HomeMy WebLinkAboutA009 - Memo dated Dcember 4, 1992 to City Council - tie-dow regulations from State Fire Marshall ANES
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TO: Mayor, City Coun
FROM: Brian P. O'Connek, irector, Planning & Housing Department
DATE: December 4, 1992
RE: Tie-Down Regulations
Please find attached a copy of a memorandum that has been provided by
the Building Code Engineer from the State Fire Marshall's office.
This memorandum indicates the number of tie-downs that would be
necessary to meet the "wind load standards" of site built homes as
required in the Uniform Building Code.
In discussing this issue with the State Building Code Engineer, it was
indicated that most manufactured homes, that are constructed currently,
exceed the number of tie-downs that are necessary to meet the wind load
standards for site built homes. But the problem arises not from a lack of
tie-downs, but rather from the method by which the manufactured home is
built.
According to the State Building Code Engineer, the manufactured home will
crush against the tie-downs or shear from the frame before the tie-downs
dislodge from the anchoring system.
In light of this situation, there is nothing to be gained by increasing the
number of tie-downs since the safety of the mobile home will not increase.
If the belief of the City Council is that an increase in tie-downs will
substitute as a safety measure in lieu of a shelter requirement, it is not
necessary to increase the tie-down standard since there is little to be
gained by doing so.
If the increased tie-down standard is designed to accomplish some other
public purpose, then creating an ordinance amendment to increase
tie-downs can be prepared by City staff for further consideration by the
City Council.
Attachment
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h\bpo\caf\memo.d04
12-0,4-92 08: 56AM FF' N! IOWA ST FIRE MARSHAL r' i
TO: Mr. B. O'Connell Planning and Housing Department -
Ames, Iowa
FROM: C. E. Peter Green - Building Code Engineer
DATE: December 3, 1992
SUBJECT: Tie-down systems for manufactured homes to meet an
80 mph wind load horizontal and I$ mph wind load
uplift.
TABLE A
(Based on 2,000 psi gearing Capacity of Soil)
mobile Home IMinimum, Number of Tie-downs per si a to
Box Length meet Iowa Wind Loads
Not Exceedingal Tieg Vert cal Ti *
731. dig
64' Q"
* The manufacturer may have a greater number of vertical ties
with each one of their units if this is so, then each tie must
be connected to an earth anchor.
The above table will meet the wind load standards in the Uniform
Building Code, 1991 , however for further safety and to prevent
longitudinal movement of the unit, each corner should have a
diagonal tie.
The U. S . Department of Housing and Urban Development took over
the manufactured (mobile) housing program effective July 15,
1976 , so the State or local jurisdictions have no authority to
alter any unit labeled as meeting the HUD Construction Standards .
The HUD Wind Load Standards for Iowa (zone 1 ) ( 15 psf
horizontal/9psf Uplift) which converts approximately into a 50/55
mph horizontal wind load and 28/29 uplift. It is possible to
increase by 5/7 mph the capacity of the unit to resist wind by
increasing the vertical ties in the table by two or three,
however making sure that the ties are attached to the structural
framework.
At a recent meeting in Washington, D. C. with HUD representatives
(which I attended) a general agreement was accomplished, that HUD
would review the wind loads in their standards for possibly
amending them to Model Code Standards . Another problem to be
resolved is the snow load differences between the Model Codes and
HUD. RECEIVED