Floor joist depth

[garrymum]

Hi guys

I know the answer to this cannot be 100% accurate but would appreciate your comments, especially those who work on new house builds.

Does anyone know what depth a first floor, floor joist would be? As with all newish houses the floor is chipboard so it's not as easy as lifting a floor board to have a look. House was built in 2000/01.

Reason I ask is I am redoing my ensuite and want to know if I can route the shower waster through the centre of the joists. Maximum allowable hole is 0.25 x depth of joist.

Is there a standard for the minimum depth allowed on newish properties?

Thanks

 

[noseall]

your floor joist depth will be dictated by room with the greatest span.

you can sometimes work out the depth at the stairwell trim.

 

[anobium]

As a general rule of thumb the overall length of the joist span, divided by 2 +1, equals the depth of the joists.
eg, joists spans 14 ft, wall to wall, dived by 2 +1 = 8. Therefore joist depth is 8 inches.
Note this only works in imperial and is for domestic loadings only.

 

[^woody^]

The most common joist depth is 200mm, with 175mm and 220mm less common.

As mentioned, you can normally see the floor thickness at the staircase opening, and work it out from there