Another critical issue is that the engineer or architect who under the DB&P Act has overall responsibility for the project has to guarantee the outcome for 10 years. If a large strata building gets its windows replaced (say) and the DB&P law applies, the window company only guarantees the outcome for 6 years. Therefore the engineer or architect has to carry the risk that the new windows will have problems for the final 4 years. So they over-engineer the project – to minimise the risk that they will liable to repairing the failed water-proofing (say) 8 years after the project is completed. The resulting new windows will be very high quality, but will obviously cost a high amount to achieve this outcome, or more than may be needed and sensible!