Air Bricks... how many and where to put them?

A question about : Air Bricks... how many and where to put them?

As part of the next stage in our refurb of a 2-bed victorian terrace (circa 1880) we'd like to tackle sub floor ventilation and damp proofing in the front bay area of our house.

Our structural survey highlighted 'inadequate sub floor ventilation' and ground floor damp in the front bay area caused by the lower bay having been rendered poorly and a raised external concrete hard-standing blocking the sub vent and bridging the DPC. Here's a photo of our current bay area:

https://bpkersey.com/images/front-bay-1.jpg
https://bpkersey.com/images/front-bay-2.jpg

Our builders plan is to completely gut the concrete hardstanding and replace it with a new level hard-standing lowering it to the required depth to stop it bridging the DPC. Is this the right course of action?

Our survey also recommended installing more air bricks (even one under the front door sill). Neighbouring houses all seem to have 2 or 3 in that front bay area as seen here:

https://bpkersey.com/images/neighbouring-front-bay-1.jpg
https://bpkersey.com/images/neighbouring-front-bay-2.jpg

... but our builder says that isn't necessary and we only need the one?!

Any thoughts on this, should we get more air bricks installed as per the survey or listen to our builder?
And should these bricks enter and ventilate beneath the internal floorboards, or should the vents be above floor level with a visible internal grill on the wall below the bay window? I presume below floorboards to ventilate the timbers but our builder mentioned above floorboards!

Again... confused about air bricks and where they should go?!

Best answers:

• We have a victorian terrace and as far as i'm concerned, the more the better.
  The problem area in our house is the front hall - getting a builder to install an airbrick under the doorstep has made a massive difference. It's only been there since Oct (ie. autumn, winter) and the damp smell has completely gone and the underfloor has improved massively.
  THe important thing in a terrace is to think about cross flow of air. IS there sufficient air bricks across the back as well? We have a massive conservatory which the installers neglected to include airbricks (therefore blocking 2 of the 3 existing air bricks).
  ANother thing is to look under the floor - which way do the underfloor pier walls lie? are they honeycombed for air flow? do the internal walls have vents front to back under the floor? Is the under floor space full of carp (ours was rubble and mud up to the joists!)
• I'm not sure where that external air brick in my 1st picture leads to although it's position on the outer wall is higher than the internal floor level ... but there's definitely no sign of it exiting on the interior wall above floor level.
  Is it possible that this air brick is above ground on the outside and below floorboard level on the inside, using some sort of periscopic channel??
  I'm at the house this afternoon and will check if i can visibly see where that brick exits (the electricians are in and some of the floorboards are up).
  We have solid walls, not cavity.
  Air bricks at the back of the property have been blocked by a kitchen extension built around 15-20years ago. We are having a new kitchen extension built in May and will have the rear property ventilation issues solved then to achieve air flow right through the house.
  The builders are working on the front exterior (brickwork and hard-standing repairs) next week so we'd like to tackle the front air bricks now.
  So... do you think 2 x new air bricks in the bay (LHS + RHS when looking at house), the current air brick in the middle of bay and one more under the front door sill would be the right thing to ask for? As in this:
  https://bpkersey.com/images/neighbouring-front-bay-1.jpg
  Or is it too many / too little?
• If you want to ventilate the sub floor void then the air bricks need to be below floor level. If you want to ventilate the room then above the floor level.
  This is something on the TODO list for our new house as it also has high ground levels and only one air brick with others having been covered by extensions. It seems like an easy enough DIY job.