The snagging survey is designed to check for defects with a new-build home. It is a list of all the problems found during the inspection which the developer must fix quickly. Ideally a snagging survey should be done before moving into the new property. Some developers may have a policy of not allowing a snagging inspection prior to legal completion - in such a case a snagging inspection should be conducted immediately after legal completion. Technically you can have a snagging survey done at any time during the first two years of occupation.
The snagging survey is a thorough non-intrusive visual inspection of the property, looking to pick up everything from minor issues, like doors not closing properly, poor finishes, poor workmanship, to more serious problems like possible structural issues.
New-build homes will come with a 10 year NHBC/Premier/LABC warranty to protect the purchaser against any latent defects. The developer/builder is only responsible for the first 2 years and provides cover for every defect of the property, and there is no limit on the number of snag lists that can be submitted in that 2 year period. In years 3 - 10 the warranty provider only covers structural defects.