An NHBC guarantee is a structural defects guarantee valid for a period of ten years from the date it is issued.  This warrants that the property was built according to minimum building and design requirements for construction and finish, including statutory Building Regulations.
The Scheme is split into two periods.  The first is for damage or defects to the property which occur during the first two years from the date of legal completion, the second is for damage to specified parts of your home (essentially the structural elements) in years 3 to 10.
On the sale of the property within the 10 year period, the balance of the cover can be transferred to the new owner.
In essence the warranty protects you against the cost of having to rectify inherent structural defects discovered within 10 years of the property’s construction.  Should you discover any such problems in the first two year period your first step should be to contact the original builder/vendor and ask them to rectify the situation.  If they fail to do so or you are within the second phase of cover, NHBC will step in to mediate on your behalf in the first instance, and cover the cost of remedial work.