Soffit Suction Pressure
Soffit Suction Pressure
(OP)
How do I go about calculating the suction pressure on the eaves of a roof to determine the attachment of the soffit material? I know there are tables that spell out the attachment of the soffit based on the wind speed but I would rather calculate the pressure myself and determine the attachment.






RE: Soffit Suction Pressure
RE: Soffit Suction Pressure
RE: Soffit Suction Pressure
DaveAtkins
RE: Soffit Suction Pressure
If there is suction at the top of a wall, there has to be suction on the adjacent soffit. Similarly with positive pressure on wall, then uplift on soffit. You can't go from positive to negative without transitioning through zero.
RE: Soffit Suction Pressure
DaveAtkins
RE: Soffit Suction Pressure
RE: Soffit Suction Pressure
RE: Soffit Suction Pressure
RE: Soffit Suction Pressure
ASCE 7-05 is not clear on the subject; however, for some hard data and conclusions see the paper by Vickery entitled "Component and Cladding Wind Loads for Soffits", ASCE Journal of Structural Engineering, May 2008.
From conclusions section of the aforementioned paper:
"The results of the experimental program clearly indicated that wall and soffit pressures are highly correlated....The results indicate a simple and accurate solution to the soffit loading deficiency in ASCE 7 is to prescribe that the component in cladding pressures (both positive and negative) for use in the design of soffits be identical to the component and cladding loads used for the design of the wall components."
RE: Soffit Suction Pressure
kslee, suction is just the pressure on one side of a surface. You do sum the pressures on both sides of a wall for design, but a soffit will usually only see the external pressure, as the top of the soffit is in the enclosed roof cavity. You do get upward pressure on soffits on the windward side, but on the leeward and side wall, the soffit pressure is usually suction.
RE: Soffit Suction Pressure
I understand and appreciate your explanation (side walls making sense). Thanks.