In article , Dg wrote:
Although I agree that use of such a beam is a bad idea, it is
interesting to note the many houses built up to the mid 60's with
first floor walls built off a single or doubled timber joist.

Yes, but double joists nailed together have a lot of lateral
stiffness when compared with one of IMM's TJI beams which are
basically 50x50 top and bottom with a ply web.


Walls built off timber from new would settle naturally, but its a
different matter when retrospectively fitting a timber support in
situations like this.

Quite so: on site you'd put the beam in and build the wall up -
probably in lime mortar - and as the beam deflected under the weight
the mortar would accommodate this. If you put a beam under an
existing wall you need to properly preload it or there is a risk that
over a period the weight will gradually shift to the beam causing
cracking. This would be far more likely with timber which (a)
deflects more - deflection is usually what governs timber member
sizing; and (b) creeps: put x tons on a steel beam and it deflects by
y .. and never moves any further; put x on a timber and next
week/month you'll find that the deflection is more than it is now.

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