Slope for Exterior Balconies

[aaronm]

Codeman:

In the past I asked you about the required slope away from buildings for exterior balconies. You responded rather vaguely with ACI 318 and 1/4" per linear foot. Can you be more specific?

[Jerry Peck - Codeman]

Hi Aaron,

The only times I have seen more specificity has been on contract documents such as drawings, details, and specifications.

In those cases what I've seen specified has been ' minimum 1/8 inch per foot slope ' and sometimes that is accompanied with ' maximum 1/4 inch per foot slope '.

Those are based on the widely accepted minimum surface drainage slope of 1/8 inch per foot and that any slope greater than 1/4 inch per foot (either in the direction of travel - i.e. "running slope", or perpendicular to the direction of travel - i.e. "cross slope") of a walking surface is potentially a hazard to persons using the walking surface.

I have not yet found a code which specifies a maximum slope, other than for accessibility purposes (i.e., in the ADAAG - place cursor over link, right click, select 'Open in New Window': http://www.access-board.gov/adaag/html/adaag.htm ), which specifies a maximum slope of:
- 4.3.7 Slope. An accessible route with a running slope greater than 1:20 is a ramp and shall comply with 4.8. Nowhere shall the cross slope of an accessible route exceed 1:50.

A slope of 1:50 is approximately equal to 1:48, and 1:48 is 1/4 inch per foot. Balconies would need to meet the 1:50 maximum slope for either direction as people could be walking either direction where accessibility is addressed.

[aaronm]

Thanks!

[aaronm]

JC: Found this - cost me $25 from ACI -
ACI 302-96, “Guide for Concrete Floor and Slab
Construction,” states that “positive drainage requires a
slope of 1/4 in. per ft (20 mm/m) for an exterior slab; for
an interior floor slab, 1/16 in. per ft (5 mm/m) minimum
is adequate for drainage, but 1/8 in. per ft (10 mm/m) is
preferred.”