In 2004 and 2008 a property survey was also carried out, which meant that some respondents received a follow-up visit by a qualified surveyor to undertake a property assessment of their home.
Yn 2004 a 2008 cynhaliwyd arolwg adeiladau hefyd, a oedd yn golygu bod rhai ymatebwyr yn derbyn ymweliad dilynol gan syrfëwr cymwys i ymgymryd ag asesiad o'u hadeilad.