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RE: Reroofing

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I would also strongly agree with this. Oftentimes, small items or items
which are deemed unimportant are
neglected for calculations and serious thinking. But these small items are
where damage results. I would suggest that calculations be done even on a
personal basis. Don't depend on rule of thumb or "common practice" rules. I
have known of some situations wherein the engineer-in-charge depended on his
own "engineering judgement" and not on thorough analysis and computations.
The results were 1.) uneconomical design (" If it's not economical, it's not
engineering) 2. Rectification of work. (Chipping of concrete, weld removal
including member removal) 3. Sleepless nights for the structural engineer or
engineer-in-charge.

All I've written does not apply only to roof but to all parts of the
structure included in the responsibility of the structural engineers.

A. Yango
Civil/Structural Engineer
Philippines

> ----------
> From: 	vicpeng[SMTP:vicpeng(--nospam--at)vtcg.com]
> Reply To: 	seaint(--nospam--at)seaint.org
> Sent: 	Thursday, April 15, 1999 8:50 AM
> To: 	seaint(--nospam--at)seaint.org
> Subject: 	Re: Reroofing
> 
> Whether it calcs or not it would be wise to strongly recommend that a
> structural engineer review the impact of the change of roof material.  If
> the building authority still insists that is unnecessary then you may have
> an ethical obligation to register your serious concerns.  Then if
> something
> happens you can say, "I told you so".
> My $.02
> 
> Thor Tandy  P.Eng  MCSCE
> Victoria BC
> Canada
> vicpeng(--nospam--at)vtcg.com
> 
> -----Original Message-----
> From: Tom.Hunt(--nospam--at)fluordaniel.com <Tom.Hunt(--nospam--at)fluordaniel.com>
> To: SEAINT(--nospam--at)seaint.org <SEAINT(--nospam--at)seaint.org>
> Date: Wednesday, April 14, 1999 11:44 AM
> Subject: Reroofing
> 
> 
> >     Our homeowners association is planning on reroofing our entire
> complex
> >     of 165 buildings (4 to 5 units per building).  They have narrowed
> the
> >     options down to 5 roof coverings all of which are class A concrete
> or
> >     clay tile.  The most likely choice will be "ClayMax" by US Tile on
> >     plywood sheeting.  The existing 20+ year old roofs are cedar
> shingles
> >     on what looks like 1/2 inch by 6 inch planks spaced about 12 inches
> >     o/c (you can see 4 to 6 inch of the black paper between the planks).
> >
> >     The new roof system is obviously heavier than the existing system
> and
> >     therefore will generate more seismic load to the shear walls.  I was
> >     shocked to learn that the city of Irvine has a "city policy" that if
> >     the clay tiles (EXCLLUDING the addition of plywood) are less than
> 7.5
> >     psf then NO structural calculations are required.  The ClayMax tiles
> >     weight 5.8 psf.
> >
> >     The city official I talked to said that since the plywood would add
> >     "extra seismic rigidity" they discount the added weight of the
> >     plywood.  I politely explained that with the 3 to 4 psf added to the
> >     roofs from the new tiles and plywood the shear walls will be taking
> >     more seismic load regardless of the roof rigidity.  His comment was
> >     that since the buildings are 20+ years old they would never "calc
> out"
> >     with the added weight and newer codes.  Duh!!
> >
> >     For those with conventional construction and reroofing experience (I
> >     am a concrete/steel guy) is it normal not to require structural
> >     calculations when reroofing with a heavier system.  Without
> structural
> >     calculations I would think as a minimum this could void our
> earthquake
> >     insurance.
> >
> >     Every time we have a good shaker I get cracks around the door
> openings
> >     and it seems this will only make it worse.  Any other comments on
> >     reroofing concerns/problems??
> >
> >     I should also note that we are located on a slight hill and each
> unit
> >     is half slab on grade and half elevated.  The elevated half is about
> 6
> >     feet above grade.
> >
> >     Thomas Hunt
> >
> >
> >
> 
> 
> 
>