Green Building Forum - Joists around chimney Tue, 19 Dec 2023 04:40:34 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277767#Comment_277767 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277767#Comment_277767 Tue, 07 Jan 2020 15:10:37 +0000 ajdunlop
We are going to make use of a small chimney breast that runs from the ground floor ceiling to the loft for extract ducts to get between floors and use the chimney stack for the exhaust. The chimney is small (about 455 x 470 mm), probably used for a kitchen stove, and is up my neighbours wall so is within the thermal envelope of the building, Any chimney breast that existed in the ground floor has been removed by the brickwork being stepped at ceiling height (think it was done at least 20 years ago).

The ducts are rigid 125mm spiral metal ducts. Two of these will go down the chimney from the unit in the attic to the ground floor kitchen ceiling. One will then go one way along the ceiling and the other the other way.
Diagram of this: https://www.icloud.com/iclouddrive/0ad5p_MnT8l3zc16PT58yCYsw#Bottom_of_chimney

I had been hoping to have the ducts go between the joists in the ceiling but had forgotten that there are short support joists either side of the chimney that go between the wall and the joist in front of the chimney to take the ends of the joist running parallel to the wall.

Plan diagram: https://www.icloud.com/iclouddrive/05WUJoYtjQrCcT3XctCmknL7w#Joists_around_chimney_2"
Dodgy Isometric diagram: https://www.icloud.com/iclouddrive/0Th6iJQd3G9hCsCQlwQwggykw#Joists_around_chimney"

What (if any) would be the best way to achieve this? What alternatives are there to support the joist closest to the wall that is broken by the chimney?

Thanks.]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277769#Comment_277769 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277769#Comment_277769 Tue, 07 Jan 2020 17:02:11 +0000 philedge Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277770#Comment_277770 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277770#Comment_277770 Tue, 07 Jan 2020 17:30:43 +0000 djh
Posted By: ajdunlopWhat alternatives are there to support the joist closest to the wall that is broken by the chimney?

Joist hanger?]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277778#Comment_277778 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277778#Comment_277778 Tue, 07 Jan 2020 21:24:31 +0000 ajdunlop
Hi @djh there should be a 'Download a Copy' button that will download the image files without having to log into / sign up to iCloud. If not let me know and I'll try to find somewhere else to put them.]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277780#Comment_277780 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277780#Comment_277780 Tue, 07 Jan 2020 21:28:56 +0000 ajdunlop Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277782#Comment_277782 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277782#Comment_277782 Tue, 07 Jan 2020 22:57:54 +0000 djh Posted By: ajdunlopHi @djh there should be a 'Download a Copy' button that will download the image files
Ah, yes. It wasn't working for me earlier but is now; still very slow. Ta.

@djh Are you suggesting using a joist hanger in the wall beside the joists with the gap for the chimney? Is there a special sort of hanger for this as I imagine the forces are a bit different to hanging the end of a joist?

I was thinking of suspending a joist hanger from the chimney. If that won't work then I'd suggest some custom metalwork to substitute for the stud joist, with a hole for the duct to pass through. A local metal shop should be able to knock a pair up for a few pounds. (Unless there is indeed a special type of joist hanger)]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277783#Comment_277783 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277783#Comment_277783 Tue, 07 Jan 2020 23:00:58 +0000 philedge
You might need to drill and tap fixings for floor boards or if theres enough room bolt a batten to the trimmer between the trimmer and the chimney.]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277796#Comment_277796 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277796#Comment_277796 Wed, 08 Jan 2020 12:44:46 +0000 ajdunlop
I like the idea of hanging off the chimney for simplicity except that there would be a large gap between the end of the joist to be supported and the chimney. Also as the chimney itself is not being supported I don't know if adding more weight would be a good idea.

Given you are both talking about fabricated metal replacements for the trimmers I think we are probably going beyond what I would be happy doing as a DIYer so I might have to think about solutions that don't interfere with the joists (boxing) or get a professional in to do the job. But thanks to your replies I have an idea of what sort of approach to expect someone I pay to do it.]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277801#Comment_277801 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277801#Comment_277801 Wed, 08 Jan 2020 13:40:24 +0000 djh Posted By: ajdunlopGiven you are both talking about fabricated metal replacements for the trimmers I think we are probably going beyond what I would be happy doing as a DIYer
You'll want to get a metalworking shop to make the pieces. It may be they can supply the expertise to measure and specify them too; otherwise you'll probably need to find a structural engineer.]]> Joists around chimney http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277831#Comment_277831 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16387&Focus=277831#Comment_277831 Thu, 09 Jan 2020 00:03:10 +0000 gyrogear (If no wall plate, maybe easiest to use a strongback on the floor-above).

For the hanger, you can fabricate it yourself from either threaded bar, nuts, washers and a metal crosspiece, or from bashing flat a length or two of drywall stud track, with appropriate holes to take suitable nails.
(I have used both of the above to effect).

Then remove the timmers.

Once you've got the ducts in, fabricate a liner around them (such as hollow clay pantiles..) then I'd fill in the floor void with lightweight keyed-in (reinforced) concrete, period.

IANASE (I am not a structural engineer).

gg]]>