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RE: Unit weight of precast roof plank from 1960

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Back in the old days there were several products used that were referred to
as structural roof materials such as:
	Cement Roofing Tile
	Thermo Slab Tile
	Federal Cement Tile
	United States Gypsum made several products
	Zonoloite Concrete Roof Deck
	Celotex Cemesto Roof Deck

If it is called out as a 3" Precast Roof Plank, I would guess it to be a USG
product which would have a DL of 17 psf or the 3" Zonolite is listed at 15
psf.  I would check the density to be sure.

Many of these products contained asbestos.  I would have it tested.

Harold Sprague

> -----Original Message-----
> From:	mark swingle [SMTP:mswingle(--nospam--at)]
> Sent:	Friday, June 02, 2000 3:44 PM
> To:	seaint(--nospam--at)
> Subject:	Unit weight of precast roof plank from 1960
> We are investigating an existing building in Massachusetts, built in 1959
> and 1964, to which an addition is currently being attached.  It is a
> one-story building which framing consists of open-web joists at 4' oc
> supported by steel beams and columns on spread and strip footings.
> Exterior walls are CMU infill.
> The existing drawings call out <3" PRECAST ROOF PLANK> spanning the 4 ft
> between joists.  Does anyone know the unit weight of this material?
> Breyer's 3rd edition lists <concrete plank> at 6.5 psf per inch, which is
> 78 pcf.  Regular-weight concrete is 145 pcf.
> Is Breyer correct?  Is this the same thing?  In other words, was
> light-weight concrete in use for roof planks in 1959 and 1964?
> By the way, if I use 145 pcf, some of the existing joists and beams are
> overstressed, which seems unlikely.
> Any history lessons from you old-timers will be greatly appreciated.
> TIA,
> Mark Swingle, PE, SE