Do puddles remain on the lawn or terrace after a heavy rain shower? Or is your garden moist all year round? Then drainage is the solution. Too wet is not only annoying for your own garden pleasure, it is also not conducive to trees, shrubs and plants.
Where does the flooding come from?
If the rainwater does not sink into the ground, but remains in places in your garden, this can have various causes. The soil type plays a role. Clay is less water permeable than sandy soil. The groundwater level may be high locally or the ground may have settled. This is often the case with new construction, because the construction activities have affected the soil structure. But also in places where you walk a lot, the ground can become so firm that water does not pass easily.
Here’s how you make a drainage system
- Flat shovel
- Measuring tape
- Stanley knife
- Drainage pipe
- Gravel, shells or coarse sand
Drainage of your garden can be done in various ways. In places that always stay wet, you can dig sinks, deep holes that you fill with gravel. But the most thorough and structural solution to the problem is the construction of a drainage system with perforated drainage pipes. Here we explain how to tackle this labor-intensive, but rewarding job.
To start with the bad news, you will have to spit heavily in your hands and dig 20cm wide slots for the drainage pipes throughout the garden. The depth depends on the groundwater level: the pipes must be above that. If the groundwater is not a problem, the slots should be at least 60 cm deep. The recommended distance between the slots is 5 to 6 meters, so that no spot in the garden is more than 3 meters from a drainage pipe.
Lay the drainage pipes
Different types and sizes of drainage pipe are available. The type commonly used for gardens consists of flexible PVC pipes with thousands of small holes. The tubes are wrapped with coconut or synthetic material to prevent soil from clogging the holes. The usual pipe diameter for gardens is 80mm.
You lay the tubes horizontally on a bed of at least 3cm of gravel, coarse sand or shells. You can easily cut them to size with a Stanley knife. Next you fill the trenches with gravel, sand or shells up to 20cm below ground level, after which you level the garden again with the scooped soil.
It will take a while before your garden is presentable again, but you have solved the flooding once and for all, and from now on the drainage system will work invisibly.
Drainage under the terrace
Even if no rainwater remains on the tiles, drainage under the terrace is important. If the soil underneath remains wet, you run the risk of the tiles being pushed up in frost. Special gutters are available for terraces and other garden paving, which can be placed along the edges or between the stones and connected to the drainage pipes.
Tip: A terrace on which you will never suffer from wet feet is a wooden deck that rests on beams or picket posts above the ground. You can read how to make such a wooden terrace in Making a wooden deck.