Building new homes can be a time consuming, expensive process. In Africa, communities are going back to an ancient technique to build sustainable homes that don't break the bank.
Since the year 2000, the Nubian Vault Association has been using masons with knowledge of the Nubian Vault technique to build roofs out of mud bricks as well as training up the next generation.
This is helping to reduce communities' reliance on materials such as costly corrugated iron and sawn timber beams.
The bricks used by the association and its builders are made from local earth and water and then dried in the sun.
Houses with this style of roof are said to be cheap to make, retain heat during the night and remain cool when the weather is hot.
"In ordinary houses cement and raw materials are very expensive and have to be brought in, they are not found in my village," said Bassirou Coulibaly, a Nubian Vault Mason from Niéna, a rural community in the south of Mali.
Alex Dembele is national co-ordinator for the Nubian Vault Association.
"The advantages of working with (the) NVA are not only a reduction in construction costs," he said. "The houses have a very stable climate all year round… (and) it also provides employment for the community," he added.
According to the association, as of September 2015 380 Nubian Vault masons – in Burkina Faso, Mali, Senegal, Benin, Ghana and Mauritania – had been trained, with more than 1,800 Nubian Vault buildings finished in 700 locations.
"Our slogan is: Roof, job, market place," Dembele said. "The technology is in place to be able to pass these skills onto a great number of people," he added.
The association says that 20,000 people have benefited from their buildings, with around 55,000 tons of CO2 equivalent potentially saved when compared to other techniques.
The association also states that its economic impact on "local economies" is more than €2 million ($2.27 million).
For Coulibaly, there have been economic as well as housing benefits. "Once I've finished building my house, I have other clients waiting," he said.