19/08/2025
Why Damp Proof Membranes Don’t Belong Under Footings or Underground Beams
At Liannet Contractors U LTD, we don’t just build, we build smart.
The image above highlights a common but critical error: placing a damp proof membrane (DPM) directly beneath structural footings and underground beams.
Here’s why this practice is not advisable:
🔹 Compromised Load Transfer
Concrete footings are designed to transfer structural loads directly into the subsoil. A DPM introduces a slippery, non-structural layer that can reduce friction and compromise stability especially under dynamic or uneven loads.
🔹 Risk of Settlement and Shear Failure
When the membrane is placed under footings, it can act as a slip plane, increasing the risk of differential settlement or shear failure over time. This undermines the long-term integrity of the structure.
🔹 Moisture Management Misunderstood
DPMs are meant to block moisture from rising into habitable spaces—not to sit under load-bearing elements. Proper moisture control in foundations should involve well-designed drainage, hardcore layers, and blinding, not plastic sheeting beneath structural concrete.
🔹 Code Compliance and Engineering Standards
Most structural codes and engineering guidelines discourage or prohibit placing DPMs under footings. Instead, membranes should be positioned above the footing and below the slab, where they serve their intended purpose without interfering with structural performance.
At Liannet, we prioritize durability, safety, and compliance. Every beam, footing, and membrane we place is guided by engineering logic not shortcuts.
đź“Ś Build it once. Build it right.
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