How to create airtightness at first floor to exterior wall junction

Blisterman

Looking at beefing up the insulation and airtightness to an old Victorian terraced house by internally dry lining.

There are at first floor level, floor joists fixed directly into the front brick wall with floorboards laid on top as the floor finish.

It's easy enough to form a relatively airtight junction in the ceiling below.
However, I don't think It'd be possible to make the floorboards airtight,and it'd currently just cause a direct route for air inside the house to bypass the drylining from underneath.

There's no easy way to lap a vapour barrier around the joists because they're fixed into the wall.

Would I be best off just spraying a load of expanding foam into the area where the joists meet the wall? Or does anyone have a detail of how this can be solved?

I'm sure it's an extremely common scenario, but I'm struggling to find a solution online.

Calahonda52

The foam is the wrong answer for two reason
1: it is not a/t
2: it will retain moisture at this crucial junction and over time rot the joists.
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Are joists visible for above or below?

Blisterman

They are accessible from above, though I'll probably end up re-plastering the ceiling completely.

Calahonda52

Blisterman wrote: »

They are accessible from above, though I'll probably end up re-plastering the ceiling completely.

Any pictures?
It is possible to make it substantially airtight but it is time consuming.
The different ideas are a fn of the substrate between the joists

Lumen

"Victorian brick" seems significant. Driving rain on that wall?