Help Please: Retro-fitting an air brick in block chimney

[xeres]

Afternoon all

So, I made a mistake in my first house renovation and in replastering a wall, just blocked up the old louvre air vent. Knocked it through and filled with expanding foam, then plastered over. Now learnt that its actually an air vent to allow flow through the unused chimney and with recent rains, have damp patches come through my walls.

So, can I please implore some advice. I need to retrofit a vent - can I assume this is a relatively simple:
- Drill a hole through the wall, mount a surface louvre to allow air flow?

Any advice or guidance on this would be appreciated. The room is completely decorated (although I do have some left over paint) so wanting to move quickly on this.

With thanks in advance.

 

[Alastairreid]

If the chimney is on an external wall you can put the vent on the outside.

 

[xeres]

Thanks for the reply. Unfortunately that is not going to be possible. Although an external wall, its on the 2nd floor and inaccessible due to the neighbour having a plastic lean to. Only option is to put in place the vent this side.

Thanks

 

[Alastairreid]

If the flue is open at the top try putting a vented cap on it first.

 

[xeres]

Thanks for he advice.

I believe the flue already has a vented cap. It was previously vented at the bottom and I've blocked it up not knowing I shouldn't you see.

I'm Thinking I can just get a big drill bit and put a whole in the wall and surface mount a louvre. Would this be sufficient? This was effectively why was in place before.

Thanks