Gerhard wrote in with the following interesting question about going down, rather than going up, and building a basement
I have a holiday cottage in Stilbaai. I am restricted in the size of the building that I can build. I have started to think about going down and doing a basement. Is it an option in South Africa? Is the square metre cost a lot more for a basement to a ground floor? Can't seem to find any South African info on building basements.
Les, our Architect answered Gerhard as follows:
Building a basement is always going to be more expensive than building on the ground. The items that make it more expensive are the concrete retaining walls that need to be constructed or alternatively, very thick brick walls with reinforced cavities filled with concrete, the waterproofing and also ventilation.
The presence of ground water will need to be checked, particularly during the construction phase as the excavation will have to be kept dry during construction and this may require a pump if it is very wet.
Waterproofing is going to the most important part of the whole project and my advice is to go for the best waterproofing system on offer and employ an engineer to specify what is required.
I would also recommend a concrete additive called Penetron as it will guarantee a waterproof structure.
It is also a thought to have some of the basement as a double volume with the ground floor to allow more natural light into it which is something that your architect could look at for you in the design of the house. The location of your plot could also play a part as soil conditions or the likelihood of rock could make a big difference to excavation costs.
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