Best way to cut out block work to fit a deep back box?

[wywywywy]

Hi all,

Basically I would like to fit an in-wall iPod dock, which needs around 80mm of clearance behind the plasterboard. However, I only have around 25mm between the plasterboard and the block work.

So, what is the best way to take a chunk out of the block work in order to fit a deep back box? I did think about drilling a series of holes and then chiselling it out, but that would take forever!

Thanks.

 

[riveralt]

How thick is your wall? I think there are Building regs regarding how deep you can chase.

 

[ban-all-sheds]

I did think about drilling a series of holes and then chiselling it out, but that would take forever!

You'd better start now, then....

 

[Richard C]

I did think about drilling a series of holes and then chiselling it out, but that would take forever!

I always do them like that. Piece of tape around an 8mm drill bit as a depth gauge; drill around the perimeter & across the centre, plug usually comes out in 2 lumps. Straighten out the sides with a 3” bolster chisel, perfect fit, doesn’t take long at all. I’ve even done them in brick but that is harder work & does take longer.

 

[riveralt]

I did think about drilling a series of holes and then chiselling it out, but that would take forever!

I always do them like that. Piece of tape around an 8mm drill bit as a depth gauge; drill around the perimeter & across the centre, plug usually comes out in 2 lumps. Straighten out the sides with a 3” bolster chisel, perfect fit, doesn’t take long at all. I’ve even done them in brick but that is harder work & does take longer.

Do you know I learn something new every day, I didn't realise there were electricians who specialise in fitting an inwall Ipod dock?- Does it pay much?

 

[Richard C]

Do you know I learn something new every day, I didn't realise there were electricians who specialise in fitting an inwall Ipod dock?- Does it pay much?

Didn’t say I was a spark, although I do install where permissable or under supervision. I just fit all my own back boxes in connection with renovation work I do. Ipod dock, electrical back boxes, what’s the difference; principle is the same although 55mm is pushing it a bit!

 

[riveralt]

Didn’t say I was a spark, although I do install where permissable or under supervision. I just fit all my own back boxes in connection with renovation work I do. Ipod dock, electrical back boxes, what’s the difference; principle is the same although 55mm is pushing it a bit!

That was my concern, which is why I asked the OP about the thickness of his wall. I'm sure there is a Building Regulation that gives the max sizes of chase depths and chase widths - not sure how big an ipod dock is and having seen a picture of one - got to ask the question why?

 

[Richard C]

That was my concern, which is why I asked the OP about the thickness of his wall. I'm sure there is a Building Regulation that gives the max sizes of chase depths and chase widths - not sure how big an ipod dock is and having seen a picture of one - got to ask the question why?

I’m not sure how big an Ipod back box is either but it’s just a hole. As long he doesn’t go through the other side & no cavity is breached, it’s not going to have any structural effect or break any B Regs as far as I’m aware; no different to cutting a hole in a wall for, say, a fan duct or boiler vent. If the OP was cutting a cable chase 55+mm deep then I would be concerned; FYI maximum depth of chasses is 1/3rd of the wall thickness for vertical; 1/6th of the depth for horizontal.

 

[wywywywy]

Hi,


Thanks for the answers.

It will need an American size double-gang back box, which is bigger in size than a UK double gang back box but not really by that much. As for thickness, it is just standard single block - this is a support wall between the kitchen and the living room, not an external wall, so there is no cavity, damp proofing, insulation, etc to think about.

riveralt - There are lots of people (AV Integrators) who fit in-wall iPod docks, plasmas mounts, hidden projectors, home automation equipments, whole house audio systems, etc for a living. And yes they do make a good living. But it is not just fitting them, there is also programming them.

Cables are already in place sandwiched between the plasterboard and the block word by the way.

So am I still okay cut a hole? If so I think I need a better drill and chisel...

This is a link to the dock -
http://www.sonance.com/products/legacy/detail/123

Thanks.

 

[Monkeh]

It's doable, but tight. You need to be very, very careful about your drill depth, and if I were you I'd use a cold chisel and a lump hammer rather than an SDS chisel to remove the bulk. You don't want to punch a hole through..

 

[Lectrician]

Didn’t say I was a spark, although I do install where permissable or under supervision. I just fit all my own back boxes in connection with renovation work I do. Ipod dock, electrical back boxes, what’s the difference; principle is the same although 55mm is pushing it a bit!

That was my concern, which is why I asked the OP about the thickness of his wall. I'm sure there is a Building Regulation that gives the max sizes of chase depths and chase widths - not sure how big an ipod dock is and having seen a picture of one - got to ask the question why?

Think about it guys - a 55mm deep small square hole? How is this different from a 4 or 6 inch fan hole THROUGH a wall? You are alarming the guy for no reason at all! A 50mm deep horizontal chase would be a different matter.

 

[Richard C]

So am I still okay cut a hole?

I see no problem at all. Use a hammer & cold chisel as suggested not an SDS; take it steady or you could crack the plaster on the other side of the wall. As it’s double box size, drill 2 lots of vertical holes to divide up the baulk into 3, it’ll come out far easier.

Think about it guys - a 55mm deep small square hole? How is this different from a 4 or 6 inch fan hole THROUGH a wall? You are alarming the guy for no reason at all! A 50mm deep horizontal chase would be a different matter.

Alarming the OP ; read my subsequent post, nothing in there to alarm the OP, if fact you’ve more or less repeated what I said.

As long he doesn’t go through the other side & no cavity is breached, it’s not going to have any structural effect or break any B Regs as far as I’m aware; no different to cutting a hole in a wall for, say, a fan duct or boiler vent. If the OP was cutting a cable chase 55+mm deep then I would be concerned; FYI maximum depth of chasses is 1/3rd of the wall thickness for vertical; 1/6th of the depth for horizontal.

 

[ban-all-sheds]

Maybe best not to try and cut a hole for this dock though...