6 letters covered with mould or containing it.

m...

in bad condition due to use. Synonym of scruffy

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

 very dirty and unpleasant synonym of sordid

5 letters having a lot of dust

d...

not bright

does not have enough space for people to be in it

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

unpleasant and or poor quality