Tanzania is prone to earthquakes and earth tremors. The country has experienced five serious earthquakes since the year 2000. These natural disasters often result in widespread damage and even death. Small buildings and old structures are most at risk when an earthquake strikes, so it is important to improve the resistance of this infrastructure.
Small buildings can be made safer and stronger by taking certain precautions throughout the construction process. The earthquake resistance of buildings has improved dramatically over the past few years. Tanzanian architects and contractors can use some of these tips to make their small buildings more resistant to ground tremors.
Building plans should be symmetrical
Architects need to be aware that symmetrical buildings are more stable and safer during earthquakes than asymmetrical structures. Simple, square or rectangular building plans are more sturdy than ornate designs. Avoid L-shaped and T-shaped houses as these can crack at the corners during an earth tremor. Rectangular buildings should not have a length more than twice the width – this will maximise the earthquake resistance.
Site selection is important
Contractors should avoid building small structures on unstable ground, especially near embankments that are prone to collapse during earthquakes. Sloping or uneven ground should be excavated and graded before any foundations are laid. Similarly, wet soils near river banks and wetlands can also shift and resettle during ground tremors, which could affect the foundations of small structures.
Solid foundations are key
One of the biggest factors affecting earthquake resistance is solid building foundations. The width of a small building’s foundations should be 75cm or more for single-storey houses and 90cm or more for double-storey homes. The depth of the building foundations should be 100cm or more in soft soil and sand, or 50cm in rocky ground. Before the foundations are laid, remove any loose materials from the trenches and compact the ground as much as possible. After the foundations are laid, back-fill them properly and compact once again.
Choose high-quality building materials
The best building materials are high-quality ones that come from reputable companies. LafargeHolcim Tanzania makes a variety of cement products that are strong and durable. Use properly-burnt bricks or well-formed concrete blocks. Brush the top and bottom faces of the bricks and blocks before laying to ensure a clean bond with the cement mortar.
Use river sand for the mortar and concrete as it is the cleanest and best fine aggregate available. Avoid using a coarse aggregate over 30mm in diameter. Aggregates should be well-graded and angular for the best bond with cement. Dry mix the cement and aggregates thoroughly before adding the water. The length of brick walls should not exceed six metres in small homes – use intersecting partition walls to separate long exterior walls for maximum safety during a ground tremor.
Doors and windows can affect stability
Walls with too many doors and window openings are more unstable than solid walls. This means that having too many windows and doors on a wall will make it prone to early collapse during an earthquake. The total width of all the openings should not exceed one-third of the length of the wall. Avoid building doors at the end of a wall – they should be at least 50cm away from the edge of a wall.
Building a solid roof is important
In structures with a roof span of over six metres, use proper wooden trusses instead of rafters. These are far stronger and more durable than simple rafters. Small buildings with four-sided sloping roofs are stronger than two-sided sloping roofs. This is because the gable walls are prone to cracking and collapsing during an earthquake.
Retrofitting ensures stability in small buildings
Retrofitting is the process of building a structure such that all elements act as integral units of stability. It is the best way to achieve the maximum safety of a building. Examples include:
- Anchor roof trusses to the walls with metal brackets.
- Strengthen gable walls by inserting a sloping belt.
- Strengthen corners of the building with seismic belts.
- Anchor floor joists to the walls with brackets.
- Provide vertical reinforcement between different floors of a building.
- Encase wall openings with reinforcements.
These tips will help architects and contractors to make their buildings more resistant to seismic activity. Earthquakes and ground tremors often result in building damage or total collapse – neither of which are desirable for the safety of the people living inside the structures.
LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges.
LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.
At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.