6" duct in solid 9" party wall - to remove or not?

Hi all. I'm looking for a bit of advice from the experts round here about the best way to deal with this rather unusual bit of duct running up in our party wall.

When we bought our house it had a redundant old blown air heating system with a boiler in the loft and galvanised steel ducts running to vents all round the house. We've been stripping out the galvanised steel ductwork, most of which is now gone.

The main bit which is now left is this duct shown in the photos. It runs up the party wall all the way from 1 brick below the DPC under the lounge floor, up to just above the ceiling joists in the loft, where it then ran across to a boiler.

It seems a hell of a big bit of ductwork to be running up that wall. The steel itself is about 6" deep, and as best I can tell the wall is solid 9". This house and the one next door used to be owned by relatives - which might help explain any party wall issues there would've been with putting it in there in the first place.

I'm not overly concerned with it from a structural point of view - it seems to have been in there happily for over 40 years. Also, I had a structural engineer come take a look at an unrelated problem with the chimney breasts in the loft. Although the front view of the duct wasn't visible at the time because the plasterboard hadn't come down in the lounge, he saw where the top of the duct emerges up in the loft and didn't seem too concerned about it running down through that wall from a structural perspective.

So I'm wondering what the best thing to do with what's left would be - if not for structural reasons, possibly to help with the sound insulation from next door - it seems like there's not nearly as much wall there as there ought to be.

Not sure what the options might be, but these have crossed my mind:

• Easiest would seem to be to leave it alone, plasterboard back over the top and never think about it again. I'm just thinking that maybe there's something better we should do while we have the chance.
• Take it out and get someone to brick up that section? Is that possible?
• Take it out and fill the void with something else. Maybe even just some sound insulation slabs would be better than nothing?
• Seal the bottom and fill the duct in place with something with enough density to put some mass back into the wall? Concrete maybe?

Having asked around how common blown air heating systems were in residential properties it seems like this might be a little bit on the unusual side, so any advice very much appreciated!

 

Thanks for all the advice guys. Seems pretty unanimous that I should do it properly and rebuild with brick. Suspect I knew that in my heart of hearts, but wanted to check to make sure I'm not making work for myself unnecessarily. At least I have some ammo to justify the time and cost to my wife now

Thanks also for the extra pointers about the general wall condition, damp, etc. Guess I should've put a few more details in the original post but didn't want to make it too long!

Pollowick - the 15mm copper on the right was the gas supply to the boiler for the system, so that'll be coming out with the duct. The cabling is live though, so good advice to take care with that. Hoping to avoid getting fried!

Jitender - you're right, there was originally a chimney breast here, which accounts for the broken header bricks - and I assume also the general poor condition of the wall and unevenness you mention Sospan & Kiab. I've already repointed and re-set the loose bricks where the breasts have come out upstairs, which was in a similar condition. Am planning on doing the same here. 6:1:1 soft:cement:lime sound right for this?

Sospan - yes, definitely problems with damp down there, but I'm hoping now fixed. When we opened up the floor to get at the ductwork we discovered that a load of the plaster and rubble from the chimney removal had been dumped down there (have attached a photo of that mess!). It was filled all the way up to the joists and wicking up moisture to them. That's all been dug out and cleaned now. The ducting was also filling most of the void below the joists, blocking airflow, but it's all come out now. Plus the air bricks have been cleaned up to make sure there's decent flow through them. Hopefully the floor will be a lot happier than before.

Ta for the advice about angle grinding the staples - I'd not thought as far ahead as to the detail of them it out. Might try to see if they'll come out whole easily first, but that sounds like a good call if they won't.

Hoping not to need a lintel down the bottom Jitender. There's a couple of courses of brick left above the slab level, then a gap of one course to where the slate DPC runs, and a bit more space under the duct. Imagine I could build straight back onto what's there, putting in a new DPC after that first brick, then build up on top of that and it'll all get loaded onto the original footing.

Toothing in the new brickwork sounds like it could be pretty hard. Although if it's necessary/better then maybe worthwhile. Any alternatives that might be quicker? The edges will be too rough to use anything like a wall starter, but I was thinking maybe some sort of wall ties epoxy bonded into the brickwork down each side maybe?

 

Ah, cheers Devils advocate. Doing exactly what your name suggests and making it not quite unanimous

Still sounds like removing it and rebuilding would be the best option. Maybe just a bit of debate about the details of how exactly.

 

Yeah, was a bit of a shock to find what was down there when I lifted those boards. I didn't expect it to be nice and clean, but wasn't expecting to be digging out all that junk! Looking much better down there now though. Have just taken these shots of it now. Still seems to be quite damp around the bottom of the sleeper walls, but I'm hoping that's being drawn out of the bricks below the DPC and will dry up given a bit of time.

Good advice about checking the neighbours side Pollowick. Need to remember to do that before I go poking at it. Thankfully we get on well so it shouldn't be a problem and I'll let them know what I'm doing before starting.

No structural work done yet Sospan, but I'm going to replace a few of the joists - there's a few there which have started to rot on the bottom. Luckily it's short ones only spanning the width of the fireplace so hopefully it'll be straightforward. Doesn't look like the stuff was thrown down there to support the joists, laziness seems more likely.

Will probably put some sort of conduit in there for network etc. Reckon you're right KIAB that it'll fit in nicely somewhere behind some studs for plasterboard, rather than channeling up through the brick/block itself.

Bricks are definitely 'sucky' DA I've been using a spray bottle to get them good and wet when I've been pointing and fixing up the walls elsewhere.

Going to be doing the insulation too. Was half considering it before discovering the mess down there. Now I've had to lift the whole floor just to sort it out it's made the decision for me. Also going to be doing IWI on the wall around the bay as all the plaster on that was blown so has had to come down. At the risk of sparking a whole other debate about how to do it...I'm planning to do 75mm celotex between the floor joists held up by some battens, PU foam round the edges to seal. For the wall, parge coat to seal and level it, 50mm celotex onto that, then 25mm battens on the warm side and 25mm celotex fill between them.

I'm hoping that plan sounds sensible as I've done a bunch of reading of insulation posts on here. Not had to post many questions myself as so many of them have already been asked by other people. Have done a hell of a lot of reading of that other stuff though, so thanks to you all for the advice you post on here, it's bloody amazing!

 

Took me a couple of reads to visualise what you mean there Pollowick, but sounds like a good method now I've got my head round it. Ta.

Cheers for all your advice guys. Now just to crack on with getting it done...