Steep slopes: how to protect your home against collapsing walls

Tonny Mutuwa, the projects manager at Qontrac Construction and Civil Engineering Limited, says one of the ways one can deal with the challenges that come with building on hilly or steep slopes, is by using embankment bricks on the upside where water and soil come from.

Here, Mutuwa says the bricks are laid in half, rectangle-like shape and when built on the sides of the compound holes are created in the wall, to allow rain water to flow out of the compound. Additionally, Isam Kambugu, a professional gardener, says this building style stops soil erosion during rainy seasons.

Unlike other styles of embankment, like the use of rocks, bricks and concrete cement among others, the soil and water keep flowing into the compound whenever it rains, and one needs to put up a good drainage system to help the situation. Kambugu says, with embankment bricks, water sinks into the soil and there is no gap left for any overflows.

Retaining walls like this at the bottom of the slope can help prevent water from running

The style gives room for flower gardening. Flowers usually make a good visual impression when planted in these holes. But one needs to ensure that they are not too close to each other.

“Plant a variety of species. Short flowering and running flowers are the best for this kind of gardening. This is because tall flowers cannot grow well in such a situation and might damage the embankment. Running flowers look good as they flow on top of these bricks,” Kambugu says.

For the embankment to remain firm for a reasonable period of time, it should not be built in a straight line. It should slant. Building on a hilly site requires more technical attention, and the more you get to know about it, the more it will help you make the right decisions.

Costs involved in building on a hilly site include the use of suspended concrete floors, beams, hard landscaping, extra work in stepping the foundation, retaining walls and drop manholes.

Cut and fill

Cutting away of soil from one place, and filling it in another to obtain desired levels is commonly done on sloping sites. This is one of the most economical ways of dealing with construction on steep levels. However, it calls for more work when you have to dispose of the soil away from site.

Plantable retaining walls can hold vegetables, herbs and flowers among others

Retaining walls

Fred Lukoda, a construction expert says retaining walls are built on site for purposes of holding back soil. These walls are expensive to construct, therefore, figuring out a simpler option of building a retaining wall will save you some costs.

Instead of building one high retaining wall, it is cheaper and visually more attractive to construct a series of lower retaining walls and the ground terraced between them. If it is well built, it also protects erosion depending on the planning. Another alternative is the wire cages (gabions) filled with stone or interlocking concrete blocks that are subsequently filled with soil and planted.

Level changes

The most cost-effective way of building on a sloping site is by having a split-level floor plan. However, this involves a series of stairs/steps between levels. Lukoda also says it should be noted that multiple floor levels do not appeal to the elderly, disabled or young people. However, on a positive note, change in floor level can be used as an informal way of defining different areas within an open plan space as an alternative of using partition walls.

The type of soil

Architect Abdu Wahab Nyanzi says some soils are loose while others contain ground water. These can cause buildings to collapse. He says the more time the graded slope remains bare, the greater the chances for the soil to be washed away. He says the type of building and the plan your engineer has should determine how the land is to be levelled, with terraces.

Nyanzi maintains that developers should know land is shaped differently, which is what an engineer or architect bases on to level the land.