Metal boxes?

[winger1979]

Hi
I am replacing some double plug sockets in a garage renovation. I now have single skin with batten and plasterboard. Total of 62mm from front of board to brick. Are dry lining or metal boxes best ? Also when to install before or after plasterboard goes up ?
Thanks

 

[phatboy]

Well you cannot install dry lining boxes before the dry lining!

The box type is down to your preference - dry lining boxes will leave a nice space so wont bridge to the single skin blocks. If you use metal you can mount a crossbeam to the studs either side, but make sure they are away from the blockwork, so they don't allow water to bridge to the electrics.

 

[ban-all-sheds]

I now have single skin with batten and plasterboard.

Any insulation? What will the space be used for? Will it be heated?

 

[winger1979]

Yes 50mm insulation in there. Bit concerned whether drylining boxes will be strong enough for double gang sockets

 

[Lectrician]

I am not a fan of dry liners where you can fit metal boxes at first fix stage.

Have you got a damp proof membrane over the external skin, and then stud work in front? If your construction is done correctly, there is no issue with rusting boxes.

 

[davelx]

I am not a fan of dry liners where you can fit metal boxes at first fix stage.

Have you got a damp proof membrane over the external skin, and then stud work in front? If your construction is done correctly, there is no issue with rusting boxes.

AIUI, unless you are using impermeable insulation, the vapour barrier has to be on the warm side - ie the inside of the insulation, otherwise you get warm moist air going through the insulation and meeting a cold vapour barrier, resulting in condensation. Where you cut out for the back boxes you have to seal with tape.

With impermeable insulation, joints/edges need to be sealed to the studs on the inside for the same reason.

 

[Lectrician]

The outer wall needs a damp proof membrane, there should also (or could also?) be a vapour barrier behind the plasterboard, or foil backed plasterboard used.

When I converted half my garage into a utility room, I had to put a damp proof membrane on the outer wall, stud off with 3" timber, without fixing to outer skin, insulate with 75mm insulation, then vapour barrier, then insulation backed plasterboard.

The floor was raised and ventilated, and damp though the wall would track down the damp proof membrane and under the floor to the concrete over site, where it was ventilated.

This is what BCO instructed me to do.

 

[winger1979]

I was advised membrane next to internal wall and that's what I have gone with . Decided to go with fixing metal boxes thanks for help

 

[ban-all-sheds]

I was advised membrane next to internal wall and that's what I have gone with.

Is that all?

No vapour barrier on the warm side of the insulation?

 

[winger1979]

No apparently not as the moisture gets trapped .

 

[knowall]

Metal boxes ? on the hillside , no seriously - fast fix, is best no rust or additional fixings required. Just fit them nice and snug!

KA

 

[ban-all-sheds]

No apparently not as the moisture gets trapped .

Without one warm air will get to the cold side of the insulation, and condense on the walls.