How we Permanently Waterproofed a leaking masonry Pool in Karen, Nairobi.

Introduction

If you look at our portfolio, we have repaired a lot of swimming pools in the past. From below ground swimming pools to suspended swimming pools. But what makes waterproofing an art is that every swimming pool we have repaired  has had different approaches job. This is because site conditions and requirements vary from project to project. This is the reason why I always advocate for waterproofing professionals for each project

In this case, we handled a very interesting swimming pool because of the history it had. The pool had been previously repaired 4 times but it was still leaking. 4 times!!!. So when the owners called us for help, they were really drawing their last straw.

Problems and Challenges

• The owners did not have the history of the swimming pool. There was no information on whether it was concrete or masonry; there was no information on the thickness of the slab. No info on the class of concrete used and reinforcement used. No structural drawing of the pool. (Historical data of any structure is very vital as it guides on the approaches to be taken when waterproofing)
• The swimming pool already had finishes. It is very hard to diagnose a swimming pool with finishes.
• After we removed the finishes, we discovered the pool had a thick screed of over 4 inches thick. (I always find this phenomena common with contractors. Putting a very thick plaster or screed does not waterproof a pool. Or a tank)
• After removing the screed, we discovered a crack running across the slab.
• The masonry stones used on the walls were the porous type.

Notice the leakage coming from the slab

Removing terrazzo, plaster and screed

Removal of terrazzo, plaster and screed

Exposed reinforcement on the walls

The Solution

Together with the Structural Engineer, the contractor and our team, we decided to double waterproof the pool. This meant using to materials to waterproof the pool, namely Penetron Admix, Penecrete mortar and Duraflex cementitious membrane. And on top of that we decided to cast a new concrete slab (with Penetron Admix) on top of the existing one.

We decided to take this cautious approach because no historical data was present. In such situations, I always take the approach of worst case scenario.

The following were the steps taken:

• Surface preparations: We repaired the crack that was at the floor slab and also removed the existing plaster to expose the stones
• Concreting the floor slab: We concreted a new floor slab, 150mm thick, class 30. The concrete was mixed with Penetron Admix
• We plastered the walls using concrete (using the small 3/16 ballast). The concrete was  mixed with Penetron Admix. A layer of plaster, mixed with Penetron Admix, was added so as to receive Duraflex Waterproofing membrane.
• Duraflex application: We lined the walls and the floor slab with Duraflex Waterproofing membrane. It was reinforced with Ecofelt reinforcement mesh. After it was cured, a layer of plaster and screed was laid to receive finishes.
• Finishes: The finishes were laid.

Casting the concrete slab. The concrete was mixed with penetron admix

Vibrating the poured concrete

Casted concrete slab

Applying Duraflex cementitious membrane

Duraflex is a ready to use flexible slurry based on a special synthetic resin dispersion and a blend of selected cements mixed with carefully graded aggregate

Duraflex is used for :
-Protection and repair of balconies, terraces and haunching concrete of roads and bridges.
-Waterproofing of new and old buildings (internal and external)
-Waterproofing of tanks, containers and water reservoirs.

Duraflex application on a plastered surface

Duraflex can be applied by a brush or a roller

We used Ecofelt reinforcement mesh

Ecofelt reinforcement mesh cut into strips

Pool lined with duraflex and reinforced with ecofelt reinforcement mesh

The pool was tested and it was watertight. Next, tiles were laid and the pool was ready for use

Tiles were laid and the pool filled with water

Tiles were laid and the pool filled with water

The team

• Waterproofing Applicator: Mau West Co. Ltd
• Structural Engineer: Engplan Consulting Engineers
• Contractor: Mukanzi Developers

Materials Used

• Penetron Admix- crystalline admixture in powder form that is added to new concrete during batching. It is also added to mortar for plastering
• Penecrete mortar- Used in combination with PENETRON for filling non-moving cracks and construction joints, form-tie holes, honey-combed areas and structurally damaged concrete. We used it to fill the voids around the lights and pipes
• Duraflex-  Two component, polymer modified, cementitious coating.
• Sand, cement and course aggregates for Concrete (class 30),  plaster and screed.
• Tiles

Project Duration

8 weeks