Joist Hangers on Joist supported on Joist Hangers...?

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As per title really - is it ok to hang joists on a joist which is already supported at either end on joist hangers?

I'm looking to get rid of the ugly timbers which are below ceiling level under a flat roof which is part of an extension from many years ago (1980's). It's a bungalow and the flat roof is at the front before where the pitched (original) starts. The room is 3.6m wide and 4.4 front to back. Currently there are 4x2 joists running front to back which sit on a wall at one end and two HUGE 10"x4" timbers 2.7m away which also support the 6x2 that span 1.5m from the front of the flat roofed extension.

At the sides there are joists running along the top of the walls in line with them (above ceiling height and above the huge timbers) so I cannot get a steel (or timbers) to sit on the wall so one of the ways I thought about was to use hangers on the "side joists" that run the length of the wall and then use hangers of the joist that is hung between them. Or would that be too much effectively just on the side hangers?

Alternatively, does anyone know what size steel would be used to replace the two 10"x4" timbers? I can't find any tables etc anywhere.

Hope this makes sense, I've tried to describe the situation as best I can.

Thanks in advance for any help.

 

[Deleted member 174758]

In order to do this, the first joist should surely be considered to be a trimmer, in which case it would normally have to be doubled or even trebled to carry the additional loads you are talking about imposing on it. The alternative would be to move what you refer to as "side joists" (presumably end of room joists set close by a wall but with a small gap) so that they butt against the wall and are mechanically fixed to it using either Rawlbolts or resin anchors, thus becoming ledgers or wall plates, to which joist hangers can be attached. It is advisable for ledgers affixed to an exterior wall to.be made from treated ti.bervand to be separated from the masonry ry by the installation of a DPM between the ledger and the wall