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Re: 1-3/4" roof slab (smooth plaster finish)

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Dear Lew,

  The bottom plaster will not have any expanded
metal. My cement plaster finish will have a
final coat of smooth cement finish as per your
comments.

Thank you for your comments again. This
listserve  is really great.

Bye for now until next time.


Sincerely Yours,


ALEX C. NACIONALES, C.E
Iloilo City, Philippines




Lew Midlam wrote:

> I misunderstood.   I thought the expanded
> metal you were referring to was the 6 mm bars.
>
> The cement plaster you refer to is what we
> call 'stucco' here in Florida, and it is
> always
> considered non-structural, and is not
> considered corrosion protection for the
> reinforcing,
> because of its porosity.
>
> It's likely that the delamination I discussed
> previously will occur, and then the cover over
> the
> 6 mm bars will only be about 3/4".
>
> One last comment -- if the bottom plaster is
> also based on expanded metal, make sure the
> metal
> is mechanically fastened to the slab in such a
> way that the fastening will hold up the entire
>
> weight of the 3/4" plaster.  I've seen this
> type of construction become fully delaminated
> due to
> corrosion of the metal lath, and a 10 FT x 20
> FT section of the 3/4" plaster/stucco (about
> 1,500
> pounds) came crashing down.
>
> Regards,
>
> Lew
> =======================
>
> Alex C. Nacionales wrote:
>
> > Dear Lew,
> >
> >   The  1-3/4" slab is reinforced with 6mm @
> 4"
> > o.c. short span and 8" o.c. long span.
> > The 6mm steel is placed at the center of its
>
> > thickness. The bottom slab will  also be
> > plastered with 3/4"  1:3 cement plaster mix
> > although the structural function of the
> bottom
> > plaster is neglected.  Top and bottom cover
> is
> > 1.5" which is the  minimum allowed except
> for
> > the expanded metal which has only 1/2"
> cover.
> >
> > Thank you for your comments and best
> regards.
> >
> > Sincerely,
> >
> > ALEX C. NACIONALES,C.E.
> > Iloilo City, Philippines
> >
> > Lew Midlam wrote:
> >
> > > In my opinion, you have a 1-3/4 thick
> > > UN-reinforced concrete slab, with   1"
> of
> > > dead load
> > > plaster on top of it.  The plaster wil not
>
> > > provide sufficient corrosion protection
> for
> > > the
> > > metal, and in a few years it will corrode
> and
> > > expand, resulting in delamination of the
> > > plaster
> > > from the concrete slab.
> > >
> > > If this is the case, then the dead load of
> the
> > > plaster + the 30 PSF live load would cause
> the
> > >
> > > concrete to be over-stressed.  However,
> note
> > > that UN-reinforced concrete is not
> permitted
> > > for
> > > this type of construction (ACI 318-95,
> para.
> > > 22.2.2).
> > >
> > > My $.02
> > >
> > > Regards,
> > >
> > > Lew Midlam
> > > ==============================
> > >
> > > Alex C. Nacionales wrote:
> > >
> > > > Dear Lew,
> > > >
> > > > The 1-3/4" slab is one way and supported
> by
> > > > 6"x12" RC beam on fours sides. The slabs
> and
> > >
> > > > beams were poured first then the
> expanded
> > > metal
> > > > was placed on top of the slab and
> > > > and cement plaster 1:3 mix of washed
> sand
> > > and
> > > > portland cement type I was applied and
> > > cured.
> > > > Construction is complete now. I will
> send
> > > you a
> > > > picture if you are interested.
> > > >
> > > > Sincerely
> > > >
> > > > ALEX C. NACIONALES, C.E.
> > > > Iloilo City, Philippines
> > >
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