Govt bans steel-timber house building method

Government has banned the use of steel-timber concrete composite building method in Uganda, citing structural safety risks.

In multiple interviews, engineers welcomed the decision, which they said many developers prefer because it is relatively cheaper compared, for instance, to the steel-concrete composite technique.

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Works Minister Katumba Wamala in a statutory instrument issued on September 19 but gazetted on September 23, noted that:

“In exercise of the powers conferred upon the minister responsible for building operations by Section 42 of the Building Control Act, 2013, and after consultations with the National Building Review Board (NBRB) … the use of steel-timber concrete composite building method is not safe and is prohibited in any building operation.”

The Section provides that the minister may, after consultation with the Board, and “upon being satisfied that any method or material used in a building operation is not safe, by notice published in the Gazette, prohibit the use of that method or material in the building operation”.

The law provides that such a decision can only be challenged at the High Court and a person “who uses a prohibited method or material contrary to a notice issued under subsection (1), commits an offence and is liable, on conviction, to a fine of not exceeding forty eight currency points (Shs960,000) or imprisonment not exceeding two years, or both”.

Works ministry Permanent Secretary Bageya Waiswa told this newspaper that the ban had been precipitated by findings in a report of an evaluation carried out by the National Building Review Board (NBRB).
“They (NBRB) did a technical assessment and came to the conclusion that the method is dangerous. They filed a report that detailed the dangers. It is on that basis that the minister issued the statutory instrument,” he noted.

The PS, however, declined further comment, referring out inquiries to NBRB.

The Board Spokesman, Mr Herbert Zziwa, confirmed the findings, but similarly declined discussion on details of the report. 

NBRB 2021 study
However, other sources at NBRB said a June/July 2021 report showed 80.5 percent of the buildings under construction in Uganda’s capital, Kampala, and new cities did not comply with provisions of the Building Control Act, presenting a risk to occupants.

The study, among others, focused on whether engineers and contractors were following approved building plans and terms for issuing occupation permits, nature of professional engagements and drainage systems provisioning.

The researchers examined 5,939 structures, which included 2,606 completed buildings and 3,333 sites under construction.

“The overall compliance level of the active construction sites was  at 19.5 percent, acquisition of building permit at 6 percent, supervision of the building by professionals 6 percent,” the study read in parts.

It is not clear whether that report which was issued in Kampala in October last year constitutes what informed NBRB Board’s recommendation to slap a ban on the use of the steel-timber concrete composite building method. 

Mr Zziwa said NBRB has a detailed technical report which it needs to first break down before issuing a public statement on the matter. The statement, Mr Zziwa said, is to be issued at a press conference today.
“… We are going to … give details and explain the study, recommendations and steps that can be taken for the existing buildings that were constructed using that method, what will be done to those buildings, and also going forward what should be done,” he said.

Engineers’ take
Mr Andrew Muhwezi, the president of Uganda Institute of Professional Engineers (UIPE), said he understood Gen Katumba’s actions as intended to avert a “catastrophe” because “the strength of the structures (built using the said method) have been found wanting”.

“… many of them (buildings) have been collapsing. I think the minister’s legal notice is supposed to be like a mitigating measure to say, ‘please, let’s hold on and we first provide national guidance in this design arrangement and also train the different players so that we do not have continuous catastrophes,” Mr Muhwezi said.

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The steel-timber concrete composite building method is a hybrid that has assumed increasing prominence in much of the western world in recent times, but Mr Muhwezi said the method was being implemented without it being subject to local tests and standards.

“Somebody went and benchmarked this kind of hybrid arrangement from somewhere and came and started piloting it on one site, then others picked the idea and replicated it across without local guidelines, without local standards or adaptation to international standards. What has been happening is, of course, catastrophe,” he said.

Alternative fact
Research carried out by the University of South West Sydney in Australia concluded that timber as a lightweight and sustainable construction material can be sufficiently used in conjunction with steel and concrete to develop robust and environmentally-friendly structures.

Associate Professor Hamid Valipour, who carried research on innovative hybrid/composite timber-concrete and steel-timber connections and structural systems, argues that the method is much faster than use of the steel concrete composite methods.

“Currently, buildings consist of reinforced concrete or steel-concrete composites, cast in situ. Concrete is poured into formwork and propping is then required for at least a week. This is a wait of at least 10 days between storeys. Building with steel-timber composites means there is no waiting and upward construction can be seamlessly ongoing,” he wrote.

However, Mr Moses Tiberwonda, an engineer who speaks for the Uganda National Association of Building and Civil Engineering Contractors (UNABCEC), said it is not the only method that guarantees swift construction.

“There are some other methods which are faster, but have not been used. Spear House [in Kampala, for instance] was constructed of steel. It is also faster and I don’t think it is as risky as this method. We should not start killing people because it is a faster method,” he argued.

In his research, Prof Valipour argues that besides being much lighter, the steel-concrete composite method reduces the risk of injuries, increases efficiency of movement, lifting and placement of panels, reduces noise and pollution associated with construction activities and the composites are easy to dismantle and facilitate recycling or reuse.

Right versus wrong 
Eng Tiberwondwa counter-argued that whereas the method has been internationally acclaimed, the steel-timber concrete composite is being applied wrongly in Uganda.

“We are talking about a situation whereby someone is using small universal beams and he is combining it with timber and concrete. When you look at the kind of construction it is like he is doing a ceiling, but he continues to the next floor,” Mr Tiberondwa said.

He added: “The way they join the horizontal members and the vertical members, that joint is very weak. When you are joining a vertical member and a horizontal member, industrial welding is one of the methods. The other one is using bolts. And in these buildings I have seen, bolts are not being used, the welding that we are seeing is very weak. It is not industrial welding. It does not pass the test.” 

Structure built using steel-timber concrete composite are designed to last for 20-30 years, but the buildings are weak. “If you get a tremor of any magnitude,” he said, “[the] buildings will not stand. You are putting the lives of people at stake.”

Earlier, UIPE President Muhwezi said the “combination of pillars is not a conventional structure”, adding that standards have to be set in place to ensure that both the designers and contractors design and develop structures that are strong and robust, which has not been the case with structures constructed using the banned method.

Eng Muhwezi said whereas the method has been tested elsewhere, there is need for national guidance and training of different actors in the construction industry on the design arrangement.

Salvageable?
It was not possible to establish the exact number of buildings that were constructed using steel-timber composite method, Tiberondwa said such buildings could still be modified to make them safe.

“The developed countries use that method because they have addressed the weakness in the method. Similarly, if we find a building and get people to understand the structural weaknesses, we can modify the areas where there are weaknesses,” he added.

The method
A composite material is made by combining two or more materials – often those with very different properties for purposes of construction. The two materials work together to give the composite unique properties.

Steel Concrete Vs Steel-timber concrete composite.
Steel-concrete composite uses concrete’s compressive strength alongside steel’s resistance to tension, and when tied together this results in a highly efficient and lightweight unit that is commonly used for structures such as multi-storey buildings and bridges, according to Eng Moses Tiberwondwa.

Steel-timber concrete structures on the other hand use, he said, the strength and stiffness of the concrete; the tensile strength of the steel; lightweight, energy andappearance of timber in similar structures. The concrete slabs protect the beams of timber from direct contact with water. That is vital for ensuring durability.

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According to Eng Tiberwondwa, the incentive to employ the banned method has been the relatively cheap cost of construction.

“It is generally cheaper because contractors move away from the use of huge volumes of steel required in the making of reinforced concrete and steel structures that are necessary when you are using the steel-concrete composite method.