chasing

sundula

how deep do chases for electrical sockets etc need to be in a new build?

Going to use 22mm flat wavin

sundula

anyone?

patrido

deep enough that the wavin and the clip is sunk below the level of the blocks. about 20mm iirc. make it easy for your plasterer to do a good job afterwards.

sundula

so if its flush with the wall it would be ok

Victor

Flush or about flush with the blockwork, the plasterer should be able to pick up some tolerence.

Remember, vertical only, no horizontal. And amke sure your postions are sufficiently far away from corners and openings in structural walls.

tcs

Victor - what's the thing with

vertical only, no horizontal

?

Saw this before on a thread on this forum. It may have been you who said it or maybe someone else...

Victor

tcs, might have been me

patrido wrote:

just wondering about your post where you said vertical only, never horizontal...

are you quoting the regulations, or just good practice?

I know it's best to always go vertical, but i thought the regulations said you could chase both vertically and horizontally as long as it is going direct to a switch/socket/etc??

Three things:

(a) Not only are you narrowing the thickness of the wall, you are also setting up cracks around the chase, weakening the wall further. While much of the time you will get away with it, doing it at critical points is compromising the whole wall.

Look at what blocklayers do to break blocks - they form a small chase and hammer the block - it quickly snaps in two (concrete is very good in compression but poor in tension).

If the wall is subject to an excessive load (storm, poor foundation, collision) its just going to snap.

(b) Doing it horizontally also reduces the load bearing cross-section area of the wall substantially compared to vertical chasing. A horizontal 20mm chase in a 100mm wall would reduce the load bearing cross-section area of the wall 20+%. Vertically, it would only reduce it by 20+% at that point

If you chase near junctions in structural walls, where those junctions have been deliberately bonded to each other to provide the building with rigidity, or around door and window opening, you are weaking the areas that get subjected to the highest loads (imagine a door being caught in a gale).

(c) Its a lot easier to find vertical chases because you can just look for the socket / fitting. If you have a cluster of fittings together it is usually more practical to do a very short horizontal chase, saving not just work, but also trauma to the wall.

patrido

ah, i thought you might be referring to electrical regulations.

my reading of the building regulations is that vertical chases are allowed to one third of the thickness of the wall, and horizontal chases allowed to one sixth of the thickness of the wall (approx 16mm in a 100mm block) and never two chases back to back.

your post makes one reluctant to take the risk though

Victor

Are shur inertia is a great thing, until...