Depth of chases and knock out boxes

[soms]

Hi, I would be interested to hear the opinion of the seasoned/experienced members on the following:

Approved Document A tells us the maximum depth of vertical and horizontal chases in walls and that chases should not impair the stability of the wall in order to comply with Part A of Schedule 1 of the Building Regulations as they apply in England.

My question is, do the depths apply to recesses made for back boxes, or just for channels created for cables?
Clearly is would be desirable that any recesses for back boxes would not want to impair the stability of the wall.

In a text book I have somewhere there is a diagram of this for the horizontal and vertical chases and it does not show it applying to the back box/knock out box.

Thank you in advance for any advice.

 

[SparkyChick]

I think the reason they talk about chases is simply because of their size relative to the wall. It's not impossible to imagine a scenario where a chase runs the length of an entire wall.

If it's too deep, you've compromised the entire length of the wall and subject to the inevitable structural movement, the stresses could see a failure along the chase.

In the case of a back box, if it's in block work, you've got quite a substantial area around the box that is still complete and capable of taking the load. In bricks, I would say it depends on the integrity of the mortar. If it's crappy lime cement and it's falling apart, I'd be a bit loathed to cut a big chunk out for a back box.... that said, it's not uncommon in my experience to see blocks move in modern houses when you're cutting a section out for a back box.

 

[telectrix]

also bear inmind that cable chases are generally onl plaster depth, so do't compromise the structure in any way. it's only when you get into the brick/block that you need to be concerned. very rate these days to see a wall plastered. usually dot&dab, applied by monkeys.

 

[soms]

Thank you for your sharing your thoughts, I will bear that in mind.
It occured to me as I was writing a little blurb about complying with Building Regulations for my NVQ portfolio.

 

[telectrix]

Thank you for your sharing your thoughts, I will bear that in mind.
It occured to me as I was writing a little blurb about complying with Building Regulations for my NVQ portfolio.

wait till you come across straw walls. .

 

[Pete999]

Hi, I would be interested to hear the opinion of the seasoned/experienced members on the following:

Approved Document A tells us the maximum depth of vertical and horizontal chases in walls and that chases should not impair the stability of the wall in order to comply with Part A of Schedule 1 of the Building Regulations as they apply in England.

My question is, do the depths apply to recesses made for back boxes, or just for channels created for cables?
Clearly is would be desirable that any recesses for back boxes would not want to impair the stability of the wall.

In a text book I have somewhere there is a diagram of this for the horizontal and vertical chases and it does not show it applying to the back box/knock out box.

Thank you in advance for any advice.

View attachment 42315

Chop it out as you wish, put your cables boxes, whatever in, fill with compe, probably stronger than the crap they build houses with these days anyway.

 

[gazdkw82]

Another thing to consider is the type wall you are chasing or putting back box into. For example, you wouldn't want to go very deep on an active chimney breast for obvious reasons.

Also what does everyone use to fill around back boxes?

 

[Pete999]

Another thing to consider is the type wall you are chasing or putting back box into. For example, you wouldn't want to go very deep on an active chimney breast for obvious reasons.

Also what does everyone use to fill around back boxes?

What on a new build or rewire?
New build Sand and cement, nick a bucketful from the Brickies, rewires depends Polyfilla or some other proprietry caulking.

 

[gazdkw82]

What on a new build or rewire?
New build Sand and cement, nick a bucketful from the Brickies, rewires depends Polyfilla or some other proprietry caulking.

I thought as much. Although these days new builds have more stud walls than brick walls.

 

[Paul.M]

wait till you come across straw walls. .

Tel, long time no speak

Straw walls!!!! Had this (again) earlier this year in a bungalow. Simple new kitchen install with a DB change + house renew of sockets and light fittings. Run the cable in the loft ready to drop down to kitchen points. Drilled hole in the wall and it was 12mm chip wood with straw insulation!!!!

Went through the options with the new home owner, pvc conduit + fire insulation for all the back boxes or get it ripped out and put in new plaster board and kingspan etc. A bit safer for a kitchen lol. It is a tinder box.

For the man that can afford £600 for a new TV, he cant afford the £400 for new plastered walls? He got "Dave from down the pub" to do the electrics because he thinks its fine. Crossing my fingers with that one.