Shallow depth joists?

[tony1851]

Tony, would the maximum span size alter if the joists were for a loft floor? For example if the span was 4.0mtrs but you could never actually walk on 1.5mtrs of it due to a pitched roof?

The normal loading for domestic floors is 1.5kN/m² (30 lbs sq/foot when I were a lad). But logic says that in a loft, it's almost impossible to load the whole floor area up to that level because of the low eaves. I understand there's been research which shows that domestic floors, and even office floors, rarely carry that level of loading, but I've not been able to find it.

In some cases where standard floor joists were marginal, I've suggested to building control that we reduce the load within a certain distance of the eaves to - say - 1kN/m². With little number crunching, this can often result in shallower joists, thus giving just a little more headroom.

 

[Ian H]

The normal loading for domestic floors is 1.5kN/m² (30 lbs sq/foot when I were a lad). But logic says that in a loft, it's almost impossible to load the whole floor area up to that level because of the low eaves. I understand there's been research which shows that domestic floors, and even office floors, rarely carry that level of loading, but I've not been able to find it.

In some cases where standard floor joists were marginal, I've suggested to building control that we reduce the load within a certain distance of the eaves to - say - 1kN/m². With little number crunching, this can often result in shallower joists, thus giving just a little more headroom.

Thanks, and a totally unrelated question, do those hollow blocks used to make internal walls ‘back in’t day’ have any structural qualities? Daughters looking to add storage space in the loft but the centre wall is made of them with a 4x3 mortared on the top.