Metal clad or recessed sockets for garage?

[aa44]

I am just about to start building my new house, starting with the (attached) garage. I would like people's opinion on what socket type to put in the garage.

The house will be built using ICF (insulated concrete formwork - like polystyrene lego with concrete in the middle). The inside of the garage will have plasterboard fixed on top of the polystyrene and then plywood up to a height of 1.2m to protect against knocks. As the plywood will cover from floor level to 1.2m, I would like to fix the sockets to the plywood. Rather than run the cables in conduit on the surface of the wall, I can easily run the cables in conduit in the polystyrene behind the plasterboard. (This is how it will be done in the rest of the house).

Given that I can bury the cables in the wall, am I better off going for a flush mounted box and a standard white plastic socket? If so, what sort of box should I go for? Should I just go for a standard dry-lining box and clamp it around the plywood rather than the plasterboard?

I like the robustness of metalclad sockets but I would need them with knockouts at the back of the backbox and as far as I can see only MK (expensive!) do them.

Anyone got any ideas?

 

[Monkeh]

That had better be thick, well supported ply if you want that garage to survive..

Nonetheless, you can use any metalclad faceplate with a normal, metal flush box and just discard the surface box. A dry lining box won't allow for (side) conduit entry.

 

[ELZ4742]

re. metal clad socket

a 20mm hole cut in the back box with a gromit or female adaptor perhapes?

edit.. oops..thought you doing surface

 

[aa44]

Thanks for that Monkeh. I am reluctant to use metal flush boxes as I don't have anything solid directly behind the box to attach it to. From the surface it will be 12mm ply, 12.5mm plasterboard, 67mm polystyrene, 150mm concrete. Assuming that I used 45mm deep boxes, then I would need to cut out 21mm of the polystyrene but would still have about 45mm of polystyrene between the back of the box and the concrete. That is why I was thinking of using the drylining boxes.

 

[aa44]

re. metal clad socket

a 20mm hole cut in the back box with a gromit or female adaptor perhapes?

edit.. oops..thought you doing surface

I am happy to use surface mounted metalclad boxes, I am just worried that the only ones with knockouts in the back are the MK ones and MK surface mounted 2 gang sockets seem to cost about a tenner when the cheaper ones are about a fiver.

 

[Monkeh]

Is there not going to be a timber frame for the plasterboard to sit on?

 

[Monkeh]

re. metal clad socket

a 20mm hole cut in the back box with a gromit or female adaptor perhapes?

edit.. oops..thought you doing surface

I am happy to use surface mounted metalclad boxes, I am just worried that the only ones with knockouts in the back are the MK ones and MK surface mounted 2 gang sockets seem to cost about a tenner when the cheaper ones are about a fiver.

You get what you pay for. And you don't need a knockout in the back, which is what he's suggesting. You can easily make your own hole with a 20mm holesaw or sheet punch (neither of which is shockingly expensive, and both of which should be in the toolbox of your electrician).

 

[ELZ4742]

no reason why you cannot cut a 20mm hole in the back of a cheaper box as long as you protect the cables with a gromit conduit adaptor etc..

 

[aa44]

Is there not going to be a timber frame for the plasterboard to sit on?

No. The ICF system contains a series of polypropylene webs at 8 inch centres. These run right through the ICF polystyrene / concrete / polystyrene sandwich and provide secure fixing points for most things. The plasterboard is simply screwed to these webs and the plywood will be screwed through the plasterboard to the webs.

 

[Monkeh]

Is there not going to be a timber frame for the plasterboard to sit on?

No. The ICF system contains a series of polypropylene webs at 8 inch centres. These run right through the ICF polystyrene / concrete / polystyrene sandwich and provide secure fixing points for most things. The plasterboard is simply screwed to these webs and the plywood will be screwed through the plasterboard to the webs.

Most things.. including a bit of timber to fix backboxes to?

 

[ELZ4742]

can you not cut in metal knock out boxes and screw the sides into the side of the ply?

 

[RF Lighting]

can you not cut in metal knock out boxes and screw the sides into the side of the ply?

 

[aa44]

Is there not going to be a timber frame for the plasterboard to sit on?

No. The ICF system contains a series of polypropylene webs at 8 inch centres. These run right through the ICF polystyrene / concrete / polystyrene sandwich and provide secure fixing points for most things. The plasterboard is simply screwed to these webs and the plywood will be screwed through the plasterboard to the webs.

Most things.. including a bit of timber to fix backboxes to?

Not really. The ICF form looks like this.

http://www.nudura.com/EN/icfproducttechnology.aspx

The plastic webs end with a flat piece just under the surface of the polystyrene and so provide a fixing point for things being attached to the surface of the polystyrene (e.g. plasterboard). In my case, the back face of the box will be inside the form behind the attachment point of the web. Attaching a piece of timber to the webs is a common way of doing things such as providing fixing areas for kitchen cupboards but I don't think will work in my case.

The idea of attaching metal flush boxes through the sides into the edge of the ply sounds like a plan.

 

[Monkeh]

Another option would be a simple piece of 2x3 behind the box, fixed into the concrete. Certainly I wouldn't try fixing the box into 12mm ply: The stuff is far to thin for a screw into the edge, and even if you managed it it'd tear right off if pushed. You'd also have problems getting conduit to the side entries on the box.

 

[sparkwright]

am I better off going for a flush mounted box and a standard white plastic socket?

You can still have standard size metal sockets to go on your flush mounted boxes, remember.