What you should consider before expanding your house to meet your needs

In general, there are three kinds of changes you are likely to make. The first is a modification to the exterior such as a parking area or a roof extension in the front or back of the house. Second, you may increase the functional space inside the house, such as a kitchen or a living room. Third, you may add rooms for newlywed sons or daughters or for elderly people.

But before expanding a house, there are a few things to consider.

1. Consult engineers first

Engineers must be brought in to check whether the existing structure can support the planned expansion and for safety reasons. Choosing light materials for the expansion is recommended.

Believing that an existing structure can support a small expansion could have disastrous consequences because the original design was calculated to rely on a certain number of foundation piles and other supportive structures, based on a certain number of habitants, furniture and other equipment. In general, buildings in Bangkok use I-shaped foundation piles varying in length from 12, 14, 16, and 18 to 21 metres depending on the condition of the soil in different areas. This calculation normally excludes expansion phases, and this can render problems such as cracks, sinking and leaking when the expansion takes place without consultation with engineers. Sometimes these are so severe that the whole house has to be demolished and rebuilt.

Therefore, the ideal expansion should be separated from the original structure’s foundation piles, beams and roof structure.

2. Architectural design 

Expanded space should correspond to the existing house design both in materials and appearance. Architects can offer three-dimensional models to show homeowners the difference before and after expansion. Without seeing the distinction beforehand, some owners would have to live with an undesirable expansion forever.

Ventilation must be a consideration for the expanded house. Many expansions prevent air from flowing from the front through to the rear of the house. When this happens, heat can accumulate inside the house so that air-conditioning is essential. Therefore, the expansion must be designed to ease the airflow.

Expanded space must take into account the need to maintain natural light. Expansions often block natural light from the house, sometimes making the hallways and stairwells gloomy and causing them to depend on electric light all day. 

3. Legal issues and impact on the neighbours

Most expansions are illegal because laws regulate the space required for each type of building, and most buildings take up the full space. Housing authorities will take steps if someone files a complaint. Therefore, before undertaking an expansion, you should inform the neighbours what it will look like so that it does not affect them negatively. 

Try to avoid building expansions close to a neighbour’s house. For example, do not install ventilation panels close to an adjacent home so that noise, light or smells disturb the neighbour. The expanded area must have rainspouts installed so drained water does not spill into the neighbour’s area.

4. Acquiring subcontractors

When selecting subcontractors, price is not the only consideration because in many instances, they will bid low just to get the job, which may later compromise the quality of their work and add to the cost. At worst, they could leave the job before completing it. Therefore, you must look for subcontractors based on their previous work records or ask for recommendations from your acquaintances. However, to avoid being cheated, the owner needs an engineer to oversee the bargaining and to organise the work phases.

All of the above may sound complicated. But ending up with an expanded house that you cannot live in and that needs to be demolished or faces complaints from your neighbours is not worth the cost, time and stress. Hence before expanding your house, consult experts and consider all factors carefully so as not to be disappointed later.