6 letters covered with mould or containing it.

m...

5 letters having a lot of dust

d...

does not have enough space for people to be in it

 very dirty and unpleasant synonym of sordid

unpleasant and or poor quality

not bright

in bad condition due to use. Synonym of scruffy

of furniture or parts of buildings weak, old and likely to break

in very bad condition and in need of repair

unpleasant because there is a lot of air coming in

 in bad condition and not cared for

having far too many things in an untidy way