metal back boxes too deep in wall

[lilman]

Installed metal back boxes and cabling into walls of outhouse conversion - went back today and customer has increased depth of celotex on walls to 100mm (was 25mm)! All boarded and skimmed. I had to cut board to find outlets. Issue is - I can't bring back boxes forward as I can't get behind them. I could use long screws to fit socket fronts to existing back boxes and all will look fine, but this will leave an area behind each socket that is not enclosed within the back box. What are my options? Cheers all.

 

[Zeespark]

Replace the 25mm backboxes with 47mm ones?

AndyGuinness

 

[lilman]

Replace the 25mm backboxes with 47mm ones?AndyGuinness

Still leaves a gap of about 50mm - also I can't feed the cables into replacement back boxes without destroying the new plastering.

 

[Zeespark]

What about using 47mm boxes and some extension boxes?

AndyGuinness

 

[lilman]

What about using 47mm boxes and some extension boxes?AndyGuinness

Metal extension boxes? Got a link?

 

[Ste Mac]

You could stack a couple of these

http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/261020.xml

 

[Riggy]

I'd ignore the old boxes, fit drywall boxes and bring the cables into them through the back.

 

[Evans Electric]

If there is a solid surface to the cellotex can you fit a Fastafix box and ignore the KO box. ??

Or as Zeebrugge says use extension KO box doo-dahs .

I was caught out with that stuff , they have to fix it on outside walls on refurbs I believe.

 

[monkey5]

drylining boxes?

not sure what celotex is, is it like kingspan, then boarded over?

 

[steptoe]

or you could stop worrying too much and just use extension studs!

 

[Barx]

Isnt celotex generally polystyrene. If so, make sure your cables aren't touching it as over time it will cause trouble.

 

[Riggy]

Isnt celotex generally polystyrene. If so, make sure your cables aren't touching it as over time it will cause trouble.

What sort of trouble?

 

[lilman]

or you could stop worrying too much and just use extension studs!

Wouldn't normally worry - NICEIC area engineer coming for a look though. Typical.

 

[Barx]

it leeches the polymers out of the PVC, these are what makes the PVC flexible. Eventually it goes brittle and breaks down somewhat.

 

[Evans Electric]

Migration of polymers I believe . Thats if it is polystyrene , no idea what its made from.

 

[PC Electrics]

Celotex and Kingspan are trade names for much the same stuff. Not polystyrene afaik.

Riggy beat me to the dry lining box suggestion.

 

[Evans Electric]

Wouldn't normally worry - NICEIC area engineer coming for a look though. Typical.

They used to love catching you out with boxes too far back .

One reckoned the cut edge of plasterboard within a KO box was a fire hazard . Insisted that boxes were brought level with front of the board .

 

[lilman]

drylining boxes?not sure what celotex is, is it like kingspan, then boarded over?

If you really want to know what Celotex is - What is Celotex? - Celotex Home Insulation

 

[VoltzElectrical]

Kingspan and celotex are not polystyrene. So don't worry. Extension boxes are best bet, or fast fix boxes. Biggest worry is cables still long enough!

 

[Hayeso32]

Go for the metal extension boxes, you can get them in different depths!