Just like the foundation, the upper slab, which is supported by beams on a storeyed house, is very important in determining the durability of the structure. 

If installed carelessly, it can tear the building apart. 

According to Muhammad Nsereko, an architect with 3M Design and construction, a slab provides the proper support to keep the house strong. 

Hollow slab

In Uganda, there are two forms of slabs mainly used on residential and commercial buildings; solid concrete and hollow (maxi pans) slabs. 

However, Nsereko notes that it is equally paramount to know every bit of both slabs to make the best choice that suits your budget without compromising house strength.

The solid concrete slab

Nsereko explains that a solid slab is purely made of solid concrete and steel bars which is why it is costly. 

Due to its strength, it is commonly used on commercial structures like skyscrapers, arcades and more which hold heavy machinery, vehicles and many people. 

“For safety, it should have a thickness of 0.15metres, 15cm or 250mm and a level of strength of 25,” he says. 

He adds that depending on the functions the structure is to serve, civil engineers usually increase the depth of the concrete to 200cm and above. For example, a structure with parking lots will have a thicker solid slab compared to one with none. 

“The slab once cast is given 28 days to settle and dry, after which, it can serve any purpose it is designed to,” Nsereko elaborates. 

He affirms that apart from supporting any load, a solid slab is a reliable insulator of sound, heat and fire. 

In busy structures, the upper solid slab acts as a strong ceiling for the storey below and also a divider or privacy for the occupants. 

“The construction of a solid slab doesn’t take long, and it can be designed in customizable shapes depending on the client’s taste and nature of the structure,” he asserts.

Pros and cons

According to Nsereko, the strength of a solid slab is unbeatable which is why it should be considered for factories, hospitals, and printing malls like those along Nasser and Nkrumah roads in Kampala.

When it comes to maintenance, concrete is easy to maintain compared to other building materials. 

Nsereko says since homes do not have too much heavy weight, installing a solid slab may be a waste of resources for homeowners. 

Though durable, the solid slab is very expensive to those with limited budgets. You can instead consider cost-effective but equally reliable options like the hollow slab.

Hollow/maxi pan slab

A hollow slab can also be called a voided, hollow core, maxi pan or simply a concrete plank slab. 

The reinforcing system contains a large number of hollow bricks, and steel bars distributed evenly across the entire width with concrete on top. 

Its components include steel bars, maxi pans or hollow bricks at different intervals, timber, BRC or anti-crack to hold the concrete. 

“Steel bars or ribs are laid in between the maxi pans and concrete is cast on top (topping) for extra strength,” Nsereko explains. 

He adds that this kind of slab is also supported by beams and bearing walls that help it to stay stable. It reduces the cost of construction significantly although it can only hold light loads. 

“In Uganda, the standard thickness is 5cm which can increase up to 75cm and more depending on the nature of the structure,” he notes. 

Meanwhile, Nsereko advises that just like solid concrete, a hollow slab should be installed in one go in order to achieve the best results. 

“If you let the bars rust, they will reduce the strength of the concrete. It is safer to gather all materials on time and set the slab at once,” he cautions.