In a roof 1 of a building, a fire-resistant roof construction 3 is present above a fire wall 5. The roof 1 contains insulation layers 1b and 3b on which a roof covering 9 is present. The roof covering 9 is made of flammable material such as bitumen, PVC or EPDM. To make the spread of fire more difficult and to slow down the spread of fire, a fire-resistant layer 11 is present on the roof covering 9 at the location of the entire fire-resistant roof construction 3 and at the location of strips 15 of the roof 1 adjacent to the fire-resistant roof construction 3. This fire-resistant layer 11 consists of panels that are mainly made of magnesium oxide and are attached to the roof covering 9, for example by gluing, sealants or screws.