You possess a land that is few meters below the adjacent road level. Or you anticipate a situation in future where the road level may be raised and you fear your home will be below the road level. You are considering filling up the land with earth or concrete waste, and build your dream home a little higher than the road level.
Questions that need to be considered
- Is it safe to construct on filled up land?
- What are the measures to be taken to ensure that the house is safe structurally?
- What are the best practices?
What first needs to be understood is that for any structure, there are 3 things to be seriously understood as far as the foundation is concerned -
- The foundation needs to be strong and transfer the load to mother earth. It has to be strong enough to take the loads of the structure above. The capacity of the foundation will be directly proportional to the weight of the structure above. The foundation is designed keeping in mind the condition of the underlying mother earth. In simple terms, if underlying earth is very strong, for instance, if it is rock, then the cost of foundation would be less.
- The foundation needs to be uniform so that differential settlement is avoided. This is the main point because most people make a mistake here. I would not want to go into too much technical details. But what is important to know is that what is required is that suppose the foundation sinks into the ground because of the weight of the structure or because the soil conditions were wrongly assumed, it has to sink uniformly. If it sinks differentially, the structure will have vertical cracks in the walls and horizontal cracks in the floor.
The risks on filled up land
- Consistency of the filled up material is a big concern. What I mean is that when filling up is done, it could be done with various materials. One cannot be sure as to the quality of the material. In my experience, we have had to execute foundation works where the filling up is done with construction waste. The risk is that in such a case, we cannot be certain of avoiding differential settlement.
- Depth of foundation gets that much increased. As I said above, a key parameter of foundation is that the load has to be transferred to the mother earth. Hence, in no case can a building be founded on filled up earth. Technically speaking, it has to be founded on mother earth. Let us suppose the ideal founding depth is 1m below the natural ground level. The house owner decides to fill the earth up by 1m to raise it to road level. In such a case, the ideal founding depth gets increased to 2m. The founding depth never changes, which means that excavation and other construction activities will have to increase that much.