They forgot the most important part about making a structure last 1000 years: it cannot be made of materials that people would conceivably want to repurpose in times of duress or those materials should be in such a form that it is extremely difficult to remove them from the structure. This is how many historical buildings were lost, they were mined for stone to use in other structures. It's also how many modern buildings get ruined by people looking to sell the copper wiring or pipe, and that's in a politically stable era.

A better strategy would be to build the house from massive blocks of the most common stone in the area. The blocks should be large enough that they would require significant effort to move or demolish. I wouldn't recommend using any metal in the structure of the house at all. Even wood could be conceivably stripped in times of need.