Blocking a utility duct

Our block of flats has been designed with an internal utility duct in the kitchen which carries water to and from the flats. The problem with this is that there is pipe running between the three flats, and therefore, because it has been poorly sealed in building, air can freely flow up from the ground floor flat (we are in the middle flat). Downstairs are heavy smokers and, guess what, our flat reeks of smoke. It took us several months to work out where it was coming from!

As we are not smokers, we think this is really disgusting! Why we should have to suffer with someone else's smoke in our own home - but anyway don't get me started...

The DIY aspect of this question is what people's recommendations are for providing a semi-permanent seal.

Considerations:
- It's not a straight hole down all the way (as far as I can tell) - ie if I dropped something non-liquid down the hole it wouldn't drop into the flat below, but it might go a fair way down. It's rubbly stuff maybe six inches down.
- The duct would need to be sealed as well as possible at floor level as the stopcock is located higher up
- It's awkward to get to - there are worktops/cupboards built in front of it. I tried cutting cardboard to size with holes left for pipes, which would work if I could get the cardboard in there in the first place.
- obviously whatever is used needs to be fairly flexible but also provide a good seal (even if it needs to be replaced periodically)

My wife went to B&Q and had a variety of suggestions including
* papier-mache (I think this would make the kitchen damp?)
* wood or cardboard template to cover the hole (access problems, see above)

I had ideas like bubble wrap or loft insulation that can be moulded around the pipes and stuffed in the hole. If it's porous then the smoke may eventually penetrate the material and this would need to be replaced - this is OK so long as it's not every week! I have some sealant which can be used safely around pipes, but obviously this only works on small gaps so could be used in conjunction with other material.

Any ideas would be greatly appreciated – it’s really irritating me now!

I quite agree about other people's smoke - filthy habit. It doesn't sound like that building complies with fire regs regarding appropriate fire-stop.
What I would use would be a can of expanding foam, as long as there are no electric cables though. Wickes, Screwfix, Machine-Mart etc.

This was our first idea - it never came up as a suggestion in B&Q. We thought about probably having to apply several layers, starting from the edges otherwise we'd waste a lot squirting down the hole!

I should've given dimensions - the casing for the duct is about 30x18cm but the hole is smaller though. There is one water downpipe of approx 14 inches circumference, and another smaller pipe probably only 2-3 inches diameter. No electricity comes in that way.

Given your comment about the fire regulations, might some fire-retardent material be advisable? This would help on two levels (mind you, if a fire broke out downstairs I think the duct would be the least of our worries)

Have you ever used expanding foam though? There really is a big volume from one can and it sticks ok. It's very easy to use too much when filling round window frames. You say there is rubble about 6" down so if you can get the tube from the nozzle down there I don't see why it wouldn't work. I don't know about fire retardant materials but if it doesn't comply now then you have improved things by stopping smoke passage which is the real problem in a fire.

I've not used expanding foam before – I haven’t even seen it. I’ve only seen the sealants which don’t work on larger areas. How does the foam set (based on the ones you were recommending)? I presume it won’t cause any damage to the pipes etc.?

I’ll take a look and see what’s available. A “squirty” solution to this problem would seem best, given that I have to crawl into a cupboard to get to the hole!

It's ok to seal around pipes but I don't know the chemistry how it sets. Do a google search on it.
I think there is a question mark about contact with electrical cables and that may be why cables aren't allowed in the cavity anymore, as foam was often used to insulate the cavity. It's more blown fibre these days.

An expanding sealant would probably be the most suitable fix.

There are three main variants of expanding sealant: polyurethane-based, polyisocyanurate-based and latex-based. The first two expand by up to 40 times the volume so will tend to displace anything loose and can sometimes distort framework etc. Latex expands by a much lesser amount and is a bit easier to control.

Polyurethane and polyisocyanurate-based foams are the most commonly available but very messy to use and you need to take precautions when using them as they are a real bugger to clean off hands, clothes and furnishings. Wetting the area to be filled with water will help adhesion and curing. All are sold in aerosol cans and can be found in DIY stores and builders merchants. Read the instructions first!

If you've got any left over, you could always stick some foam in your nicotine-dependent neighbour's front door lock for a laugh. Or if they really get up your nose, their boiler flue. Have fun.

Good luck with this one, I have the same problem (I am a semi-militant non-smoker, my downstairs neighbour smokes so much his face is the colour of nicotine).

I would be interested to hear the outcome of this one.

At least try something easily removeable before using expanding foam, you could be replacing one problem with another !!

Some experimentation required ref filling material, before trying the irreversable .... IMHO.

P

pipme said:

At least try something easily removeable before using expanding foam

Click to expand...

Such as?

londonbluefish ruminated :-

... I had ideas like bubble wrap or loft insulation that can be moulded around the pipes and stuffed in the hole. If it's porous then the smoke may eventually penetrate the material and this would need to be replaced - this is OK so long as it's not every week! I have some sealant which can be used safely around pipes, but obviously this only works on small gaps so could be used in conjunction with other material...
Well worth a try, 'suck it and see' sounds easily reversable if inadequate !!

Can you not cut the cardboard templates into smaller sections and and use sealant to bond together in situ ?

Is it too dificult to seal duct space with respect to the room ?

Failing all else a proper cut and shut job will require some kitchen dismantling .. not a pleasant prospect, but not impossible.
Of course we cannot 'see' the problem ... makes a lot of difference.

P

Would bags of dry sand(freezer bags) rammed round the pipes and the hole do the trick?

Would bags of dry sand(freezer bags for example)) rammed round the pipes and the hole do the trick?

Sorry must of pressed twice!