Lowering ceiling by 100mm?

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I’m getting the wood for this on Saturday.

I was thinking of using 3x2 and fixing a 6”ish piece to the existing joists with a couple of screws then going under that with a full piece a bit like this (not to scale):

8FE517B3-ED87-486D-AB36-859025CF5D9C.jpeg



What’s the difference between 3x2 CLS and normal 3x2?
 
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I did one of my bedrooms with 100mm celotex and plasterboard under, hard work and the long screws were quite expensive. I did second bedroom with 50mm insulated plasterboard (only because I got some dirt cheap). New ceiling heights are 2.4 and 2.45 - both fine. I also have 200mm of mineral wool above. I took a gamble on it all being effective and replaced the big old rads with new ones half the output - they've been fine, we have an upstairs heating zone and it barely needs to be on. I think it's particularly effective because it eliminates the gaps/cold bridging etc and properly covers the perimeter where most heat is lost - conventional loft insulation tends to be lacking at the eaves.
 
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Ok, I need some help because I think my method is ****e.

Couple of pics:
D6AB15BC-3B9A-4CE8-9E36-03E552AECD21.jpeg

873E5BA9-C65B-4753-BD19-327931C2CA40.jpeg

2FD738E6-B651-479D-9136-23C1200372DD.jpeg



I’ve put a 4x2 block on each existing joist and then attached my new lower 3x2 to that. Problem is, it’s taking ages and I think the ceiling bananas a bit.

Instead I’m thinking of screwing a full length of 3x2 to the existing rafters each side of the room, so just 2 pieces. Fixing my new lower 3x2’s onto them and then adding a couple of straps along their lengths to the existing rafters through a small hole in the lath and plaster ceiling.

Realistically, how far can I span between fixings using 3x2 scant?

Thanks :)
 
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So the existing ceilings are like a banana, you can’t tell by looking but as soon as I offer the new ceiling joists up it becomes clear.
 
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How easy is it to get to the roof space?

Why don’t you punch through the ceiling ever few joists and screw some 3x2 into the sides of the joist and dropping down into the room.

Get your string line and cut them all level and fix you 3x2 lengths to that....almost the way you’d put post joists in for decking but upsidedown.
 
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It can be a bit of a faff first time, but in this instance, time well spent.
A perfect ceiling once set up.


I’m just reading Freddie’s link now.

I’m thinking I’d struggle with the perimeter because the 2 internal walls are those hollow terracotta blocks which are really weak and the 2 external walls have the angle on them. I want to stay close to that angle so I don’t loose too much head height.

Then if I hang the rest off the already sagging ceiling would it be prone to cracking? By fixing the timber across the existing joists I feel like I’m making them stronger.

Right now I’m wondering if I could drop the ceiling and add new 6x2 joists fixed to the rafters where I marked in red on this image I googled of a similar ceiling. That way I have a single, very strong ceiling and she make better use of the loft.
161EA14E-FA42-42CB-BE67-B09881EC7A42.jpeg
 
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How easy is it to get to the roof space?

Why don’t you punch through the ceiling ever few joists and screw some 3x2 into the sides of the joist and dropping down into the room.

Get your string line and cut them all level and fix you 3x2 lengths to that....almost the way you’d put post joists in for decking but upsidedown.

That’s close to what I thought when I said about fixing a single 3x2 down each side then hanging the others off straps.
 
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Ah yes, sorry didn’t spot that bit. That’s what I’d do personally.

I’ve got it in my head to rip it all out now.

The wall between the 2 bedrooms is made of those hollow blocks and is built up off the floorboards an inch away from a huge joist. If I built a structural stud wall off that joist to the same height as the wall plate, I could span 8x2 between the two, fix it to the rafters and I (really my daughter) would have perfectly flat strong ceilings, a better wall, decent loft storage... better all round.
 
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Sounds like a good plan, but a lot of work a mess there. I guess as long as your daughter is planning on staying in the house for a while it’s worth the extra effort (y)
 
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That's pretty much what I did, nice flat ceilings, loft storage and room for insulation:
IMG_20180201_154734183.jpg


I do wonder if those terracotta walls have any structural strength? I had one between this bedroom and the bathroom next door, it literally fell apart when I stripped the plaster off it so I replaced it with a stud wall, I think because they are so light they don't "settle" over the years like a heavy old brick wall when the joists deflect, they just crack. I also never understood why they built the walls off the floorboards between joists but it's to spread the load between adjacent joists.
 

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