I have just been directed to this site via google and have a similar problem. Did you resolve this and if so how?

I really feel for you, cannabis is illegal and I hope it stays that way.

It is antisocial, smelly and very unhealthy. You don't have to put up with this situation  - I suggest that you call 101 and make your concerns and complaints known to them. 

It might be worth checking the seal on your son's bedroom window and seeing if there's anything you can do to prevent/reduce the smoke getting in. cant think of what else to say really.

Do contact your safer neighbourhood police team & the housing officer, it's not only illegal but also highly anti social. You shouldn't & don't have to put up with it.

Good luck

OK - just had a word with the mom next door who was very nice about it and said "she will take a look"..... let's see! I didn't specify "cannabis" but I did say a smell - I think its smoke via chimney stack and floor boards... Was really nice that she was not being defensive at all... Fingers crossed!

And I have the contact details now for the Housing estate guy if need be! Thank you all SO SO much for all the advice and kind words of support!

OH I feel for you so much. I had this problem in June. I have had the smell of it waft into my house or worse, on my clean washing outside a few times (we part own part rent through family mosaics) and the first time it really bothered me I just knocked on the door and said 'I'm really sorry but your cannabis smell is coming into my living room and I have a baby' and he seemed really mortified and it stopped for ages. Then in June I think they began to do it more and more and also another neighbour above started too! My elderly grandmother was here from Scotland and I was 6 weeks pregnant with Hyperemesis which the cannabis smell coupled with the intense heat of london this summer, made it a million times worse. I first went to knock on their door, but had to call the buzzer and I admit I flipped out and said if they didnt stop it I would call the police. It didn't stop, so I called the police. I had to badger 101 a lot. Cannabis posession is Illegal, it's Illegal to smoke, it's a class B drug I think. It was made class C and now it's back to B i THINK but I may be wrong. I had to give them a hard time, also my housing association and what worked for me was sending a tweet to the housing association, my local MP (I was sooooo sick and desperate and like you, the majority of the smoke was coming right into my now toddlers bedroom window!!!) Also, I tweeted Family Mosiaic and I complained and complained and it has stopped. They denied it was them but funnily enough since the Housing officer went over to speak to them, I haven't smelled it since....it was them! I even told one of them off for it when he was lighting up on the adjacent balcony! Anyway I also told them I was having midwifes making home visits as I was planning a homebirth and I really laid it on thick about how much it was affecting my health.

You DON'T have to put up with it. It IS illegal. Good luck .x

Aw thank you all so very much! I will go speak with then this afternoon - hopefully the mom at least will be really helpful. If that doesn't work then I will ask the council what to do. At least that way I would feel I have been fair!

Will keep you all posted

I have had a similar problem in the past with neighbours but on both occasions the issue was amicably resolved. In a nutshell I sought advice from my brother-in-law who rather conveniently was a senior detecive at Scotland Yard. After leaving a few notes in our communal hallway (we have an apartment in a large house) my inclination was to phone the police - he advised against this and suggested that rather than using the 'hammer to a nut' approach that I leave a polite letter in the communal area highlighting something along the lines of (a) the problem - smoke permeating into our home (B) why is was causing problems - smell / potential affect to health etc (c) suggest a solution (i.e. if they wish to smokem - go outside away from the property (d) next steps if the problem continues (ie will call the police). In our case it worked - I came home the same night and basically every property owner in the house had signed the letter (it turned into a mini petition!) and the person involved - whose new partner was the smoker - took heed. I understand that your situation is slightly different but it may be worth consiudering writing a letter (take a copy of it) in the first instance to make them aware of the problem it is causing you etc. If that fails phoning up the antisocial unit (may have the name wrong!) sounds like a great idea!

I really feel for you. Not only does smoke smell awful, it's a health worry. We had some downstairs neighbours who moved in and started smoking heavily and it came up through the floorboards in to our flat, it stank and really stressed me out. I went down there and asked nicely if they could stop. I told them that I was asthmatic and pregnant (one was true) and it was really causing me problems. They just about stopped/smoked outside which was a relief. We also put some carpet/rugs down in the rooms with floorboard which helped.

Good luck. Neighbours can be a really difficult.

I really feel for you. We went through exactly the same thing a few years ago and it made our lives a nightmare. Our little girl was a toddler at the time, and the woman who lived downstairs at the time was a heavy smoker, and although it started off as just "normal" smoke (which sometimes caused a haze in our living room and kitchen), we started getting an increasingly strong cannabis smell coming through. We started off by just mentioning to her that we had a problem with smoke coming through, in the hope that she would realise that we had noticed the smell, but it made no difference. As far as she was concerned, she owned her house and could do what she liked in it. Which is fair enough, except that what she was doing didn't stay in her house! The constant smell of it made me feel sick, and on one memorable occasion, my daughter was running around the house, arms waving, acting as though she was high. That was the last straw. I called in Environmental Health at Wandsworth council and the local police, who were both very helpful. They took the complaint seriously, especially because a child's health was involved. For us, unfortunately, the problem was never fully resolved, and, as we were renting, we just moved out. However, if we had stayed and continued fighting it, I don't doubt that between Environmental Health and the police, they would have got it sorted out. If she had been Housing Association, it would have been dealt with even quicker, because we could have complained to them, too.
Don't feel guilty about kicking up a stink. It's your child's health at stake, and the nasty, second hand chemicals do have an effect! Good luck x

Oh! Had no idea we can call police/anti social behaviour for this kind of thing.... Will try the latter at least and see what they say. Thanks!!

Please, call the police on number 101 and the anti-social behaviour team. The latter will need to come to your house and see of you can really smell in your kids bedroom. If they agree, they will send them letters and they can be evicted. It does work.

Do not put up with this. Cannabis has a strong smell and is illegal. He has to smoke somewhere else.

Sounds like you've thought of everything I would have done. Insulation under the floor boards or a very good underlay under your carpet and carpet over the old hearth right up to the back of the fireplace might help.
Best of luck. What a horrid thing to be having to deal with.

Thanks for the advise! The chimney is already blocked off but since its not "sealed" along the brick maybe thats how its seeping through especially where the floor boards are "incomplete". My builder thinks I should report to the council as its illegal to consume cannabis (I thought it was just dealing that was illegal but what do I know!)...but not sure if that will help. Maybe I should just man up and just walk over and ask them nicely if they can smoke elsewhere...and just say "smell of smoke" in general....?

In terms of smell travelling, is it possible that your fireplace and the fireplace in the adjacent property share a common chimney stack. This is not uncommon in Victorian terraced properties. The smoke is going up the chimney on the neighbour's side, going across and coming back down the chimney on your side. If your fireplace is open and you do not use it, it may be worth putting an inflatable balloon up the chimney to block it off. These are easy to put on/off and only cost about £20. If you PM me I can give you details of where we got ours from (online).

I have a lot of sympathy for you.