joist hangers / constructional hearth

I can't make out what you are on about here, can you draw a picture using mspaint and send it to tinypic?

the short throw is to get the joist in when only a 125mm slab. can't have spur at top because it has to be well below surface of concrete to properly fix it.

made, which would cost one upper and one lower limb. Why can't the joists go into the newly constructed hearth? - or why can't they go on conventional joisthangers affixed to it?

It is not a completely new constructional hearth, the dimensions of the old one are sufficient so long as the joists do not enter it. Hence the hangers. The joists can't go on conventional hangers because the pronged point which would be incorporated in the cast concrete would be too close to the surface and would likely break loose in a short time. This is all to be done with existing floor in situ. I'm looking for a simple solution.

There are some hangers that you can fold the fifing point. But I don't know if the gauge is upto it. There seems to be 2 grades of hanger, I don't know when to use each type.

If you did choose the above hanger, I'm assuming that you will be concreting the hearth afterwards flush with the level of the floorboards? - if so, you will gain extra strength because the top of each one would be under 18mm of fine concrete.

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Excellent!

They're made by one of his organ banks in sector 7G. :-p

I'm just concerned that they would turn to custard and a voice would be heard "hah-hah"

-- Mike W

they are 460mm, but the joists are ? - about 200mm? - then across the top of the wall will eat up another 100mm....180mm down the other side, should be ample, but better still if you twist the 180mm into a 'pig's tail' kind of shape and cast concrete over the top and screw the parts on top of the wall into the brickwork.