Although building on a hill may be a challenge, the property market has opened up a lot of hilly areas for construction now days.
Abdu-Wahab Nyanzi, an architect, says much as building on a slopping site is more of a technical issue, hilly areas bring special challenges to the experts in a number of ways.
“Concrete floors, hard landscaping, stepping the foundation, retaining walls, drop manholes access routes, management of run-off water, risk of landslides, appropriate house positioning and management of sewerage are major aspects to consider while building your house on such a site,” he says.
Nyanzi says the owner should engage the services of qualified people as early as possible. Due to the complexity presented by some sites, it would be good to have the architect with you as you buy such land.
“The most cost effective way of building on a slopping site is by having a split level floor plan. As a matter of principle, all Architects believe in the fact that ‘every site deserves a design and every design deserves a site’; this comes to life especially with hilly sites”, he advises.
Fred Lukoda, a construction engineer says technical people should guide this process very closely. One might want to flatten the site by either cutting or filling. The other option is to design the house to flow with the terrain of the landscape.
Ideas that can make a successful project
Lukoda says some times during the process of construction, soil is removed. In some instances part of a slope on a hill is graded to fit in a building.
There are cases when trenches with channels are dug to drain water away.
Hilly sites will usually provide an opportunity to have a good view around. Work with the architect to exploit any views as much as possible.
How to care for slopping surfaces
According to Nyanzi, channels that have been dug to drain off water can be proving to erosion before grading an area. It is important to look out for things like, the type of soils .
Some soils are loose while others contain ground water. These can make the soil to collapse.
The availability of the materials needed for construction
David Kireli, a civil engineer says the more time the graded slope remains bare, the greater the chances for the soil to be washed away.
The weather condition during the period of construction really matters; it is not advisable to do this during a rainy season.
According to Kireli, for slopping sites, there are various methods used to protect the soil on the slopes. The planting of grass and trees on the sides of the slope help to hold the soil.
This has the effect of creating green vegetation with in a compound. This also helps in the slopping surface taking in same of the water when it rains.
The use of the stones to cover the slanting areas is another alternative.
The stones are constructed on the bare ground of the slopping surfaces.
In other instances, retaining walls constructed out of blocks or bricks are used to keep the soil on one part, with these, special care should be taken as most of the walls are vertical and if not properly designed, they can easily collapse.
Access to services
If the site is slopping, access by service providers might also be difficult. For example running a water pipe uphill for supply might cause low pressure in the taps.
Nyanzi says the architect has to advise the client on what has to be done to keep the pressure good.
For example, in some cases, construction of on-site sewerage can expose the site to possible landslides.