G and J Posted June 15 Share Posted June 15 Peeps talk about a service void behind plasterboard being 25mm or 50mm. If it’s only for cables, almost all maximum 2.5mm2 FT&E, is there any reason that void couldn’t be smaller? Say 11mm? Link to comment Share on other sites More sharing options...
Mr Punter Posted June 15 Share Posted June 15 (edited) Ignore as I noticed this is for timber frame Edited June 15 by Mr Punter just noticed it was for timber frame... Link to comment Share on other sites More sharing options...
Kelvin Posted June 15 Share Posted June 15 (edited) You’ve got to fit the back boxes and 25mm plus plasterboard is as shallow as you can practically go really. There are 16mm back boxes but fitting all the cables in can be a challenge sometimes. You might also have the odd pipe in the void although I’d try and not do that. Edited June 15 by Kelvin Link to comment Share on other sites More sharing options...
jayc89 Posted June 15 Share Posted June 15 25mm void + your PB (min. 12.5mm) and use 35mm back boxes. Link to comment Share on other sites More sharing options...
JohnMo Posted June 15 Share Posted June 15 2 hours ago, G and J said: Say 11mm? We struggled in some areas due to the amount of cables, we had 50mm everywhere. Any smaller than 25mm will be splitting as you fix them. 50mm or 11mm isn't going to make the room feel any bigger or smaller Link to comment Share on other sites More sharing options...
G and J Posted June 15 Author Share Posted June 15 My word I’m such a bonehead. My head is so full of stuff explaining myself isn’t easy sometimes, there are so many disparate thoughts jostling to get to the front of the queue. The plan is to have an OSB or ply skin behind the plasterboard. This is personal preference (read OCD inspired folly, perhaps) but I like the idea of really solid walls I can hang stuff from anywhere, and maybe with better acoustic attenuation too. But I hadn’t thought about back box depth. 12.5mm PB, then 11mm OSB, then 11mm void = tight. OK, time to research back boxes….. And I have an ‘every millimetre counts’ attitude. The plot is 24’ wide, the house, externally, will be 21’. So to me and our already advanced layouts based on 1’ thick walls, it will make a difference. Link to comment Share on other sites More sharing options...
Kelvin Posted June 15 Share Posted June 15 You could plan to have no sockets or light switches on the external walls. If I look around my house I could easily have organised it to avoid sockets on the external walls for example. I only have two light switches on external walls. Link to comment Share on other sites More sharing options...
G and J Posted June 15 Author Share Posted June 15 45 minutes ago, Kelvin said: You could plan to have no sockets or light switches on the external walls. If I look around my house I could easily have organised it to avoid sockets on the external walls for example. I only have two light switches on external walls. Good thought. In fact that will be the case in some rooms, especially bathrooms. But our big downstairs everything room thingy (I call it The Great Hall as I do enjoy irony) will need stuff both sides. Link to comment Share on other sites More sharing options...
Kelvin Posted June 15 Share Posted June 15 If you can’t avoid sockets on the external walls then there’s not much you can do other than fit surface mounted sockets. For light switches then a bit of technology could sort that with wireless switches. Link to comment Share on other sites More sharing options...
G and J Posted June 15 Author Share Posted June 15 2 hours ago, G and J said: My word I’m such a bonehead. My head is so full of stuff explaining myself isn’t easy sometimes, there are so many disparate thoughts jostling to get to the front of the queue. The plan is to have an OSB or ply skin behind the plasterboard. This is personal preference (read OCD inspired folly, perhaps) but I like the idea of really solid walls I can hang stuff from anywhere, and maybe with better acoustic attenuation too. But I hadn’t thought about back box depth. 12.5mm PB, then 11mm OSB, then 11mm void = tight. OK, time to research back boxes….. And I have an ‘every millimetre counts’ attitude. The plot is 24’ wide, the house, externally, will be 21’. So to me and our already advanced layouts based on 1’ thick walls, it will make a difference. Bingo! https://www.ukelectricalsupplies.com/norslo-dry-lining-box-2-gang-32mm.htm Link to comment Share on other sites More sharing options...
JohnMo Posted June 15 Share Posted June 15 17 minutes ago, G and J said: Bingo! https://www.ukelectricalsupplies.com/norslo-dry-lining-box-2-gang-32mm.htm Bingo - not The 35mm refers to the depth of the box, the issue is the 35mm box is good for up to 16mm wall thickness you are wanting nearer to 25mm (with plaster), so then you need the deeper 47mm back box, but not all of them are suitable either Link to comment Share on other sites More sharing options...
G and J Posted June 15 Author Share Posted June 15 49 minutes ago, JohnMo said: Bingo - not The 35mm refers to the depth of the box, the issue is the 35mm box is good for up to 16mm wall thickness you are wanting nearer to 25mm (with plaster), so then you need the deeper 47mm back box, but not all of them are suitable either Ah. So I have to oversize the hole in the OSB/ply. I think. Link to comment Share on other sites More sharing options...
JohnMo Posted June 15 Share Posted June 15 Just now, G and J said: Ah. So I have to oversize the hole in the OSB/ply. I think. That would work. Good thinking. Link to comment Share on other sites More sharing options...
G and J Posted June 15 Author Share Posted June 15 Do peeps generally fit the backboxes before plastering like with solid walls? I’ve only ever retrofitted to plastered stud walls…. Link to comment Share on other sites More sharing options...
markocosic Posted June 16 Share Posted June 16 What is the frame construction? If you only have a membrane between insulation and service cavity, and you only fit sockets in the centre of a 600 stud bay, you can go deeper and flex the membrane slightly (say 10mm) IMO yes back boxes before plastering. Use blanks to stop em getting filled with plaster. e.g. https://www.ebay.co.uk/itm/145306620788 Oversize cuts in OSB work for the "wings" of a back box. Some spray foam as glue between the layers increases strength. You'll still need reinforcing for material loads. Do try to plan ahead. Link to comment Share on other sites More sharing options...
Kelvin Posted June 16 Share Posted June 16 12 hours ago, G and J said: Do peeps generally fit the backboxes before plastering like with solid walls? I’ve only ever retrofitted to plastered stud walls…. You can do it either way. Easier for the plasterer if they are fitted afterwards plus the boxes don’t end up full of plaster. Slightly harder to cut the boxes and there’s the danger of the plaster chipping off around the box cuts. Link to comment Share on other sites More sharing options...
G and J Posted June 16 Author Share Posted June 16 3 hours ago, markocosic said: What is the frame construction? If you only have a membrane between insulation and service cavity, and you only fit sockets in the centre of a 600 stud bay, you can go deeper and flex the membrane slightly (say 10mm) IMO yes back boxes before plastering. Use blanks to stop em getting filled with plaster. e.g. https://www.ebay.co.uk/itm/145306620788 Oversize cuts in OSB work for the "wings" of a back box. Some spray foam as glue between the layers increases strength. You'll still need reinforcing for material loads. Do try to plan ahead. Those protectors are great, thank you. I’d not be confident about stretching the membrane - I’d worry that thermal cycling would maybe wear holes, but I think the plan works without that. Link to comment Share on other sites More sharing options...
G and J Posted June 16 Author Share Posted June 16 3 hours ago, Kelvin said: You can do it either way. Easier for the plasterer if they are fitted afterwards plus the boxes don’t end up full of plaster. Slightly harder to cut the boxes and there’s the danger of the plaster chipping off around the box cuts. We’re likely to end up with trendy thin metal switches and sockets so they won’t hide what is in effect a surface mount rim on the dry lining box, so I think plastered in is definitively the best way for me. Link to comment Share on other sites More sharing options...
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