Conventional Drainage
A System That Discharges Rainwater by Natural Fall and Gravity.
Conventional drainage is the traditional solution that safely carries rainwater away from roofs, terraces, balconies and outdoor areas by gravity, through outlets, gutters, downpipes and horizontal pipes.
Request a Quote for Your Project →Conventional drainage discharges rainwater by fall and gravity.
The system consists of roof outlets, gutters, downpipes, horizontal collector pipes, manholes and external discharge connections.
Conventional rainwater drainage is the most widely used roof drainage system. The fall of the roof surface directs water to outlets or gutters, from where downpipes carry it to ground level or to the rainwater drain.
It is a practical, economical and easy-to-maintain solution for residential buildings, small and medium-sized commercial buildings, balconies, terraces, car park ramps and traditional roofs.
Which details matter in conventional drainage?
The roof area, fall, number of outlets, pipe diameter, downpipe positions and external discharge directly affect system performance.
Roof Outlets and Collection Points
Roof outlets are the first point at which rainwater passes from the roof surface into the drainage pipework. On flat roofs, terraces and balconies, the position and level of outlets must be planned carefully to prevent ponding.
If too few outlets are provided, water can pond on the roof during heavy rainfall. This creates risks such as damage to waterproofing, overflowing parapets, ceiling leaks and additional structural loads.
Technical installation details
| Function | To take rainwater from the roof surface into the drainage pipework |
|---|---|
| Suitable applications | Flat roofs, terraces, balconies, car park decks, plant roof areas |
| Points to note | Outlet level, waterproofing detail, leaf guard, overflow line, maintenance access |
Rainwater Downpipes
Downpipes carry rainwater collected on the roof vertically down to ground level or to the external rainwater drain. The pipe diameter must be selected according to the roof area and the volume of water to be discharged.
Downpipes may be exposed on the façade or routed through a shaft inside the building. For internal pipes, condensation, noise, maintenance access and tightness must also be considered.
Technical installation details
| Typical diameters | Ø75, Ø90, Ø100, Ø110 mm; Ø125 / Ø160 mm depending on the project |
|---|---|
| Pipes used | PVC, PP, HDPE, steel, aluminium or gutter and downpipe profiles according to the system |
| Risks | Insufficient diameter, frost, staining on the façade, blockages, leaking joints |
Gutters and Horizontal Collector Pipes
On pitched roofs, rainwater is usually collected by gutters and carried to the downpipes. The gutter cross-section must be selected according to the roof surface, rainfall and spacing of the downpipes.
An insufficient gutter cross-section, incorrect fall or too few downpipes can cause overflowing, staining of the façade, water collecting around the foundations and damage to waterproofing.
Technical installation details
| Suitable applications | Pitched roofs, houses, small commercial buildings, garage and warehouse roofs |
|---|---|
| Material options | PVC, galvanised steel, aluminium, zinc, copper and coated metal gutter systems |
| Points to note | Gutter fall, downpipe spacing, leaf guards, snow load, façade connections |
External Rainwater Discharge
Rainwater from the roof must be connected to a safe discharge line at ground level. This can lead to the municipal storm drain, a soakaway, a rainwater storage tank or controlled surface drainage.
If downpipes discharge directly around the building’s foundations, damp in the basement, water collecting around the foundations, frost damage and surface deterioration can occur. External discharge is therefore an important part of the system.
Technical installation details
| Main drain diameters | Ø110, Ø125, Ø160, Ø200 mm and larger diameters as required by the project |
|---|---|
| Discharge point | Storm drain, manhole, soakaway, storage tank or controlled surface discharge |
| Points to note | Levels, fall, frost depth, traffic loads, manhole access, risk of backflow |
What should you consider when choosing a conventional drainage system?
1. The number of outlets and downpipes must be calculated correctly.
If too few downpipes are provided for the roof area, overflowing and ponding can occur during heavy rainfall.
2. Falls and levels must be correct.
Incorrect falls on roofs, gutters, terraces and external pipes can cause standing water or backflow.
3. Maintenance access must be provided.
Outlets, gutters, downpipes, manholes and access covers must be accessible for regular cleaning.
4. Water must not be discharged uncontrolled around the foundations.
Rainwater must be carried away from the building’s foundations and connected to a suitable drainage or rainwater line.
Let’s plan the right conventional drainage system for your roof and outdoor areas.
We will prepare a safe rainwater solution based on the roof area, gutter size, number of downpipes, outlet capacity and external discharge.