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Hollow Core Concrete Slab Water Leak Repair

Hollow Core Concrete Slab Injection

What is a Hollow Core Slab ?

A hollow core concrete slab, also known as a hollow core slab, is a precast slab of prestressed concrete, typically used in the construction of floors in multi-story buildings and parking structures

Parking Garage Repair with SealBoss 1510 Foam Injection

The Problem

The client was experiencing water intrusion through hollow core concrete slabs and along exterior wall and sill plate cold joints in below parking garage causing water to drip onto cars and creating unsightly watermarks on the walls.

A waterproofing contractor was asked to seal the cold joints and cracks in the affected hollow core concrete slabs, and to determine and stop the source of leakage.

The Solution

To address the issue of the leaking hollow core slab, the contractor reached out to the SealBoss Regional Sales Manager to advise on the injection of the hollow core slab.

With a quick walk around the exterior, it was made clear that there were drainage issues where the downspouts fed the run-off onto a grassy area with no sloping to direct the water away from the building.

Once the source of the leak had been determined, a two-step injection strategy was adopted as the best solution. The initial injection was to inject cracks in the hollow core slab where water was leaking out and dripping onto vehicles. The subsequent injection would be to seal off the end caps of the hollow core cells where the leak originated.

Once the contractor began to drill holes for the injection packers, water poured out and it was obvious that the hollow core was completely filled with water. After the water was drained the crack was injected and sealed.

To verify that water had not traveled between cells, weep holes were drilled into the adjacent cells. Water was found to have also filled another cell of the hollow core and had to be drained.

Using a borescope, it was confirmed that there was water intrusion where the hollow core had been capped off with a plastic cap (see video below).

The weep holes were left open to prove that the leak had subsided.

The client was advised to add drainage boxes to help direct flow away from the building in areas where water pooled and to notify contractor of any new leaks this upcoming spring when the ground will thaw.

SealBoss 1510 NSF/ANSI 61 Water Stop Foam was injected into the exterior cold joint along the areas where water intrusion was visible from efflorescence or rust stains. All visible leaks were addressed using the 1, 2, 3, 45 Degree method via injection packers that were placed roughly 12” from the joint where ½” holes were drilled at a 45-degree angle back into the joint. 1510 was injected until positive refusal of the hydro-active resin was visible along the cold joint.

All affected cells of the hollow core concrete slabs were injected approximately 6” from the end cap and sealed off using SealBoss 1510 NSF/ANSI 61 Water Stop Injection Foam System.

Products Used:

Injection Resin: SealBoss 1510 Hydrophobic Water Stop / Leak-Seal Foam w/ 15x Accelerator

Injection Packers: SealBoss 1/2” 13-100 Evolution Aluminum Packers

High Pressure Pump: SealBoss P2002 Single Component Injection Pump

Cleaning Materials: R70 Pump Flush, Xylene, rags, bucket

Additional Tools: 18” x 1/2″ drill bit — 3/8” Crescent Wrench — Dead Blow Hammer
Hammer Drill — Access 110v Power — Vacuum

SealBoss ® 1510 NSF Hollow Core Slab Water Stop Foam:

  • Hollow Core Slab Leak-Seal Repair, Crack & Joint Leak Sealer

SealBoss ® 1510 Hollow Core Concrete Slab Seal Foam Advantages:

  • Low Viscosity
  • Fast Cure Time
  • Advanced and Proven SealBoss ® Product-Pump-Packer System


Bestselling SealBoss ® Brand P2002 Injection Pump Advantages

  • Light Weight Injection Pump
  • High Quality Components for Durability
  • Proven Design – Thousands of Units Sold
  • Easy To Clean
  • Easy To Maintain
  • Heavy Duty For Daily Use
  • Pressure Gauge, Hose Set, Hopper Included
  • Recommended For Beginners & Injection Pros
  • > 5000 PSI Injection Pressure Possible

In Person and Video training is available upon request, contact SealBoss today to speak to your regional technical representative on our SealBoss full system solutions and offerings. 

 “While providing jobsite assistance, support and training, we create a positive learning environment where confidence and a level of comfort can be achieved in a short period of time allowing for successful repairs to be continued after the training.

From training new companies to new employees, SealBoss has continued to provide support to our users for 36 years.

With a knowledgeable technical support team, we are here to help with any questions you may have”

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