When basements leak, it's easy to assume it's a fault with the membrane install. But industry data tells a different story.
90% of basement waterproofing failures are caused by poor concrete compaction- not defective products.
Even the most carefully considered waterproofing design ultimately depends on what happens during concrete placement and compaction on site. Despite advances in mix design, additives, and detailing, the quality of the final structure is heavily influenced by the operatives on the ground.
Sometimes, we question whether site personnel fully appreciate that their workmanship directly impacts not only the concrete finish but also the waterproofing integrity of the structure. Voids, segregation, honeycombing or cold joints - often the result of poor placement or inadequate compaction - can compromise the concrete's ability to act as a watertight barrier.
It's a timely reminder that waterproof concrete is not just about materials or design- it's about execution. Without diligence and proper training on site, even the best-laid plans can literally leak.
Insufficiently compacted concrete leads to:
For type B integral protection systems, which rely on watertight concrete, poor compaction undermines the entire strategy. The issue isn't the design. It's the execution.
Certain locations are especially vulnerable:
These are weak spots that often come back to haunt projects.
Compaction failures are invisible until leaks appear. By then, the cost is huge:
Prevention always costs less than repair.
To minimise risk:
Even the best waterproofing spec can't compensate for poor site practice.
Erect the Formwork
Erect the wall formwork/shuttering ready for the concrete pour. Ensure shuttering panels, soldiers, ties and supports are clean, straight and are free of damage. Make sure the base slab or footing is clean and level for accurate alignment.
Slump Test On Arrival
Every time a concrete wagon arrives, carry out a slump test before you start pouring. This ensures t he concrete has the right consistency. If you're unsure, call the technician. Never add water to the concrete on site.
Take Cube Samples
Take cube samples as required for testing the concrete's strength later on. Make sure the correct procedure is followed when collecting samples.
Turn On Vibrating Pokers
Once the concrete mix is correct, drop 4 no. 65mm pokers evenly along the left of the 6 metre wall pour. Before any concrete goes into the wall, make sure all pokers are turned on and working. Pokers help remove air and compact the concrete properly.
Pour the First Concrete Layer
Pour 2 skips of concrete into the wall - each skip holds 0.7m³ so together that’s 1.4m³. This amount will fill the wall to around 750mm high. Do not move the pokers during this first layer until the bubbles stop rising, the concrete settles and the pitch of the vibrator changes.
5-15 seconds is a guide but visual control is critical.
Raise the Pokers
Once the first layer is poured, raise the pokers up by 700mm. The tip of each poker should still sit 50mm inside the top of the wet concrete. This keeps the compaction consistent between layers. Avoid repeatedly lifting and dropping the pokers, as this may introduce additional air bubbles into the concrete.
Use Pencil Pokers or Formwork Vibrators
After each layer is poured and the main pokers are in position, use a pencil poker to remove any trapped air bubbles. Focus especially around edges and tight areas where the bigger pokers might not reach. Once the pokers are inserted avoid repeatedly lifting and dropping them as this may introduce additional air bubbles into the concrete. The use of a formwork vibrator can also be used particularly for thin, heavily reinforced or inaccessible walls where pokers cannot reach.
Repeat for Each Layer
Keep repeating the process:
Pour 2 skips (1.4m³)
Raise the pokers 700mm (keeping them in the top 50mm), and use the pencil poker as before.
You'll pour 5 layers in total, each about 750mm high.
Remove the pokers once the fifth layer has been poured.
Complete the Wall
After 5 layers, the wall will be around 3.75 to 4 metres high. This will use a total of 10 skips of concrete.
Check the surface finish and make any final adjustments.
In Summary
At a glance, based on a 6m wide by 4m high wall:
1. Set up 4 pokers across the concrete pour width.
2. Pokers must be turned on before the first concrete pour, then raised after each pour, leaving 50mm of the poker in the curing concrete prior to the next pour.
3. This process is repeated after each pour, until the 5 pours are complete. Avoid repeatedly lifting and dropping the pokers to avoid additional air bubbles occurring within the concrete.
4. Use pencil pokers and/or formwork vibrators during each pour to remove air bubbles in areas not accessible by larger pokers.
At Premcrete, we design systems with construction realities in mind:
We also advise early on mix design, pour sequencing, and high-risk areas - preventing issues before they happen.
Waterproofing design isn't standalone. It must align with construction methods. That means:
The takeaway is clear: membranes alone won't save a project. Success depends on concrete compaction - the hidden 90% factor.
By combining smart design, robust detailing and proven site practice, long-term watertight performance is achievable.
Speak to Premcrete about integrated waterproofing solutions and compaction best practice: projects@premcrete.com