Replacing pattress boxes.

[GagsPritch]

Recently my wife asked me to replace all the mounting boxes in our house. They're all pretty old and it seemed like a good idea. I bought new boxes for all the sockets and light switches in the house and although I'm not an electrician I did go to college to do level 2 electrical installations so thought this would be easy. It turns out that all the premade holes in the new boxes are in  different positions to the old boxes. So it's not just a case of removing the old ones and screwing in the new ones. I'd have to drill new holes for every single one. The thing is when I started drilling all the plaster started breaking away in big pieces. I guess my question is can I just fill in the cavity with filler and screw straight into that? What would an electrician do in this situation?

Thanks in advance 

[ProDave]

Unless the back boxes are rusted, threads stripped, or some other damage, an electrician would do nothing.

 

It seems a strange idea to change something you should not ever see when the fitting is in place.  

 

Photos might explain the why?

 

 

[JohnMo]

10 hours ago, GagsPritch said:

Recently my wife asked me to replace all the mounting boxes in our house.

If they are an issue, I would be more concerned that the wiring is an issue also. Are you sure you didn't miss hear her? What prompted the request?

[Super_Paulie]

the most bizarre request ive ever heard i think. Not like you're showing them off to visitors.

[Tom]

48 minutes ago, ProDave said:

It seems a strange idea to change something you should not ever see when the fitting is in place.  

I guess they're surface mounted?

[sgt_woulds]

Old ones won't have bonding connecteions for metal face plates, but those can be soldered on without removing from the wall. 

 

Other than that, as long as they are deep enough to take the gubbins for modern sockets without crushing cables I can't think of a reason to replace them?  

[sgt_woulds]

GagsPritch, are you talking about surface mounted plastic pattress rather than metal back boxes sunk into the wall?

[GagsPritch]

Sorry I should have clarified. These are plastic surface mounted pattress boxes. They're all visible and have gone to look yellow.

[Crofter]

It would be easier to drill new holes in the plastic boxes than to drill new holes in the wall, by the sound of things.

[garrymartin]

Have you looked at different brands of pattress boxes? Perhaps another brand has the same layout holes?

[ProDave]

Can you post pictures of one of the old ones with dimensions of what you are trying to match?

 

Alternatively buy one of these and see if you can accept the look, if you can, these are a softer plastic that you can drill to match the holes of the old box.

 

https://www.screwfix.com/p/deta-tte-2-gang-surface-pattress-box-32mm/437vt

 

[GagsPritch]

I tried drilling new holes in the new boxes and managed it with 1 of them but 3 others just shattered. I didn't know you could get some with softer plastic, I'll look into that thanks. Might heat up a nail and try melting a new hole too.

[ProDave]

Most boxes are just too hard and brittle to drill.

 

You can cut them with an Abra file in a hacksaw blade, but you have to start at an existing hole and cut from there.

[Mr Punter]

Have a look at D-Line.  They claim to be softer material and may work for you.  https://www.screwfix.com/p/d-line-tsb35w-2-2-gang-surface-pattress-box-35mm-2-pack/143cy#product_additional_details_container

[Onoff]

On 03/12/2025 at 10:02, sgt_woulds said:

Old ones won't have bonding connecteions for metal face plates, but those can be soldered on without removing from the wall. 

 

Other than that, as long as they are deep enough to take the gubbins for modern sockets without crushing cables I can't think of a reason to replace them?  

 

Not what the OP is talking about as he's confirmed above.

 

Again an aside to the thread but on the subject of back box earth terminals, where I've come across the odd one that's damaged I've drilled and fitted a Rivnut and ring crimp

 

Broken screw:

 

 

Rivnut tool:

 

 

New earth termination vs old:

 

 

Rivnut shown here on a loose back box just for clarity: