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Re: Ceilings/soffit panels

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Steve Privett wrote:

> I'd be concerned with adding any weight to the
> bottom chord of the roof
> trusses. Typically, they are designed as
> tension members and don't carry
> the additional loads.  What I've done in the
> past with similar
> situations, is to support the soffit structure
> at panel points of the
> trusses.  This at least keeps the members
> loaded axially but sometimes
> requires a heavier soffit structure.  In
> addition, with the installation
> of a soffit structure, there will probably be
> light fixtures, and
> insulation added so these too add to the
> weight.
> If there is existing plaster or other finish
> material at the existing
> finish ceiling line, the removal of it might
> be a consideration to keep
> the loads to the trusses close to original
> design loads.  Especially if
> you can design the soffit to load the trusses
> in a manner similar to how
> the existing higher ceiling loads are
> transfered to the trusses
> Otherwise you may be looking at reinforcing
> the truss members and/or the
> connections.. Especially the heel connections.
> I've had a tough time making most older
> trusses "work" when calced with
> the addition of any loads.... Sometimes they
> don't work even with the
> existing loads...  Are these like the 70 mph
> driving range screens built
> in the 110 mph zone??
> You might also consider metal framing... It is
> lighter than wood
> Steve Privett CE

I had a project were we replaced the existing
rotted wood curved ceiling of a church w/  1.5"
ferrocement reinforced with 6mm bars at  4" o.c.
bothways and metal lathe on both sides and is
framed with open web joists at 1.00 o.c. AllThe
existing steel trusses were reinforced  a curved
concrete beam. This ceiling can
support live load of  20 psf.  Ferrocement is
more durable and you can have decorative finish
on the cement for better accoustics.

Alex Nacionales, CE