This was a PU injection waterproofing job in Kempas, Johor Bahru, involving water seepage through a concrete ceiling. Before starting the injection work, I first looked at the affected areas and planned the injection points based on where the water appeared to be travelling through the concrete.
The objective was not simply to stop the visible dripping point. Water can travel within cracks, joints and voids in concrete before appearing at the ceiling below, so the injection points had to be positioned around the affected area to intercept the water path.
This repair was carried out by VROOF as part of our waterproofing and leakage repair work in Johor Bahru.
The Leakage Condition
The visible leakage was appearing along the concrete ceiling and near the wall junction. Several points showed signs of water movement, but the place where water becomes visible is not always the exact point where it first enters the concrete.
For this reason, I treated the affected section as a water path rather than focusing on only one visible wet spot.
Preparing the Work Area
Before injection started, the surrounding area was protected because PU resin can expand and escape through nearby cracks or joints during the injection process.
The injection points were then drilled into the affected concrete section and fitted with injection packers. Their positions were arranged along the suspected water path so the resin could be introduced into the cracks and voids within the concrete.
PU resin was injected through the installed packers into the affected concrete. When the material encounters moisture, it reacts and expands, helping to fill cracks and voids that may be allowing water to travel through the slab.
During injection, the response at nearby points was observed carefully. Resin appearing from an adjacent crack or injection point can also provide useful information about how the internal water path is connected.
Working Around the Ceiling
Access is also an important part of PU injection work. In some areas, the concrete surface can be reached directly, while other sections may be hidden above a plaster ceiling.
Where access was available, the injection work was carried out through the ceiling opening so the affected concrete could be treated directly. This is why the ceiling condition and available access should always be checked before confirming the repair method.
What I Learned
PU injection can be an effective method for treating water seepage through concrete, but the injection itself is only one part of the repair.
Understanding where the water is travelling, selecting suitable injection points and having proper access to the concrete are equally important. A visible dripping point does not always tell the full story of where the water entered or how it travelled through the structure.
For me, the most important part is still the investigation: identify the likely water path first, then choose the repair method based on what we find.