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Covered Patio Not built to Code– 2015 IRC R401.3 Drainage Exception 2% Slope

AMH

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Joined
Aug 6, 2022
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4
Location
OK
R401.3 Drainage.

Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall not fewer than 6 inches (152 mm) within the first 10 feet (3048 mm).

Exception: Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152 mm) of fall within 10 feet (3048 mm), drains or swales shall be constructed to ensure drainage away from the structure. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.
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We believe our concrete patio wasn’t built to code. I have posted the IRC 2015 code for drainage above, as this is the code the city, we live in has adopted. We believe the 2% slope requirement applies to covered or uncovered concrete patios because the code doesn’t exempt covered patios. Our General Contractor doesn’t believe it applies. Our local code inspector doesn’t either, but it is a small city, so they don’t inspect slabs/patios, so I don’t think he is really informed. I have contacted a couple of larger municipalities near us and they have both told me it doesn’t matter if the impervious surface is covered or not covered the slope requirements in R401.3 apply to both.

Are we correctly interpreting the code that it should have been poured with a 2% and not level in the first 10'? Where can I find information to back up that R401.3 wasn’t met? I need something more than my opinion and the opinion of a couple of local code inspectors to convince my GC this is something that needs to be fixed.

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It isn't letting me attach a picture. Here is a little background on the patio.

The concrete patio area is 20’ x 15’ with two sides against the house. There is a sliding door on the 20’ section and a single door on the 15’ section. We asked for a walk-out patio and not a step-down. The GC’s subcontractor unfortunately didn’t slope it much, so it doesn’t drain well. They sloped it a total of 1.5” over a span of 25’ - from the corner where the wall of the addition meets the existing house to the far corner of the patio. However, the 1.5” slope doesn’t really start to slope until the middle of the patio. Therefore, the patio is level near the house. In fact, the first 10’ of the patio from the addition wall and also the existing house is flat and level. Some areas of the patio are level for 20’. It is basically flat enough that you could easily build on it.

The concrete is mostly covered but there are a few feet that aren’t covered. Since it was poured a month ago, we have only had light showers and already water puddles and slowly back-ups toward the middle of the patio because it is too flat for it to drain off. It then takes hours for the water to evaporate off the patio even though we live where it is 100+ in the summer. We live where we get thunderstorms where water blows, so I foresee water blowing in under the covered area. Not draining is concerning to us, especially because we asked for a walk-out patio, making it much easier for water to back up into the house without the proper slope. We also get freezing rain and freezing temperatures in the winter which could result in the patio becoming an ice skating rink.

Making things even more complicated is the patio had 3 columns that support the roof, so replacing the patio is going to be a huge challenge.
 
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AMH, ...Welcome to The Building Codes Forum ! :)

Q1): Were there any reviewed \ approved plans for your project ?
Q2): Is there a Building Official that you can go and discuss this
matter with ?


= $ = $ =
 
Did you jave full architectural drawings for the build? Did they include spot elevations for the patio?
 
The code absolutely applies. I have encountered nearly the same situation….I say nearly because an owner asked about the slope before the contractor placed the concrete. The owner didn’t want a slope of any dimension and the contractor was insistent that 2% slope is a minimum requirement. The owner asserted that because the patio was a covered patio, no rain would ever land on the concrete. I explained that patio covers come and go but rain is forever….and the code does not have an exception for a patio cover.
 
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$ = $ = $

AMH, ...Welcome to The Building Codes Forum ! :)

Q1): Were there any reviewed \ approved plans for your project ?
Q2): Is there a Building Official that you can go and discuss this
matter with ?


= $ = $ =
There were some basic plans for the structure, but not a lot of details about the patio other than size. The small city we live in doesn't require very detailed plans. The slab was the very beginning of the project and we before realized our GC isn't as knowledgeable as we thought. We have since started asking a lot more questions. Little to no discussion took place between us & the GC prior to the slab pour other than we didn't want a step-down. On the day of the pour, the GC wasn't there (which has pretty much how the entire project has gone). I had subs knocking on my door asking me questions. It has become obvious to us as the project has gone on the GC is way too trusting of the Subs and gives them very little feedback. At that time I didn't even know about the 2% slope code or I would have inquired with the GC or subs.

The local building official who inspects things is a nice guy but he doesn't know what he is talking about when it comes to this matter. The City doesn't inspect slabs just the footing so this isn't something he deals with. He took it upon himself to read the Code, interpert it and respond to the GC's email that covered patios don't apply to the code. That is when I contacted two nearby metros and their building inspectors told me the code applies to both covered and not covered.
 
Did you jave full architectural drawings for the build? Did they include spot elevations for the patio?
The GC did the plans, and they were just basic drawings for the addition. No information about the patio except size. After framing started we found errors in the plans, some of which were fixed, and other smaller things that we have let go of. The plans have ended up be a "guideline" The entire project has been a bit of a mess.
 
The code absolutely applies. I have encountered nearly the same situation….I say nearly because an owner asked about the slope before the contractor placed the concrete. The owner didn’t want a slope of any dimension and the contractor was insistent that 2% slope is a minimum requirement. The owner asserted that because the patio was a covered patio, no rain would ever land on the concrete. I explained that patio covers come and go but rain is forever….and the code does not have an exception for a patio cover.
Exactly. This is our take on it too, but we are trying to figure out how best to explain/convince the GC this is true when our local building inspector isn't familiar with this part of the code and has told them covered patios don't apply.
 
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