# Basement Sealing # Contacts * [APS Waterproofing](https://aps-atlanta.com/) * 678-315-7761 * VFV7+G5 Smyrna, Georgia * 11 miles * Michael, texted 2026-08-25 08:47 * [All-American Waterproofing](https://www.all-americanwaterproofing.com/) * 404-301-3431 * MFMQ+M7 Atlanta, Georgia * 12 miles * bigger place with a call system * left a message 08:50 * scheduled meeting 2026-08-27 10a-12p * [Lifetime Basement Waterproofing](https://lifetimebasement.com/) * 770-607-3838 * QJQ7+5W Atlanta, Georgia * 15 miles * Tina * txt: 678-580-9694 --- # External Basement Waterproofing: Process & Checklist External basement waterproofing is the gold standard for below-grade water management. By excavating around the foundation and treating the exterior face of the walls, this method stops water **before** it touches the concrete structure and relieves hydrostatic pressure at the perimeter. --- ## Part 1: Excavation & Waterproofing Process ### Step 1: Site Preparation & Trench Excavation * **Excavation Depth:** Heavy machinery or hand tools excavate a trench around the foundation perimeter down to the top (and outer edge) of the concrete footing. * **Safety & Bench/Shoring:** Depending on soil stability and depth, trenches must be sloped back, benched, or shored with trench shields to prevent soil collapse during installation. * **Utility Clearance:** All underground lines (gas, power, water, fiber) are located, marked, and carefully hand-dug around near the foundation. ### Step 2: Wall Cleaning & Substrate Surface Prep * **High-Pressure Cleaning:** The exposed foundation wall is pressure washed to remove dirt, loose mortar, clay residue, and old degraded coatings. * **Structural Crack & Joint Repair:** Cracks, honeycombing in poured concrete, or degraded mortar joints in masonry blocks are excavated and filled with non-shrink hydraulic cement or structural epoxy mortar. * **Parging (Masonry/Rough Concrete):** A fresh parge coat (smooth cementitious mortar layer) is applied to block or rough walls to ensure a continuous, flat substrate. * **Footing Cove (Fillet):** A 45-degree concrete fillet or cove is constructed at the right-angle joint where the wall meets the top of the footing. This prevents water from pooling in the sharp corner. ### Step 3: Primary Waterproofing Membrane Layer > **Note:** Asphalt "damp-proofing" coating (black foundation paint) is *not* waterproofing. Waterproofing materials must span hairline cracks and withstand continuous hydrostatic pressure. * **Membrane Material:** Thick rubberized asphalt, elastomeric liquid membrane, or cold-applied self-adhering modified bitumen sheets are applied to the primed wall. * **Coverage:** The barrier spans from below the top edge of the footing up to finished ground level grade line. * **Reinforcement:** Critical stress points, structural cracks, and wall-to-footing transitions are reinforced with embedded synthetic fabric or fiberglass mesh. ### Step 4: Protection & Vertical Drainage Board (Dimple Mat) * **High-Density Polyethylene (HDPE) Mat:** A heavy dimpled drainage board is mechanically fastened over the rubber waterproofing membrane (dimples facing toward the wall). * **Dual Protection:** 1. **Mechanical Protection:** Shields the delicate liquid/sheet membrane from sharp rocks during backfilling. 2. **Drainage Channel:** Creates an uninterrupted vertical air gap so any surface water immediately drops straight down to the footing pipe. * **Termination Strip:** Heavy plastic or metal flashing is sealed to the top edge above ground level to prevent dirt and surface runoff from slipping behind the dimple mat. ### Step 5: Footing Drain Tile & Filtration Matrix * **Drain Pipe Selection:** Smooth-bore perforated rigid PVC (ASTM D3034 or Schedule 40) is preferred over flexible corrugated black pipe because it resists crushing and maintains pitch. * **Slope & Layout:** The pipe sits along the outer edge of the footing (sloped at a minimum 1/8 inch per foot) toward a gravity outlet or internal/external sump basin. * **Washed Aggregate:** 12 to 18 inches of clean, washed aggregate (e.g., #57 crushed stone) completely encapsulates the perforated pipe. * **Geotextile Filter Fabric:** Heavy needle-punched non-woven filter fabric wraps the gravel envelope to prevent silt and soil fines from clogging the drain line. ### Step 6: Backfilling, Compaction & Grading * **Layered Backfilling:** Backfill soil is replaced in 8- to 12-inch lifts and compacted to minimize future settling. * **Positive Pitch:** The final topsoil is sloped away from the foundation wall at a minimum grade of 6 inches over the first 10 feet. * **Surface Water Management:** Roof downspouts and yard runoff are piped completely outside the excavation footprint to avoid re-saturating the backfilled zone. --- ## Part 2: Essential Questions to Ask Your Waterproofing Contractor | Category | Questions to Ask | What to Look For | | :--- | :--- | :--- | | **Materials & Specs** | • What exact membrane product will be applied to the wall?
• Are you using dimple board over the rubber coat?
• What type of pipe are you installing for the footing drain? | • Liquid elastomeric rubber / thick bitumen sheet (not spray asphalt).
• High-density dimpled sheet mat (HDPE) with top termination strip.
• Rigid, smooth-bore perforated PVC pipe with cleanouts. | | **Site Prep & Safety** | • How will landscaping, decks, and hardscapes be protected?
• What shoring or benching measures will be used for trench safety?
• How do you handle unexpected rock outcroppings or high groundwater? | • Clear site preservation plan & utility locates.
• Compliance with OSHA trench safety standards.
• Written contingency protocols for subsurface obstructions. | | **Drainage System** | • Where does the new perimeter pipe discharge?
• Are accessible cleanout ports installed at corners?
• Is the gravel bed wrapped in geotextile fabric? | • Gravity daylight discharge, dry well, or dedicated sump system.
• Vertical PVC cleanouts extended above grade for future jetting.
• High-quality non-woven geotextile envelope. | | **Warranty & Credentials**| • Does your warranty cover both labor and materials?
• Is the warranty transferable to future homeowners?
• Are you licensed, bonded, and carrying General Liability + Workers' Comp? | • Comprehensive multi-year or lifetime transferable warranty.
• Written warranty terms (avoid verbal guarantees).
• Active contractor license & valid certificates of insurance. |