PART C · Site preparation and moisture
Damp proof courses and membranes explained
A damp proof course usually interrupts moisture movement through a wall. A damp proof membrane commonly protects a floor from ground moisture. They serve related purposes, but installing one does not automatically provide the protection needed from the other.
Why do the connections matter
Part C concerns the performance of the completed construction. Wall and floor protection need appropriate continuity, especially at corners, thresholds and junctions with existing buildings.
Ask for a detail showing how the floor membrane connects to the wall protection. A note saying that both are provided leaves the important junction unexplained.
What is a bridge
A bridge is a route around the intended moisture barrier. Raised paving, mortar debris or an unsuitable connection can allow moisture to bypass protection. The precise risk depends on the form of construction.
Keep external levels, drainage and wall details coordinated. A flush doorway may need a carefully designed threshold rather than simply raising the paving to match the internal floor.
Will a new damp proof course cure a damp wall
Not necessarily. Leaking gutters, defective pointing, plumbing leaks and condensation need different remedies. Establish the moisture source before paying for an injected treatment or extensive replastering.
For an extension, consider how the new wall and floor meet the original house. Older construction may not behave like a modern cavity wall.
What should be checked on site
Inspect membrane condition, laps, penetrations and specified connections before concrete or finishes hide them. Check that service pipes do not leave an unintended gap through the barrier.
Keep photographs and the agreed details, but arrange the required inspections as well. Good records can help diagnose a later defect; they do not make a poorly executed junction perform properly.
Where ground gases are present, the membrane specification and detailing may need to address those risks as well as moisture.