Today I was asked to assist a Public Health Official with background information on swimming pool floor slopes. Specifically, they were looking for the reasoning behind 1:12 slopes for zero depth entry pools and why 1:3 is the maximum desired slope for the deep to shallow floor transition.
Americans with Disabilities Act (ADA), 1994
The ADA affects several Federal Agencies but this discussion is limited to swimming pool floor slopes which are primarily governed by the United States Access Board that is responsible for accessible design. The Department of Justice publishes the ADA Standards for Accessible Design (Code of Federal Regulations 28 CFR Part 36, revised July 1, 1994) that addresses items such as wheelchair access dimensions and floor slopes.
The ADA Standards do not address pools and spas except for the requirement that the edges of reflecting pools shall be protected by a detectable warning (e.g., curb, railing, etc.) and benches near pools shall not accumulate standing water and shall be slip-resistant. The Access Board does publish ADA Accessibility Guidelines for Recreational Facilities; however, these guidelines are not enforceable because they are not incorporated into the Department of Justice accessibility standards.
The guidelines do address lift chairs, ramps, handrails, and other details. The maximum slope of the ramp is 1:12, the minimum depth is 24″ and the maximum depth is 30″ at the bottom of the ramp.
International Building Code (IBC), 2006
The IBC does not address accessibility for pools or spas, although some states have amended the IBC with requirements that are similar to the Access Board’s Recreational Guidelines. California, for example, utilizes the 2007 California Building Code (CBC) which is the 2006 IBC with specific amendments. For public pools, CBC Section 3104B points to Section 1102A.5 which points to Section 1141A that describes lift chairs.
The CBC does not specifically list 1:12 ramps for pools but the Department of Environmental Health has generally accepted a ramp as an alternative to a lift chair when a waterproof wheelchair is provided by the facility. IBC Section 1010.2 limits the slope to 1:12 (8.33%) and Section 1010.4 limits the rise of any ramp to 30″ maximum. CBC Chapter 11B also includes several diagrams regarding wheelchair turning radiuses, minimum and maximum widths, slopes, cross-slopes, and other criteria.
Maximum Transition Slopes
Imagine a swimming pool with sidewalls that are not vertical, but sloped 30 degrees from vertical. It would be hard to get out of a pool configured this way. The slope prevents the swimmer from being able to get their body into a vertical climbing position, and it is also too steep to stand on and walk out. The ANSI/NSPI-1 and ANSI/NSPI-5 Standards for Commercial and Residential Pools, respectively, include requirements for maintaining almost vertical walls to a minimum depth of 2′-9″ for this reason.
Similarly, if the slope of the floor in the transition from deep to shallow water is too steep, it might make egress more difficult. For most people it is easy to simply swim to the shallow depth, but we can’t make the assumption that everyone can swim. If someone is treading water at depth and then they try to move to the shallow area, a steep sloping floor may get in the way of their feet but also be too steep to stand on – the swimmer is essentially prevented from getting to the shallow area.
ANSI/NSPI-1 and ANSI/NSPI-5 both address this by limiting the slope to 1:3 (33.3%) maximum in Sections 6.3.4 and 5.6.3, respectively. The IBC does not address this issue, but the CBC adds Figures 31B-1, 31B-2, and 31B-3 which all indicate a maximum transition slope of 1:3 for commercial pools.
Flat Area Slopes
Any perfectly flat, non-sloped, area in the pool will be more difficult to plaster due to standing water and could potentially be a collection area for dirt that is not otherwise transported by gravity toward a drain. Therefore, it makes sense to have at least a mild slope for any floor. We use a 1/8″ per FT (1%) slope as a minimum slope for areas that are intended to be primarily level. This is no different than the decking around the pool where 1/8″ to 1/4″ per FT slopes to drains or the edge of the deck are typically used to eliminate standing water.
Certainly, in a pool, a much greater slope can be used and it won’t result in the patio furniture sitting at an angle or on three legs only. But, unnecessary slopes can be annoying when you are trying to walk around and enjoy a consistent depth for exercise or especially for children where a few inches of water depth can be the difference between breathing and choking on the water. When we want a shallow area, we are deliberate about it – we don’t get lazy and allow the transition slope to start to bending down too early.
Not surprisingly, the ANSI/NSPI Standards have something to say about shallow area slopes. ANSI/NSPI-1 requires a 1:12 maximum slope for Class B pools (public recreation), and a 1:10 maximum slope for Class C pools (apartments, condominiums, HOAs). ANSI/NSPI-5 requires a 1:7 maximum slope for residential pools.
My Recommendations
Personally, I think that any slope over 1:12 feels too steep and uncomfortable to walk on. We use the 1:12 for ADA access in commercial pools as well as zero depth entry pools for private owners. Once we outline the extents of the shallow area(s) we try to keep as much of that area as flat as possible. Below 3 FT of water depth we can use slopes up to 1:3 which will still meet the codes and standards.
- Steps and Benches: 0:12 to 1/8:12 (0 – 1%), usually expressed as level to 1/8″ per FT
- Flat Areas: 1/8:12 to 1/4:12 (1 – 2%), usually expressed as 1/8″ per FT to 1/4″ per FT
- Top of Submerged Vanishing Edge, Slot Edge, or Perimeter Overflow Walls: 1/2:12 to 1:12 (4 – 8.33%)
- Zero Depth Entries: 1:12 (8.33%)
- Sand Beach Entries: 1:12 (8.33%)
- ADA Access Ramps: 1:12 (8.33%)
- Deep to Shallow Transition Slopes: 1:3 (33.3%)
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