Foundation Drainage
Why is drainage needed?
The answer is simple: waterproofing prevents water from damaging foundation materials, while drainage ensures the removal of that water. Therefore, waterproofing and drainage must be implemented together, but they cannot replace each other.
Drainage is a complex engineering system designed to remove excess moisture from foundation walls and the ground. This includes meltwater, rainwater, and groundwater. If a property is located in a depression or if groundwater levels are high, it's essential to implement measures to drain moisture from the site or at least from around the foundation. This helps prevent surface water accumulation and significantly reduces seasonal water level rise and stagnation.
A drainage system consists of pipes laid in a trench around the foundation perimeter, along with a manhole (inspection chamber). On the market, you'll find drainage pipes wrapped in geotextile. This prevents clogging and ensures long-term performance, extending the lifespan of the entire drainage system. However, keep in mind that using such pipes does not eliminate the need for geotextile within the system.
It's not just components that matter, but also proper system design. Only correctly prepared installations and properly executed work guarantee effective performance.
Types of Drainage
Two main types of drainage can be used to protect foundations from water: wall-attached (closely attached) and ring (perimeter) drainage. In the first case, one side of the trench is the foundation wall itself; in the second, the trench is located 1.5–3 meters away from the house. Use wall-attached drainage if the building has a basement or a ground floor level; ring drainage may suffice otherwise.
Ring drainage differs from wall-attached drainage in that it is located at a distance from the structure. Additionally, it features gentle pipe bends (curved joints), which is why it’s called 'ring'. The exact distance from the house doesn’t need to be precise, as long as it does not exceed 3 meters. However, one rule must always be followed: pipes must be laid below the foundation's sole.
Ring drainage is slightly less effective than wall-attached systems. It can be used when flooding is minimal and a concrete apron has been installed around the house. Note that wall-attached drainage is slightly more expensive than ring drainage, though not significantly so.
Installation Process
Installing a drainage system can take several weeks—likely not faster. Therefore, before starting work, protect the house’s perimeter from rain and debris. The following steps are involved:
Note: Sometimes wall-attached drainage is installed 0.5–1 meter away from the foundation. This preserves waterproofing integrity and ensures water runoff. However, in such cases, stormwater drainage cannot be installed.
Installing drainage is a costly process due to high labor intensity and material costs. However, it will only function properly if installed correctly—therefore, entrust the work to professionals and consider monitoring their performance.
