Notching Roof Joists

If the cut outs are too large or in the wrong location the joist can be weakened and unable to support the load it was designed for.

Notching roof joists.

Rules for notches in joists. These joists may need reinforcin g to reduce bounciness sagging or excessive deflection in the floor or ceiling. Centre line 0 25 0 4 x span. Maximum notch depth in the outer third of a joist is one sixth of the joist depth.

It s important to calculate the siz. No notching in the middle third of a joist. Cutting notches and drilling holes in joists as part of any new installation work or a re wire a cable trunking or cable tray sometimes has to pass through an element of building construction such as a floor wall or beam necessitating the formation of a notch or opening in the element. Holes may only be made on the joist s centreline within the permitted area to a maximum diameter of 65mm.

Notches should be no deeper than 0 125 times the depth of the joist. Top edge 0 1 0 2 x span. 0 15 x depth of joist. 0 25 x depth of joist.

Additional holes must be at least three diameters centre to centre apart. Notches can only be made in the top or bottom of the joists not both within the permitted area to a maximum of 35mm. Drilling joists up to 250mm depth. The maximum depth of a notch at the end of a joist where it rests on a wall or beam can t exceed one quarter of the joist depth.

While it is a good idea to replace rotted material with 2x8s it may require some notching to fit between the sub floor and ledger board. Over notching or not jacking enough generally newer home floor joists are made from 2x8s or new engineered i beams older homes however may have 2x6s instead. In this diy guide you will learn how to install a roofing joist or rafter that includes how to work out the pitch of a roof cut a ridge or plumb cut at the correct angle work out the correct length of joist you need and the exact location for a birds mouth joint how to correctly cut a birds. Please follow these rules when notching joists.

Limit the length of notches to one third of the joist depth. Notching joists up to 250mm depth. Roger goes over the best practices and rules for notching and drilling holes in joists while filming our bathroom series. Sometimes joists are notched at the end where they bear on a wall or sill.