Ceiling joist questions

[Wipster]

Hey all,
I'm a bit unsure of the terms so I will do my best to explain what I want to do. Maybe with a picture.

So I have recently taken out a chimney breast which was left hanging on the first floor, it was already removed bellow and on the roof, and wasn't supported. Fun.

Now I come to sort out the gap where it went through the ceiling, the hole spans 3 joists however only two where braced infront of the breast with the third resting on a shoulder. Now without the shoulder I have it acro'd up until its secured.
Measurements are joist to joist 300mm, un-cut joist length is 1.8m and size of proposed brace length would be 1200mm.
Above its only inaccessible loft space at that back of the house so it will only be supporting the old lath and plaster ceiling.

What I was planning was to cut the joist which rested on the shoulder shorter, remove the current brace and attach a longer one to bridge the gap. Would a length of 47x100 treated carcassing from TP do the job?

Cheers

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• Wipster
• 23 Jun 2013
• 1

 

[pinenot]

The first thing to say is that as the present arrangement has held up, as it were, within an unsupported chimney breast, why the need for accrows?

I assume from your pic that the two two joists either side of the original breast, are supported within the wall, that being the case simply cut off the third projecting joist in line with the two others build a box out of the same joist dims timber, to fit the space left. This would be best fixed to the wall with chemi anchors (assuming it's brick) to beef this section up, nail remainder all round, staggering up and down, then fit stub joists to match original. View media item 62939 ...pinenot

 

[Wipster]

Thanks for getting back to me so quickly
I put the accrows in to support the joist which was resting on the chimney shoulder, while the bottom of the chimney wasn't supported it was being held up by the keying bricks so was able to hold some load. Its possible to flex that section by pushing up so to be safe I put the support in.

So do you reccon leaving the old boxing in place and adding another piece to span the full width is the way I should go?
I'm not sure what chemi anchors are honestly and fitting stub joists?

Sorry for the questions heh
Thanks!

 

[pinenot]

(chemi anchors) chemical anchor bolts, are simply threaded rod/bolts hammered into drilled holes in the brickwork filled with a glass like tube filled with epoxy resin when the threaded rod/bolt is hammered in the tube breaks surrounding the bolt and filling the hole, whereupon it sets rock hard. This allows the timber trimmer against the wall to be fully anchored with nuts and spreading washers (sounds more complicated than it actually is) The first 30 sec or so of this video link, gives you a good idea of the process - https://www.youtube.com/watch?v=dzb3hjLJl80
Here's my dwg. showing the stub joists within the box frame, just short (stub) timbers same as the frame itself, it's best to fit these after the box frame has been fixed in place, both with the anchors and nails. This arrangement provides both rigidity and load bearing along with a continuity under the floor, same as the original...pinenot

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• pinenot
• 24 Jun 2013
• 1

 

[tony1851]

No need to faff about with chemical fixings or joist hangers.
The loads here are minimal so end-nailing would be OK.

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• tony1851
• 24 Jun 2013
• 1

 

[Wipster]

Awesome thanks for the help!
Got the materials this morning will crack on and get it fixed up tonight