At common law you have a right of action against a builder for structural defects within 6 years of the contract to build. However, what happens if your builder is a company which goes into liquidation, or your builder has no assets in his name when you seek to recover damages against him, or if he dies? That is where Homebond steps in. It is a kind of insurance against those situations ( among others). If you don't have this homebond protection you leave yourself open to future problems. However if you have a proper professional engineer with professional indemnity insurance and he signs off on each stage ( he is employed to supervise the build by you) then you have the protection of his insurance too as well as the fact that it will obviously be less likely that there will be a problem because of his supervision. There are other kinds of insurance besides Homebond too. If your builder is good, and your engineer is good, you may decide to do without the added Homebond protection.