John Kelly wrote:
My extension was built and I'm about to start laying topsoil and grass
and generally finishing off. I'm a little unsure of how high I can go
with the topsoil. Obviously I can't go above the damp proof course and
that's too high up anyway but I'd like to go about 2 bricks below it
as that's what it is around the rest of the house. However there are
gaps between some of the bricks that low down - it's about 5 bricks
between gaps. Can I go up past this level or are the gaps there to
let air in?

150mm down from DPC is the maximum you can go to with your soil/turf (or
about 2 bricks with joints)
The holes are weep holes and are there to allow moisture to drain out of the
cavity....you can go up to the weep holes but I wouldn't cover them if I
were you - the amount of moisture they will deal with in a year would
probably not even fill a bucket, but if left standing in the base of the
cavity, it will cause lots of other problems, especially when it freezes.