Sealing/insulating stud wall for smell insulation

[GT3000]

Hey all! I've done a search, but struggling to find a previous post on something similar.

I have an issue in our home, where by our neighbours are extreme chain smokers of cigarettes, and their son a chain smoker of weed, so we have an issue of nasty smells infiltrating our house! And with 2 children under the age of 3, it's not a nice issue. We've spoken to the neighbours, who frankly couldn't give a s#!t. We live in a standard 1930s 3 bed semi. Our house was extended by previous owner. We have a front sitting room, and then a kitchen/diner in the rear extension.

I've narrowed down the smell coming from behind the party wall where the kitchen (highlighted in the image). It seems as though when the previous owners did the extension / new kitchen, they built a stud wall where highlighted (it's hollow when tapped). There is an open area of the wall under the kitchen units which WREAKS of smoke.

Ideally, I do not want to have to rip out the kitchen (there are units on the wall, as well as the floor), and then pull down the wall to seal the gap. I was thinking to have the wall filled with some sort of foam / insulation, which should then seal any holes (the area in blue is where a chimney used to be). What would you good folk suggest? Drilling a few holes in the wall and filling with expanding foam? Getting someone in to fill it properly (who would I search for?).

Would appreciate any help/advice, as it is driving me (and especially my wife) insane.

 

[Deluks]

Your solution sounds a bit hit and miss, maybe worth a go, but if you have any pipes or cables running through that area, you don't want to go smothering them in expanding foam.

Underneath floors is another weak spot, there could be gaps around floor/ceiling joists that are allowing air movement between the properties.

Sounds like a job for an inspection camera.

 

[GT3000]

So I've checked the joists on the first floor, and totally sealed those off with foam (not that there were gaps to begin with anyway). And the smell is def not coming from the ground floor joists, as there is no smell under the floor, just the wall.

I like the idea of using an inspection camera!

 

[^woody^]

You will not make your house airtight.

The answer may well lie in installing a Positive Pressure Fan.