Holes, Notches and Chases

by Steve on November 5, 2009

Holes, Notches and Chases

 

Building Regulations   Part A –  Structure

 

Holes and Notches in Wooden Joists

 

  • Maximum diameter of hole should be 0.25 of the joist
  • Holes in centre line in a zone between 0.25 & 0.4 of joist span
  • Maximum depth of a notch should be of 0.125 of joist depth
  • Notches on top in a zone between 0.07 and 0.25 of joist span
  • Holes in the same joist should be at least 3 diameters apart

 

A diagram of these dimensions can be found in The Electrician’s Guide to the Building Regulations (listed below).

 

Roof Rafters

No holes or notches should be cut into roof rafters other than at supports where the rafter may be birdsmouthed to a depth of 0.33 of the rafter depth.

 

Chases

Verticle

Verticle chases should not be deeper than a third of the wall thickness.  Cavity walls- one third of the leaf or inner brick surface.

 

Horizontal

Horizontal chases should not be deeper than a sixth of the wall thickness.  Cavity walls- one sixth of the leaf or inner brick surface.

 

Chases should not be run so as to impair the stability of the wall.

Especially where the construction uses hollow blocks.

 

 

Source information:

 

Find related information:

Electricians and The Building Regulations

 

The On-site Guide for Electricians

 

ElectriciansBolg.co.uk

 

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