. Place rebar/chairs → 5. Pour slab → 6. PCO treats perimeter trench after forms pulled → 7. Lay CMU.

**Do

For a CMU (concrete masonry unit) house on a monolithic slab in Florida, termite protection is critical due to the state’s high subterranean termite pressure (especially Coptotermes formosanus and Reticulitermes spp.). Florida Building Code (FBC) and the International Residential Code (IRC), as adopted by Florida, require specific termite-resistant measures.

Required Actions:

1. Soil Pretreatment (Termiticide Application): - Apply a liquid termiticide to the soil beneath and around the slab perimeter before pouring concrete, per FBC R318.4 and IRC R318. - Use EPA-registered products (e.g., bifenthrin, fipronil, imidacloprid) at label rates. - Treat the soil to a depth of at least 6 inches and extend 12–18 inches outward from the foundation edge. - Note: This must be done by a licensed pest control operator in Florida (Chapter 482, F.S.).

1. Physical Barriers (Optional but Recommended): - Install a stainless steel mesh termite barrier (e.g., Termimesh®) or plastic sheeting (6-mil poly) under the slab if not using soil treatment alone. - For monolithic slabs, a vapor barrier (6-mil poly) is required under the slab per FBC R506.2.3 — this can double as a physical termite barrier if sealed properly at penetrations.

1. Slab Penetrations & Joints: - Seal all slab penetrations (plumbing, electrical, conduits) with termite-resistant sealant (e.g., polyurethane or silicone-based) to prevent termite entry. - Leave a minimum 2-inch inspection gap between the bottom of any wood framing (e.g., sill plate) and the slab — but note: on a monolithic slab, CMU walls typically sit directly on the slab. - Critical: Use pressure-treated or naturally decay-resistant wood for any wood in contact with or near the slab (e.g., door bucks, nailers). FBC R317.1 requires pressure-treated wood for sill plates in termite zones.

1. CMU-Specific Considerations: - Grout and reinforce CMU walls per FBC R606.2.1 — solid grout cores reduce termite harborage. - Ensure the top of the CMU wall is capped with a moisture-resistant barrier (e.g., metal flashing or membrane) to prevent wicking and termite access from above.

1. Inspection & Maintenance: - Schedule annual termite inspections by a licensed pro. - Keep mulch, soil, and vegetation ≥12 inches from the slab edge. - Avoid direct wood-to-soil contact anywhere on the property.

Bottom Line: Soil pretreatment by a licensed applicator is mandatory under FBC for new construction in Florida. Do not rely solely on the slab — termites will exploit cracks or joints. Combine chemical treatment, proper detailing, and vigilant maintenance. *Always consult your