Disappointed with both FNB and Outsurance

In 2017 just started my career I.was so happy I bought a house via agent which by the way helped me app**** for housebond FNB approved.20 year contract they even suggested I get home insurance with Outsurance both of their assessors approved the house..deductions started no complaints..Now 2019'January the roof of the garage collapsed actually potion of it..I was also.not worried called my insurance outsurance and they send their assessors after that claim rejected they said because it workmanship..hence the house is as we bought it, no alteration meaning was never in a good condition..my question how did FNB and OUTSURANCE approved bond and insurance and send assessors and approved but now when it time to.claim it workmanship??????