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.