Roof Slab Waterproofing: Renewing a Failing Concrete Slab

Flat concrete roof slabs are common on homes and outbuildings across the greater Bloemfontein area, and they all share the same weakness: once the waterproofing membrane ages out, the slab has nowhere for water to go but in. This case study looks at a typical slab waterproofing job carried out using the ArmTec HyperFlex system, the same process BloemGuard follows on every slab renewal.

The problem

Flat roof slabs take a hard beating from the sun, and this one showed every year of it. The existing waterproofing membrane had delaminated and cracked, lifting away from the concrete substrate in sheets. Along the joints the old system had failed and started to separate, opening a direct path for water to sit and soak in.

Ponding was the clearest sign of trouble. Water was pooling on the slab instead of draining, because the outlet was no longer moving water off the roof correctly. UV protection on the old coating had long since burned away, leaving the membrane brittle and porous. Cracks had also opened up on the parapet wall, and around the drainage outlet the substrate had deteriorated badly, leaving a hollow, damaged section that had to be rebuilt before any new coating could go down.

The solution

As an approved SealPro applicator, BloemGuard installed the ArmTec waterproofing system to fully renew and reseal the slab. The work followed a proven sequence:

1. Open and correct the outlet. The drainage outlet was cleared and reworked so water flows off the slab correctly, eliminating the ponding at its source.
2. Prep and prime the substrate. The full slab surface was cleaned back to a sound base and primed with Penetrar to bond the new system to the concrete.
3. Reinforce the cracks and joints. Cracked and delaminated joints, along with the parapet wall, were strengthened and bridged with StretchSeal membrane to absorb movement.
4. Build the reinforced ArmTec membrane. HyperFlex was applied and embedded with ArmTec mesh across the slab, creating a tough, seamless, fully reinforced waterproofing layer.
5. Seal with the top coat. The system was finished with HydroSeal HF, a flexible, UV-stable topcoat that protects the membrane and keeps the slab watertight for years.

The result

The slab now carries a clean, unbroken waterproof membrane with proper fall to the corrected outlet, so water drains instead of pooling. The joints and parapet are reinforced, the damaged outlet area has been rebuilt, and the UV-stable finish means the homeowner will not be looking at cracked, flaking waterproofing again any time soon. What started as a tired, leaking roof slab becomes a durable, sealed surface ready to shrug off the next rainy season.

BloemGuard is an approved SealPro applicator serving Waterkloof and the greater Bloemfontein area.

Contact BloemGuard for a free inspection and quote: 072 933 0162 · bloemguard.co.za

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